Reversing gearbox final drive
Discussion
I have been working on my project car and have the Porsche 944 rear suspension fitted. This has now created a problem as the Peugeot engine will now not fir the corredct way round! It will fit if "reversed" but that would give me 1 forward gear and 5 reverse.
Is it possible to reverse the ring-gear or final drive in the gearbox to change the output direction of the box?
The engine is a XU10J4 (S16) out of a 306, with the standard gearbox.
Many thanks,
Jon
Is it possible to reverse the ring-gear or final drive in the gearbox to change the output direction of the box?
The engine is a XU10J4 (S16) out of a 306, with the standard gearbox.
Many thanks,
Jon
I have tried turning the gearbox upside-down and offering it back to the engine. Unfortunately both the differential housing and starter motor foul the block, none of the bolt holes line up either so that is out.
Does anyone know if there would be a FWD gearbox that spins the opposite way that could be adapted to fit? I think that some Mazda or Honda boxes spin the other way but am not sure.
Any help gratefully appreciated,
Jon
Does anyone know if there would be a FWD gearbox that spins the opposite way that could be adapted to fit? I think that some Mazda or Honda boxes spin the other way but am not sure.
Any help gratefully appreciated,
Jon
So you're using the Peugeot engine in a rear engine config, i.e. engine behind the rear axle?
You can't mod a FWD gearbox to flip the output direction relative to the input.
I'm not familiar with Honda's but am led to belive they run "backward" hence the engine is on the nearside of the engine bay. If you could adapt one of their gearboxes to your engine it would put your engine on the offside (once you've spun it around) and if I'm thinking straight at this time in the morning that should get you spinning the right way.
You could also rotate your gearbox through 180degrees about the input shaft to put the output at the front of the engine but sounds like you've tried that
You can't mod a FWD gearbox to flip the output direction relative to the input.
I'm not familiar with Honda's but am led to belive they run "backward" hence the engine is on the nearside of the engine bay. If you could adapt one of their gearboxes to your engine it would put your engine on the offside (once you've spun it around) and if I'm thinking straight at this time in the morning that should get you spinning the right way.
You could also rotate your gearbox through 180degrees about the input shaft to put the output at the front of the engine but sounds like you've tried that
beejay said:
So you're using the Peugeot engine in a rear engine config, i.e. engine behind the rear axle?
Yes exactly! I was going to go mid-engined with the FWD box but it doesn't fit, life is never the easy!beejay said:
You can't mod a FWD gearbox to flip the output direction relative to the input.
That's not the news I wanted to hear! I have been related a number of, probably hypocraful, stories about mechanics rebuilding gearboxes only to discover that they have reversed something and now have 5 reverse and 1 forward gear. Always a "friend told me" or "I have heard" though so I was suspicious.beejay said:
I'm not familiar with Honda's but am led to belive they run "backward" hence the engine is on the nearside of the engine bay. If you could adapt one of their gearboxes to your engine it would put your engine on the offside (once you've spun it around) and if I'm thinking straight at this time in the morning that should get you spinning the right way.
I think you might be correct and I may be searching for a Honda box to see whether I can make it fit.beejay said:
You could also rotate your gearbox through 180degrees about the input shaft to put the output at the front of the engine but sounds like you've tried that
Yes tried that but no go.Many thanks for the response,
Jon
Edited to correct formatting by Jonleeper on Tuesday 3rd February 09:09
Edited by Jonleeper on Tuesday 3rd February 09:10
Jonleeper said:
...That's not the news I wanted to hear! I have been related a number of, probably hypocraful, stories about mechanics rebuilding gearboxes only to discover that they have reversed something and now have 5 reverse and 1 forward gear. Always a "friend told me" or "I have heard" though so I was suspicious...
It's more likely that someone rebuilt their diff incorrectly!I wouldn't be using a normally-aspirated 944 gearbox, even with standard power engines, under normal use, they will break the teeth off the pinion gear or the cross-pin in the diff. The turbo gearbox is tougher, but the ratios are different.
If you are using the Peugeot gearbox, can you turn it upside down?
Some of the kit-cars use the Porsche G50 gearboxes turned that way.
If you are using the Peugeot gearbox, can you turn it upside down?
Some of the kit-cars use the Porsche G50 gearboxes turned that way.
