What Engine for 500BHP
Discussion
I knew it would brake, but didnt expect it so soon, especially with a brand new box - I have a used box, or two, so will be fitting one of those to see what happens....
It broke in 4th gear going on the A1 outer lane cleared and I floored it at around 2500 rpm then bang grind crunch, I guess it went when the turbo came in....
It is possible to get gear sets, I believe Bacci do a full box set for for around Eur 5000, but that is a dog set & I also think Avanti do them as well.....
It broke in 4th gear going on the A1 outer lane cleared and I floored it at around 2500 rpm then bang grind crunch, I guess it went when the turbo came in....
It is possible to get gear sets, I believe Bacci do a full box set for for around Eur 5000, but that is a dog set & I also think Avanti do them as well.....
Just remembered a twin turbo 3.7 bored Alfa V6 powered Ultima. I believe it was in South Africa but I'm sure you could ask for one over here. 
It could be a case of wear and extra tear rather than a stress failure.
In the mean time here's a nice six speed...
http://www.ebay.co.uk/itm/Alfa-Romeo-156-V6-6-Spee...
...for £200
It could be a case of wear and extra tear rather than a stress failure.
In the mean time here's a nice six speed...
http://www.ebay.co.uk/itm/Alfa-Romeo-156-V6-6-Spee...
...for £200
Brand new gear boxes can be more fragile than s/h ones because the parts have not:
1) been repeatidly stress cycled (and hence stress relieved by those cycles)
2) the surface finish in the mesh zone is generally not optimal as the gears haven't run together yet
However, if you have just competely ripped the teeth off the gear then it's unlikely to be easily solved without resort to a better material grade for those gears. Also, depending on the layout of the box, shaft seperation and hence poor tooth mating (point loads) can develop in higher gears as the low gears are usually at the "stiffess" end of the shafts. It still seems unlikely that "pure torque" broke 4th gear so soon however (i.e. no shock load, or other transient loading event) I wonder if the 4th gear cluster actually had a machining defect or similar? (might be present on "all" 4th gears pairs, but generally survives the std engines output).
1) been repeatidly stress cycled (and hence stress relieved by those cycles)
2) the surface finish in the mesh zone is generally not optimal as the gears haven't run together yet
However, if you have just competely ripped the teeth off the gear then it's unlikely to be easily solved without resort to a better material grade for those gears. Also, depending on the layout of the box, shaft seperation and hence poor tooth mating (point loads) can develop in higher gears as the low gears are usually at the "stiffess" end of the shafts. It still seems unlikely that "pure torque" broke 4th gear so soon however (i.e. no shock load, or other transient loading event) I wonder if the 4th gear cluster actually had a machining defect or similar? (might be present on "all" 4th gears pairs, but generally survives the std engines output).
Box now stripped....
Point taken re the new box, maybe it was a case of too much too soon, anyways one of my boxes is already stripped and was in good condition, so i will rebuild that one into the new casings after a good clean up and see how that one goes.
Other wise I think a set of straight cut gears will be the order of the day! unless those lotto numbers come up!
Point taken re the new box, maybe it was a case of too much too soon, anyways one of my boxes is already stripped and was in good condition, so i will rebuild that one into the new casings after a good clean up and see how that one goes.
Other wise I think a set of straight cut gears will be the order of the day! unless those lotto numbers come up!
That looks like a nice clean and even strip of cogs there. Very well balanced engine and good reactions by the driver. A lesser driver or poorly built engine would have bent a shaft and fannied the whole lot.
My thinking with the six speed was the difference in ratios would be less so each gear wouldn't need to work as hard but rebuild with the bits you have saves time and faffing about.
Don't forget to put the stripped gears on a chain and wear them around your neck to warn off others.
My thinking with the six speed was the difference in ratios would be less so each gear wouldn't need to work as hard but rebuild with the bits you have saves time and faffing about.
Don't forget to put the stripped gears on a chain and wear them around your neck to warn off others.
Liquid Knight said:
That looks like a nice clean and even strip of cogs there. Very well balanced engine and good reactions by the driver. A lesser driver or poorly built engine would have bent a shaft and fannied the whole lot.
My thinking with the six speed was the difference in ratios would be less so each gear wouldn't need to work as hard but rebuild with the bits you have saves time and faffing about.
Don't forget to put the stripped gears on a chain and wear them around your neck to warn off others.
I had a six speed box to use, but got warned away from them, as they are weaker! The plan is just to swap out the internals as is to get the car on the road again, while i save for some straight cut gears! My thinking with the six speed was the difference in ratios would be less so each gear wouldn't need to work as hard but rebuild with the bits you have saves time and faffing about.
Don't forget to put the stripped gears on a chain and wear them around your neck to warn off others.
Liquid Knight said:
That looks like a nice clean and even strip of cogs there. Very well balanced engine and good reactions by the driver. A lesser driver or poorly built engine would have bent a shaft and fannied the whole lot.
er, what? (you do realise that gearboxes are "constant mesh" don't you???
Max_Torque said:
Liquid Knight said:
That looks like a nice clean and even strip of cogs there. Very well balanced engine and good reactions by the driver. A lesser driver or poorly built engine would have bent a shaft and fannied the whole lot.
er, what? (you do realise that gearboxes are "constant mesh" don't you???Well I Got the box rebuilt today and it wouldn't turn - ho hum... so its stripped again, looks like the bearing on the end of the transmission shaft is touching the diff crown wheel.. tomorrow i will try the diff bearing pre-load shim on the other (wrong) side of the diff, this will move the diff the right way a couple of mm - hopefully it wont move the diff too far so as the gear fouls on the casing instead......
I Noticed another fault with the box, apart from it being full of shreaded gear teeth, the holes that locate the bearings (next to fifth gear) have turned oval which would allow the shafts to spread slightly..... and it was a new casing. my old casings are better, so a bit of mix and match with the casings....
I Noticed another fault with the box, apart from it being full of shreaded gear teeth, the holes that locate the bearings (next to fifth gear) have turned oval which would allow the shafts to spread slightly..... and it was a new casing. my old casings are better, so a bit of mix and match with the casings....
Sorry, I'm a bit late on this one, but it looks like you've spotted the problem with these 'boxes, it's not so much the gears and shafts that are weak, but the casings. The holes holding the bearings on the two main shafts go oval allowing them to spread. The gear teeth lose their mesh and ping off pretty quick.
I've had spectacle plates produced for this problem and an upper plate too to avoid your next issue - the diff and casing breaking whilst being pushed out of the way by the torque.
A pic of the spectacle plate being made alongside the 'box casing being machined at the same time:
You'll just keep on destroying gears until you strengthen the casings.
What clutch are you using btw?
I've had spectacle plates produced for this problem and an upper plate too to avoid your next issue - the diff and casing breaking whilst being pushed out of the way by the torque.
A pic of the spectacle plate being made alongside the 'box casing being machined at the same time:
You'll just keep on destroying gears until you strengthen the casings.
What clutch are you using btw?
stevieturbo said:
ivanhoew said:
how about ,as a bit of a digressive thinking thingy ,a escort cosworth box .
An Escos is an inline box with a separate transfer box and is a s
te gearbox to start with.Perhaps the most unsuitable option possible.
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