Area Representative Richard Price Posted October 25, 2001 Area Representative Share Posted October 25, 2001 I am considering fitting a Quaife ATB LSD and perhaps a change of final drive ratio as a retro fit and would like to carry out all of the work myself. However, the Haynes manual for the Sierra diff. Says:- "Overhaul of the final drive unit requires the use of several special tools and fixtures that are not normally available to the home mechanic" Not very helpful ! I may be able to put my hands on (or even make) suitable tools, if I knew what was required. What tools are required and what is the procedure to rebuild the diff. unit? Link to comment Share on other sites More sharing options...
oilyhands Posted October 25, 2001 Share Posted October 25, 2001 I've stripped and built one with no special tools, but it's a lot easier with the right tools to undo the castellated bearing retainers and to hold the prop flange while undoing the retaining nut. You will need a set of torq bits to undo most of the fasteners both inside and out. If the diff is the Lowbro type you have to remove the backplate and then the output shaft retaining circlips which are right in the centre of the diff, once the circlips are off the output shafts / drive flanges can be removed. After this the locking plates from the bearing retainers can be removed and the retainers can then be unscrewed and removed. The input/prop flange also has to be removed and you may need a puller to get this off. It should then be possible to manhandle the diff assembly out of the casing once the bearings have been removed from the outside of the diff unit. It was 5 years ago I last did one so there may be the odd detail missing... Oily Edited by - oilyhands on 25 Oct 2001 14:40:37 Link to comment Share on other sites More sharing options...
J.R. Posted October 25, 2001 Share Posted October 25, 2001 Ditto what oilyhands said, also remember a big hammer & chisel (essential for all transmission work) you probably wont need it until you come to refit the quaife ATB / CWP assembly wherupon you find it wont go through the casing as the Ford unit came out Link to comment Share on other sites More sharing options...
sjwb Posted October 25, 2001 Share Posted October 25, 2001 This site frightens the crap out of me! No tools, want to do it myself? You are joking - right? However you were right to ask Richard! To change the gear-set you need to set the pinion height to plus or minus 0,0005" of a figure you will never learn and for this you need a parallel of the correct diameter, a dummy pinion (optional) and a set of slip gauges. Now you need to regulate the pinion pre-load. Depending on the type of bearing set, this may be a crush washer or shims; either way, special tools are required to hold the pinion flange and measure the rotational torque. Not to mention of course getting the bearings on and off whilst using the handling procedures that experience and training impart. On to the difficult bit. It is also the following that will apply if you are just fitting an LSD and not the complete gear-set. To set the crown wheel relative to the pinion (having got the depth of engagement correct) we need to adjust the backlash and diff box bearing preload. This is the skillful bit - believe me. A) Because there is always run out on the diff box to confuse the issue (crown wheel mounting face). B) The bearing preload adjustment has a profound affect on the backlash and so it becomes a juggling act. To judge the attained preload by observed turning torque is difficult enough and to assess it as a combination of the two (torques) is nigh on impossible. Experience and or tooling again. Get it wrong (as you surely will) and at best you will have a noisy diff. At the worst? A seized unit which hopefully won't wreck the car. This is not meant to demean, or imply stupidity, merely to point out that there are some skills that are very special and cannot be learned on a one-off basis. The very act of training in cases like this usually means that the trainer might just as well have done the job in the first place. In closing, please think again when giving advice that may send others on a (sic) road to ruin. Steve B Link to comment Share on other sites More sharing options...
Norman Tebbit Posted October 25, 2001 Share Posted October 25, 2001 Sounds like a piece of pi*s. Everyone knows theres only two torque settings - tight.... & F***ing tight. wink.gif before anyone takes offence Link to comment Share on other sites More sharing options...
Fast Westie Posted October 26, 2001 Share Posted October 26, 2001 Richard The other tool you can use is a car boot to take the lot to Phil Stewart at Road and Race Transmissions 01959 525105 I gave up doing it myself after two chewed up CWP sets The car in front is a Westfie1d wink.gif Link to comment Share on other sites More sharing options...
Nick M Posted October 26, 2001 Share Posted October 26, 2001 I spoke to Phil at Road and Race and he reckoned on about £75 to take the internals of a 3.62 LSD, swap the CWP and then rebuild it into the casing. Sounds like a bargain to me - I'll be taking mine there in about a two weeks to get this done. Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted October 26, 2001 Share Posted October 26, 2001 Mr N Tebbit. That's the trouble with you non-technical types.Always over tighten things! The only torque setting to remember is this one:- "Up to shear; then back half a turn"! Say this to someone who THINKS he/she knows what's going on & you can soon see if they are switched on or not. Phil Stewart (Road & Race Transmissions) would be worth the trip 'cos I have seen Keith (his colleague) at work and they remove some of the internal casing material so as to get the unit in with the bearings on. Some Co's fit the bearings once the LSD is in the case and that means you have to remove/destroy them in the casing itself if it ever has to come apart again. Not clever! Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted October 27, 2001 Author Area Representative Share Posted October 27, 2001 Gentlemen, Thanks for the advice, but I reiterate that I would like to do the job myself, and whilst I am not a motor mechanic, I do work in an engineering environment and understand the need to work to close tolerances and am not frightened by any thing I've heard so far. What I do need is detailed instruction on the required procedure and as I stated originally, the Haynes manual offers no such help. Where can I find this procedure? Link to comment Share on other sites More sharing options...
oilyhands Posted October 27, 2001 Share Posted October 27, 2001 Whereas I'm sure that somewhere such detailed instruction exist, I have the Sierra and Sierra Cosworth official workshop manuals, and they contain no more information than the Haynes manual, there is complete information on rebuilding the gearbox and on replacing the oil seals on the diff, other than that.. nowt. Oily Link to comment Share on other sites More sharing options...
Swiss_Tony Posted October 27, 2001 Share Posted October 27, 2001 Is the Caterham diff the 7" type? James Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted October 28, 2001 Author Area Representative Share Posted October 28, 2001 James, Yes, it's the standard Dedion diff. Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted October 28, 2001 Author Area Representative Share Posted October 28, 2001 James, Yes, it's the standard Dedion diff. Link to comment Share on other sites More sharing options...
Richard Ince Posted October 28, 2001 Share Posted October 28, 2001 Not being technical I have little to add on this subject. However Steve B raises the importance of the pre-load. I struggled for many months with a car that kept understeering. The cause was finally traced to the diff pre-load. To solve this metal was shaved off on a lathe with the result that the car lost it's understeer. £75 paid to the experts at Road and Race looks good value! Link to comment Share on other sites More sharing options...
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