Edited by D900SP on Tuesday 3rd February 10:16
The logical engineering answer is to scrub the Peugeot engine and run the Honda engine.
However I'm confused.
Where is the gearbox (car relative) and where is the engine?
It may be possible to rotate the gearbox, however don't go thinking it is just a case of flipping it over, I'm not sure if that box has an oil pump (I can tell you in a few days though as I'm breaking one down for scrap) also obviously drain plug and breather needs swapping over.
Explain the configuration of the car and I should be able to help, it's not the most outlandish job I've ever heard of.
However I'm confused.
Where is the gearbox (car relative) and where is the engine?
It may be possible to rotate the gearbox, however don't go thinking it is just a case of flipping it over, I'm not sure if that box has an oil pump (I can tell you in a few days though as I'm breaking one down for scrap) also obviously drain plug and breather needs swapping over.
Explain the configuration of the car and I should be able to help, it's not the most outlandish job I've ever heard of.
The basic floorpan is off an air cooled VW Beetle and is thus a strong centre tunnel with everything suspended from that. I have strengthened this with some box section around the external edge of the chassis as I also need to raise the body in order to release some more height inside.
The normal Beetle configuration is the engine slung longitudinally out the back behind the driveline powering the rear wheels through a trans-axle type gearbox. The rear suspension is provided by a torsion bar in front of the driveline using either swing arms or a lower wishbone system. I have fitted the lower wishbones from a 944 and wanted to use this suspension set-up as it is quite good and gives me uprated brakes and an easy handbrake system.
Various engine choices were considered but they centred on two main ideas. The first is to use an original VW Beetle or Porsche gearbox and sling the engine out the back. This has the advantage of accommodating the original suspension easily but places a lot of weight well behind the driveline. This is not a good thing and has taken Porsche a lot of time, money and effort to produce good results. The other option was to take a normal FWD engine and gearbox and mid mount them to drive the rear wheels. This gets more complex with the suspension but gives much better weight distribution. The Peugeot engine was going to sit, as it does in the 306, transversely driving the rear wheels through it's normal FWD gearbox matching the Peugeot driveshafts to the Porsche hubs. This would mean that the engine was, just, in front of the driveline and give me much better weight distribution over the normal Beetle. Unfortunately the space available is not great and it does not fit this way round, with the sump and engine ahead of the driveline. It does fit comfortably with the driveline ahead of the sump and engine but then the gearbox is trying to drive the car the wrong way. The weight distribution is also a little worse, as I am effectively going rear engined again, but nothing like as bad as if I was using a Beetle or Porsche gearbox.
There is the option of simply cutting off the torsion bar housing and building an engine cradle that incorporates the Peugeot strut tops and suspension sub-frame and fitting that onto the remaining Beetle chassis. This will fit, I've measured it, but means that I will have the original Peugeot front McPherson strut suspension at the rear of the car. I will also have to lock the steering arms off to prevent unwanted steering input and try to manufacture some form of handbrake. Now this is not impossible, and may be less work than any other solution, but I am trying to explore every option before I make any decisions.
I will try to get into the garage at lunchtime and take a couple of photos, a picture tells a thousand words and all that, to illustrate what I am trying to say.
Jon
The normal Beetle configuration is the engine slung longitudinally out the back behind the driveline powering the rear wheels through a trans-axle type gearbox. The rear suspension is provided by a torsion bar in front of the driveline using either swing arms or a lower wishbone system. I have fitted the lower wishbones from a 944 and wanted to use this suspension set-up as it is quite good and gives me uprated brakes and an easy handbrake system.
Various engine choices were considered but they centred on two main ideas. The first is to use an original VW Beetle or Porsche gearbox and sling the engine out the back. This has the advantage of accommodating the original suspension easily but places a lot of weight well behind the driveline. This is not a good thing and has taken Porsche a lot of time, money and effort to produce good results. The other option was to take a normal FWD engine and gearbox and mid mount them to drive the rear wheels. This gets more complex with the suspension but gives much better weight distribution. The Peugeot engine was going to sit, as it does in the 306, transversely driving the rear wheels through it's normal FWD gearbox matching the Peugeot driveshafts to the Porsche hubs. This would mean that the engine was, just, in front of the driveline and give me much better weight distribution over the normal Beetle. Unfortunately the space available is not great and it does not fit this way round, with the sump and engine ahead of the driveline. It does fit comfortably with the driveline ahead of the sump and engine but then the gearbox is trying to drive the car the wrong way. The weight distribution is also a little worse, as I am effectively going rear engined again, but nothing like as bad as if I was using a Beetle or Porsche gearbox.
