Diff Rebuild

[STEVE GILBERT]

I am looking at the pukka Ford Workshop manual for rebuilding Sierra Diffs, I need to remove the main Diff and Crownwheel to install my new LSD and frankly it doesnt look that difficult with few special tools required(puller, press etc) and a dial guage to set the backlash. Romoving the pinion is a no-no but I dont need to do this. My question is has anyone else done this and how did you get on?

I think you could even do it in the car with the tube out the way.

 

Someone must be as daft as me.

 

 

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[Tony Martyr]

I have never seen a book for the Ford diff but used to watch them being stripped, modified and rebuilt when I worked at Ricardo MTC in a workshop with all the correct tools. It is not a suck it and see job because you have to set the meshes cold and exactly otherwise you get noise or / and wear and lots of energy wasted. Also you will want to get it right first time. I would not consider doing it in situ.

Having said that if you drive up the Ghats from Mumbai in India there are on various hair-pin bends a series of Diff-Wallas who will leap out and rebuilt smashed diffs by the road-side in about an hour so it is possible.

[STEVE GILBERT]

3rd world maintenance! thats me!

If anyone wants a copy of the sections from the Ford Manual (and has the correct permissions) mail me and I will do it for £5 to NTL

 

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[sjwb]

Steve,

I wrote this some time ago. I appreciate that the first part is not relevant (assuming all is well in the unit) and I am not undermining any skills tha you may have. But do be careful.

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.

 

Steve B

 

Edited by - sjwb on 22 Oct 2002 22:37:02

[STEVE GILBERT]

Steve B

Given the current silent operation of the unit and assuming I can accurately measure the current average Crownwheel backlash with a Dial-Gauge at the stated 3 triangulated points, after installing the new Diff it seems to me I need then adjust the side to side position/preload as described in the Ford manual through a process of trial and error until I arrive at my average figure of previously measured backlash(assuming it is within the ford specification) or am I missing something?

 

I hope to refit the Taper bearings to the diff if I can recover them from the std unit OK but may have to replace, did you get these off OK?

If you have built one of these up, where did you get the Diff taper bearings/Housings(sold as unit)? Ford want silly money so suspect with a 5 digit type part no someone like Wyko may supply, any thoughts?

 

All advice welcome

 

 

See My Zetec Power 7 Here

[sjwb]

Steve,

Firstly, don't ever re-use bearings. Try a company like Bearing Services Ltd and quote them the number off the bearing race and only use top quality parts. It is absolutely critical that the cones are fitted hard against their abutment

Rotate the CW gear until you find the least backlash and use this position to set the backlash from. Too little, or no backlash will kill the gears. To set the preload you can try the torque method, after having acertained the torque required to rotate the pinion (continuous rotation not that which is required to start it); the best of luck .

 

Steve B