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Building one good diff out of two.

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right finally rejoined, now i can annoy folk on here instead of facebook again!


1971 gt6 mk2 rotoflex with rover V8 and 5 speed box

- weak link is the diff. trying to avoid putting the subaru one in that is sat on garage shelf.


So as some of you know I ejected the rear of my diff out the back of the car a while ago, got a temporary diff and now finally took that out to begin (some kind) of rebuild. Both are now stripped on the bench leaving just the pinion in each.


What I have:

- my 'original' 3.89 ratio GT6 six bolt housed diff with front large castle nut - so I have a solid spacer.

- It has large carrier bearings and a very nice tight but smooth differential in it with copper shims

- the rear housing as said was shattered by a pinion tooth wedging under crown wheel -  so I have another 6 bolt tail I will use.

- My pinion has lost one of its baby teeth but the CW looks okay.

- This diff WAS nice and quiet.


The temporary diff

- is the holy grail 3.63 but with a spitfire front bracket, 4 bolt rear case, and a shallower nylock front nut - so it should be a collapse spacer.

- it has smaller carrier bearings and the differential is sloppy with approx 0.8mm of play moving a single gear in/out

- The crown wheel has a bit of burring at the edge of the troughs of about 7 teeth and a scored line on the edge of the wheel (not the teeth) of     the same number of teeth.

- This diff whines on load of acceleration or deceleration.



Any advice at this point is appreciated.

I cant afford to get the diff sorted by someone brilliant so as neither owes me anything I wish to try myself to make a tough (as possible diff with what I have.


This is what I think i should do:


1. use my GT6 front housing

2. use my spare 6 bolt rear case (tapped for a drain plug)

3. use the 3.63 CWP matched set (even thought potentially still noisy)

4. use my solid spacer (doing all the difficult pre-load and shimming i know will need doing)

**** Can you use a solid spacer on a pinion that uses a collapse spacer?? ****

5. Use my gt6 carrier with the larger bearings

6. replace all seals and bearings.




1. will the solid spacer go on the pinion off the other diff? (solid is a stronger)

2. are the output shafts stronger on the gt6 diff? (the shafts look the same but the spitty one has sealed bearings)

3. I'd read that the later (TR7 4 speed) carriers were stronger, but are they stronger than my gt6 one?



Thank you everyone :-)

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