There is the option of simply cutting off the torsion bar housing and building an engine cradle that incorporates the Peugeot strut tops and suspension sub-frame and fitting that onto the remaining Beetle chassis. This will fit, I've measured it, but means that I will have the original Peugeot front McPherson strut suspension at the rear of the car. I will also have to lock the steering arms off to prevent unwanted steering input and try to manufacture some form of handbrake. Now this is not impossible, and may be less work than any other solution, but I am trying to explore every option before I make any decisions.
I will try to get into the garage at lunchtime and take a couple of photos, a picture tells a thousand words and all that, to illustrate what I am trying to say.
Jon
No I understand exactly what you mean.
For some reason I assumed you were using the 944 box as well.
You have 2 problems as far as I can see and physically fitting it in is the easy one. Trickier is getting the gear linkage forwards (not hard if cable) and working smoothly.
In your position I would seriously look at going a bit more advanced but also ending up with a far nicer finish.
The Porsche 924/944 box is already designed to work in exactly that configuration it is designed to fit in what is basically a Beetle rear suspension and will of course fit the Porsche hubs/shafts etc. Even better it will drive in the right direction without modification and the linkage is a simple single rod that comes forwards making it very very easy to set up. Add in the fact they didn't remove the bell housing in the change from Audi 80 gearbox to Porsche 924/944 and the fact the spline patterns are all easy to find from other manufacturers makes it an ideal box to connect up to your engine via a conversion plate (flat plate drilled for your engine and the gearbox bell housing).
Plus they are very cheap and strong. As said I'm breaking one down for parts and scrap tomorrow, if your tempted £50 and it's yours.
You would of course mount the engine inline as opposed to transverse, ultimately it would give a nice end result. You could of course scrap the whole Peugeot engine and fit the gorgeous Audi 2.3 5pot however it is a heavy engine and the benefit of a straight bolt up to box is outweighed by the weight.
For some reason I assumed you were using the 944 box as well.
You have 2 problems as far as I can see and physically fitting it in is the easy one. Trickier is getting the gear linkage forwards (not hard if cable) and working smoothly.
In your position I would seriously look at going a bit more advanced but also ending up with a far nicer finish.
The Porsche 924/944 box is already designed to work in exactly that configuration it is designed to fit in what is basically a Beetle rear suspension and will of course fit the Porsche hubs/shafts etc. Even better it will drive in the right direction without modification and the linkage is a simple single rod that comes forwards making it very very easy to set up. Add in the fact they didn't remove the bell housing in the change from Audi 80 gearbox to Porsche 924/944 and the fact the spline patterns are all easy to find from other manufacturers makes it an ideal box to connect up to your engine via a conversion plate (flat plate drilled for your engine and the gearbox bell housing).
Plus they are very cheap and strong. As said I'm breaking one down for parts and scrap tomorrow, if your tempted £50 and it's yours.
You would of course mount the engine inline as opposed to transverse, ultimately it would give a nice end result. You could of course scrap the whole Peugeot engine and fit the gorgeous Audi 2.3 5pot however it is a heavy engine and the benefit of a straight bolt up to box is outweighed by the weight.
I love the idea but it would mean cutting a rather big hole into the chassis right where the strength is at the rear bulkhead! I could do this but it would require quite a bit of fabrication to facilitate. I also thought that the Porsche drivetrain utilised a long propshaft from the engine to the rear transaxle that I have no space to fit.
Now I could use the Porsche transaxle and bolt on another engine to it, the Audi 5 pot for example, but then I could just take the whole Audi FWD setup and use it complete, as the engine sits in front of the gearbox mounted transversely.
What I am not sure of is the space required, I have about 47cm between the driveline and the major chassis member. How long are these setups and how much chopping would I have to do?
Every answer sparks more questions!
Now I could use the Porsche transaxle and bolt on another engine to it, the Audi 5 pot for example, but then I could just take the whole Audi FWD setup and use it complete, as the engine sits in front of the gearbox mounted transversely.
