Discussion
Hi,
My diff is making noises now on both over run and acceleration, so I think its time for a new one. Rather than replace I would like to upgrade. I understand that a LSD is the way forward.
What type is best? Plate ones or the other type.
The car is a Fisher Fury with an 1800 zetec engine, full screen and a large driver.(so its quite heavy)
The rear axle is an English axle.
The car is mainly driven on the road. but once all is sorted I would like to track it 4 or 5 times a year.
Thanks
My diff is making noises now on both over run and acceleration, so I think its time for a new one. Rather than replace I would like to upgrade. I understand that a LSD is the way forward.
What type is best? Plate ones or the other type.
The car is a Fisher Fury with an 1800 zetec engine, full screen and a large driver.(so its quite heavy)
The rear axle is an English axle.
The car is mainly driven on the road. but once all is sorted I would like to track it 4 or 5 times a year.
Thanks
The noises you describe are almost certainly not the 'diff', strictly speaking. They're more likely to be due to either the bearings or the crown wheel and pinion being shot. Both of these form part of the diferential/final drive assembly in the midle of your axle, but are not amongst the parts that would be supplied if you bought an LSD from Quaife or whoever.
Which means that you can fix the problem without spending on a new diff or (conversely) if you do buy a new LSD, you'll still need to buy new CWP/bearings as well if you want to fix the problem.
...and personally, I wouldn't be worrying about a LSD for road and occasional track use. You don't really need one on a 'Seven' type car.
Which means that you can fix the problem without spending on a new diff or (conversely) if you do buy a new LSD, you'll still need to buy new CWP/bearings as well if you want to fix the problem.
...and personally, I wouldn't be worrying about a LSD for road and occasional track use. You don't really need one on a 'Seven' type car.
Hi Dave, having had a Fury / Phoenix with and without an LSD i would definately have an LSD, if for no other reason than mm perfect donuts and 50yd powerslides. But i forgot, you got to experience that in France with us didn't you!!! My XR4x4 is quite aggressive, but you cannot go far wrong with a Quaife ATB in a Fury. I'd just bite the bullet and get them to build it for you with all new bearings ect. Under normal driving I think with an ATB it is not too intrusive with causing understeer, mine you can feel the effects dynamically.
pigeondave said:
Is there a book/web guide on how to do it?
There's quite a good, detailed description in the Lotus Elan Factory Workshop Manual (the Elan uses the English CWP/diff in a Lotus casting), but TBH if you're not sure what you're doing it'll mainly serve to scare you into giving the job to a specialist. If you want a pdf copy of the appropriate section from the manual, mail me via my profile and I'll send you one (though it might take me a day or two to get round to it).
With a mechanic mate of mine, we set up an LSD in my 7 replica. Unfortunately, I can't remember exactly what we did for the backlash (it involved feeler gauges, but not which one), but I was told that if it whines when accelerating, then it's too far one way; if it's making too much noise when decelerating, then it's too far the other way.
Of course, using noise is a bit hit and miss, and you'd need to take it apart each time to change.
Don't forget to put oil in it!
Unlike our first attempt to change the diff (luckily not an LSD one) - I was asked if there was oil in it, I thought he meant /any/ oil, rather than /enough/ oil, so I said "yes". It lasted 250 miles...
Of course, using noise is a bit hit and miss, and you'd need to take it apart each time to change.
Don't forget to put oil in it!
Unlike our first attempt to change the diff (luckily not an LSD one) - I was asked if there was oil in it, I thought he meant /any/ oil, rather than /enough/ oil, so I said "yes". It lasted 250 miles...
tribbles said:
...if it whines when accelerating, then it's too far one way; if it's making too much noise when decelerating, then it's too far the other way.
Of course, using noise is a bit hit and miss, and you'd need to take it apart each time to change.
You can check the mesh before putting everything back together by using engineer's blue on the crownwheel teeth, then rotating the pinion both ways to see what the contact area is. Basically, the pinion needs to be meshing centrally on the face of each tooth on the crownwheel.Of course, using noise is a bit hit and miss, and you'd need to take it apart each time to change.
I've got a mate who works for a gearbox company, so I've never done one myself, but when I've seen him do it he's always used a dial gauge for measuring the backlash (although it's pretty much redundant as he is experienced enough to do it by 'feel' most of the time).
(edited for crap typing)
Edited by Sam_68 on Monday 6th July 23:30
Sam_68 said:
I've got a mate who works for a gearbox company, so I've never done one myself, but when I've seen him do it he's always used a dial gauge for measuring the backlash (although it's pretty much redundance as he is experienced enough to do it by 'feel' most of the time).
Now you mention it, he did use a dial gauge for it. But ISTR we couldn't work out exactly how you were supposed to use it (i.e. at which point do you measure it from).In any case, it worked fine, and was a lovely drive (and doing doughnuts [properly] in the carpark was fun).