What I am not sure of is the space required, I have about 47cm between the driveline and the major chassis member. How long are these setups and how much chopping would I have to do?
Every answer sparks more questions!
I have taken some photos to demonstrate:
Here you can see the basic setup. You can also see the box section that I have added to the chassis to raise the body and provide addition strength. It is overkill I know but I will lose some of the weight by cutting holes into it before I finish.
This shows exactly how tight the space is! The small rod is just resting in the driveline and is, roughly, accurate. From the driveline to the original gearbox mount, the small bracket below the centre of the torsion bar housing, is 35cm and from the driveline to the large box section is 47 cm.
This is a closer look at the same problem. The distance between the A-arm mounts is 31 cm, between the spring plates is 107 cm and the track is 155 cm.
All measurements are approximate and meant to give a sense of scale not for any other purpose!
Here you can see the basic setup. You can also see the box section that I have added to the chassis to raise the body and provide addition strength. It is overkill I know but I will lose some of the weight by cutting holes into it before I finish.
This shows exactly how tight the space is! The small rod is just resting in the driveline and is, roughly, accurate. From the driveline to the original gearbox mount, the small bracket below the centre of the torsion bar housing, is 35cm and from the driveline to the large box section is 47 cm.
This is a closer look at the same problem. The distance between the A-arm mounts is 31 cm, between the spring plates is 107 cm and the track is 155 cm.
All measurements are approximate and meant to give a sense of scale not for any other purpose!
Yes the Porsche system integrates a torque tube, however the actual box will still accept an engine mounted direct (it was adapted to the torque tube system as opposed to a fresh design).
I think the major problem is your chassis, it is designed to take a rear engine, now the same suspension is used on the 924 series but they get around the problem by using a thin torque tube to get past the tight spot of the torsion tube carrier etc.
Is there any reason your trying to get away from the flat 4 engine mounted behind box?
I think the major problem is your chassis, it is designed to take a rear engine, now the same suspension is used on the 924 series but they get around the problem by using a thin torque tube to get past the tight spot of the torsion tube carrier etc.
Is there any reason your trying to get away from the flat 4 engine mounted behind box?
Wildoliver,
You have a lot to answer for! I am now wondering if the Audi 1.8 turbo would fit. It is relatively small, light and compact and comes, in the Audi versions, packaged in a transverse setup. It is also not very expensive and readily available. I am struggling to get the overall dimensions but the limiting factor, as I see it, is getting the engine to fit between the A-arm mounting points. There is also the question of gear linkage but that is a concern with every set up, even the Porsche 044 box as it must be designed to run straight forwards over the prop shaft to the gear lever and I will have an engine in the way! I can cut the torsion bar housing centre out, there are coil over conversions that replace the torsion bar itself and thus the centre is not needed. I would need to keep the mounting points because if I have to cut them off I may as well use the Peugeot setup I have as I will have to manufacture new strut tops and suspension etc.
Is this a daft idea?
You have a lot to answer for! I am now wondering if the Audi 1.8 turbo would fit. It is relatively small, light and compact and comes, in the Audi versions, packaged in a transverse setup. It is also not very expensive and readily available. I am struggling to get the overall dimensions but the limiting factor, as I see it, is getting the engine to fit between the A-arm mounting points. There is also the question of gear linkage but that is a concern with every set up, even the Porsche 044 box as it must be designed to run straight forwards over the prop shaft to the gear lever and I will have an engine in the way! I can cut the torsion bar housing centre out, there are coil over conversions that replace the torsion bar itself and thus the centre is not needed. I would need to keep the mounting points because if I have to cut them off I may as well use the Peugeot setup I have as I will have to manufacture new strut tops and suspension etc.
Is this a daft idea?
wildoliver said:
Yes the Porsche system integrates a torque tube, however the actual box will still accept an engine mounted direct (it was adapted to the torque tube system as opposed to a fresh design).
I think the major problem is your chassis, it is designed to take a rear engine, now the same suspension is used on the 924 series but they get around the problem by using a thin torque tube to get past the tight spot of the torsion tube carrier etc.
Is there any reason your trying to get away from the flat 4 engine mounted behind box?
The main reasons not to use the flat 4 are that it is very expensive to get any power out of and because of it's location detracts from the handling due to the large mass of engine sitting outside the driveline.I think the major problem is your chassis, it is designed to take a rear engine, now the same suspension is used on the 924 series but they get around the problem by using a thin torque tube to get past the tight spot of the torsion tube carrier etc.
Is there any reason your trying to get away from the flat 4 engine mounted behind box?
wildoliver said:
Have you not considered a subaru flat 4? Cheap, strong and not expensive to tune up to silly power. Were it me I would be using a subaru flat 4 with either the strongest VW box available or a Porsche 915 box.
Plus the COG would be far far lower.
When I was looking onto this originally that would have been my plan. The trouble is that a reasonably strong VW gearbox or Porsche one are at least £500, and I mean at least! That blew a big hole in my budget just for the gearbox. The Subaru engines are also not cheap to buy and that also put me off. The Audi 1.8t and box can be got for the same as I would pay for just the gearbox, so it makes economic sense, sort of.Plus the COG would be far far lower.
I usually try to give at least one workable solution to a problem, but I'd say that you're really going to be struggling here.
The main problem is your choice of semi-trailing arms for the rear suspension. These are, as you've found out, quite vertically tall - and get taller when you take suspension travel into account. The lowest possible position of the sump is dictated by the highest position of the semi-trailing arm. This will, however, be far above the static position that your diff will want to be at.
All lower wishbones on front-wheel-drive vehicles are either spaced to go around the sump or are so flat that they are able to live entirely under the sump.
You have correctly identified the solutions. Either;
One. Use a conventional transaxle (such as the Audi) and put the engine on the front of the gearbox. This will be a conventional mid-engined car like, say, GT40
Two. Use a conventional transaxle (such as the Audi) and put the engine in the front - like Porsche 924.
Three. Go rear-engined like Beetle, 911, etc.
Four. Use a front-wheel-drive engine and gearbox assembly, but behind your rear axle line. This gives you the old 5-reverse/1-forward problem. As correctly identified, all engines spin anticlockwise when you're looking at the flywheel APART FROM most Hondas, which spin clockwise. This means that in order to package a Honda engine in front of a front axle, the Honda gearbox must be a complete mirror image of a "normal" one. ( The Rover PG-1 gearbox is almost identically a mirror-image of the corresponding Honda gearbox, for example ). You have two means to achieve this option. Either you could use a "normal" gearbox and mate a Honda (backwards) engine to it OR use a Honda gearbox and mate a "normal" engine to it.
good luck - and keep us updated.
The main problem is your choice of semi-trailing arms for the rear suspension. These are, as you've found out, quite vertically tall - and get taller when you take suspension travel into account. The lowest possible position of the sump is dictated by the highest position of the semi-trailing arm. This will, however, be far above the static position that your diff will want to be at.
All lower wishbones on front-wheel-drive vehicles are either spaced to go around the sump or are so flat that they are able to live entirely under the sump.
You have correctly identified the solutions. Either;
One. Use a conventional transaxle (such as the Audi) and put the engine on the front of the gearbox. This will be a conventional mid-engined car like, say, GT40
Two. Use a conventional transaxle (such as the Audi) and put the engine in the front - like Porsche 924.
Three. Go rear-engined like Beetle, 911, etc.
Four. Use a front-wheel-drive engine and gearbox assembly, but behind your rear axle line. This gives you the old 5-reverse/1-forward problem. As correctly identified, all engines spin anticlockwise when you're looking at the flywheel APART FROM most Hondas, which spin clockwise. This means that in order to package a Honda engine in front of a front axle, the Honda gearbox must be a complete mirror image of a "normal" one. ( The Rover PG-1 gearbox is almost identically a mirror-image of the corresponding Honda gearbox, for example ). You have two means to achieve this option. Either you could use a "normal" gearbox and mate a Honda (backwards) engine to it OR use a Honda gearbox and mate a "normal" engine to it.
good luck - and keep us updated.
I've actually come up with a quite simple and elegant solution to your problem, but it will be a bit of re-engineering and will take your budget over your planned limit.
I understand why your wanting to go Mid or Rear engined as the front of the car is quite sloped, however as we can all see your really struggling to package it, as above really with the rear set up you currently have you only really have 2 options, go rear engined, or use the Porsche transaxle/torque tube and a front engine.