Rebuilding CWP asemblies is most definitely not a job to be undertaken lightly,particularly as you have no experience or knowledge of the basics.
OK its not "rocket science" but obtaining the correct bedding patterns is often a very time consuming job especially as you don't have any setting jigs to use as a starting point.
Sams tip of using engineers blue is the way to do it,when I was building them in industry 35 years ago we used a thin paste called "Red Raddle",originally ,I believe ,used for marking sheep!! This is almost certainly incredibly illegal to use nowadays as the mixture consisted of castor oil,EP 90 and red lead powder! The subtle feathering it gave made setting the CWP assemblies up precisely far easier than with blue,in your case though I would think you are going to have a real struggle to get the correct bedding without gauges,shims etc;
I hope this doesn't appear too negative,I'm all for having a go ,particularly if funds are short but in this case the potential for disaster is great.At the very least if you are prepared to try,get someone who knows about gears to take a look at the tooth faces just to ensure the case hardening is not breaking up and that running the gears out of alignment hasn't scuffed/knackered them because if they are U/S no one will never be able to get them set correctly.
Personally,if funds are short I would advise paying someone with the correct kit and experience to set the CWP up correctly instead of spending the money on fitting a LSD into a badly set up axle.
Just had another thought,if its noisy both under load and on the overrun
its probably only the pinion bearings that have failed,assuming that no shrapnel has damaged the crown wheel bearings you may be able to get away with just fitting new pinion bearings,this would probably mean virtually no change to the settings as the taper roller bearings will be made to very tight tolerances,so replacing them will(hopefully) not alter the current settings,if a collapsible spacer is used to set the drive flange nut torque,a new one of those will probably be required,as will a new oilseal on the pinion nose.
OK its not "rocket science" but obtaining the correct bedding patterns is often a very time consuming job especially as you don't have any setting jigs to use as a starting point.
Sams tip of using engineers blue is the way to do it,when I was building them in industry 35 years ago we used a thin paste called "Red Raddle",originally ,I believe ,used for marking sheep!! This is almost certainly incredibly illegal to use nowadays as the mixture consisted of castor oil,EP 90 and red lead powder! The subtle feathering it gave made setting the CWP assemblies up precisely far easier than with blue,in your case though I would think you are going to have a real struggle to get the correct bedding without gauges,shims etc;
I hope this doesn't appear too negative,I'm all for having a go ,particularly if funds are short but in this case the potential for disaster is great.At the very least if you are prepared to try,get someone who knows about gears to take a look at the tooth faces just to ensure the case hardening is not breaking up and that running the gears out of alignment hasn't scuffed/knackered them because if they are U/S no one will never be able to get them set correctly.
Personally,if funds are short I would advise paying someone with the correct kit and experience to set the CWP up correctly instead of spending the money on fitting a LSD into a badly set up axle.
Just had another thought,if its noisy both under load and on the overrun
its probably only the pinion bearings that have failed,assuming that no shrapnel has damaged the crown wheel bearings you may be able to get away with just fitting new pinion bearings,this would probably mean virtually no change to the settings as the taper roller bearings will be made to very tight tolerances,so replacing them will(hopefully) not alter the current settings,if a collapsible spacer is used to set the drive flange nut torque,a new one of those will probably be required,as will a new oilseal on the pinion nose.
Edited by Auntieroll on Monday 6th July 20:04
On a slightly lighter note... I remember an anecdote about some fella by the name of Chapman who took a completely mismatched crownwheel and pinion and made them talk to each other by running them in metal polish instead of oil for a few hundred miles. Didn't do his reputation as a car builder any harm, as I recall, so it can't be such an exact science. 
Not sure I'd want to try it with several hundred quid's worth of shiny new LSD, though.
Not sure I'd want to try it with several hundred quid's worth of shiny new LSD, though.
[quote=Sam_68]On a slightly lighter note... I remember an anecdote about some fella by the name of Chapman who took a completely mismatched crownwheel and pinion and made them talk to each other by running them in metal polish instead of oil for a few hundred miles. /quote]
Shiny!
Shiny!
Edited by eddie1980 on Tuesday 7th July 12:42
I agree with SAM68 re BGH,great company in my experience.
WRT setting up being such an exact science,if you want a long lasting,quiet,reliable diff assembly then doing it correctly is vitally important.
Try driving any distance with a noisy diff only 6" from your left shoulder,that should change your mind fairly quickly!!
WRT setting up being such an exact science,if you want a long lasting,quiet,reliable diff assembly then doing it correctly is vitally important.
Try driving any distance with a noisy diff only 6" from your left shoulder,that should change your mind fairly quickly!!
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