The problem with going rear engined is that unless you have a big engineering budget (I.E. Porsche) it is never going to handle well. Also it may sit too far back, your going to have to use a weak OR expensive box.
The problem with going front engined is getting an engine in to the sloping front. However your back end and gear linkage problems instantly dissapear, the Porsche TT fits straight over that rear suspension carrier (as it is designed to) the gearbox is easy to mount up to the frame and the gear linkage is all pre packaged and thus is a really simple job.
However the only engine that would work is a subaru flat 4. Nice low COG, good power to weight/size and easy to get hold of (so reasonably cheap). The good news is it will fit on to the torque tube very very easily as the TT has a flat mounting flange. This is the route I would take, plus you have the benefit of a solid spine running the length of the car to use as a stressed member or just to hang things like exhaust off.
IMO it is the only way to go unless you do a redesign on the rear end.
I understand why your wanting to go Mid or Rear engined as the front of the car is quite sloped, however as we can all see your really struggling to package it, as above really with the rear set up you currently have you only really have 2 options, go rear engined, or use the Porsche transaxle/torque tube and a front engine.
The problem with going rear engined is that unless you have a big engineering budget (I.E. Porsche) it is never going to handle well. Also it may sit too far back, your going to have to use a weak OR expensive box.
The problem with going front engined is getting an engine in to the sloping front. However your back end and gear linkage problems instantly dissapear, the Porsche TT fits straight over that rear suspension carrier (as it is designed to) the gearbox is easy to mount up to the frame and the gear linkage is all pre packaged and thus is a really simple job.
However the only engine that would work is a subaru flat 4. Nice low COG, good power to weight/size and easy to get hold of (so reasonably cheap). The good news is it will fit on to the torque tube very very easily as the TT has a flat mounting flange. This is the route I would take, plus you have the benefit of a solid spine running the length of the car to use as a stressed member or just to hang things like exhaust off.
IMO it is the only way to go unless you do a redesign on the rear end.
The only problem with going front engined, with a Subaru or other engine, is that there is nowhere for the torque tube to run! The centre tunnel is actually a closed member and running the torque tube down it would be quite difficult. I could get a Ford based chassis for the Eagle, they used the Cortina running gear, but that would still need a good deal of changes and, perhaps more importantly, I don't have one!
I have made a number of changes to the original layout, the major one being the addition of the 40mm x 80mm section box section around the original body / chassis mounting points. This has had the dual effects of strengthening the chassis and raising the body. My current plan is to actually cut into the main chassis and truly mid-mount an engine driving the back wheels. I will either use the Porsche transaxle and my Peugeot engine or, cost and availability dependant, utilise a complete Audi engine and box. The rear cross member will be redesigned to run flat across the car and carry the ends of the torsion tubes. This will allow me to cut the centre section out but will necessitate the fitting of coil overs to replace the torsion springs. The box section will turn through 90 degrees and protrude into the cabin, to allow the engine to sit longitudinally in front of the axle, and I will adapt the rear bulkhead to accommodate this. The car only seats two so space is not a major problem. The 40 x 80 box is strong enough to carry the suspension arms and replace the strength lost by cutting the rear of the chassis spine. I will weld the box section into the chassis where it crosses and there will have to be a cradle made to support the engine.
This is the plan and I will update as I get on with it!
I have made a number of changes to the original layout, the major one being the addition of the 40mm x 80mm section box section around the original body / chassis mounting points. This has had the dual effects of strengthening the chassis and raising the body. My current plan is to actually cut into the main chassis and truly mid-mount an engine driving the back wheels. I will either use the Porsche transaxle and my Peugeot engine or, cost and availability dependant, utilise a complete Audi engine and box. The rear cross member will be redesigned to run flat across the car and carry the ends of the torsion tubes. This will allow me to cut the centre section out but will necessitate the fitting of coil overs to replace the torsion springs. The box section will turn through 90 degrees and protrude into the cabin, to allow the engine to sit longitudinally in front of the axle, and I will adapt the rear bulkhead to accommodate this. The car only seats two so space is not a major problem. The 40 x 80 box is strong enough to carry the suspension arms and replace the strength lost by cutting the rear of the chassis spine. I will weld the box section into the chassis where it crosses and there will have to be a cradle made to support the engine.
This is the plan and I will update as I get on with it!
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