Replacing the Differential Questions

[rtg]

I'm changing my standard Diff in the S3 for a LSD unit. While I'm at it I need to replace a torn gaiter on the inner CJ joint.

So, with the car jacked up how easy is this to do with the body on? I've rebuilt the car with body off, and was obviously was a lot easier then, although I probably got carried away with the greasing and thus burst the gaiter.

If the gaiter has torn, should I just replace the rubber gaiter or go and replace all 4 CJ joints? Are all 4 CJ joints identical?
The car's done 105K miles. From memory I thought they were all identical.

Does anyone have a part code for the torx bolts holding the CJ joints into the diff?

Finally - the LSD was from a low mileage Granada (apparently 70K miles), so was just planning to take the back off and replace the oil. Is there anything else I should check/service while I've got the Diff on the bench?

Cheers, Richard.

[GreenV8S]

Split boots are available but seem like a waste of time to me, so you'll need to take one CV off to replace the damaged boot. It makes sense for that to be the inner one since you are taking the diff out.

Personally I wouldn't bother replacing any CVs unless they were noticeably worn or damaged. If one is worn its pair will probably be worn too since they do equal work, so I'd replace them as a pair.

The bolts would be 12.9 grade 8mm x 50mm; the originals would have had a Torx45 cap head.

If the diff has excessive play, it would be worth getting it rebuilt while it is out.

Edited by GreenV8S on Monday 13th May 23:06

[rtg]

Ok - many thanks. There's no play in the diff, but it feels stiff. I don't know if this is just normal but I'm sure it's harder to rotate the proshaft end than a non-LSD version.

[phillpot]

rtg said:

So, with the car jacked up how easy is this to do with the body on?

It's a bit of a fiddle, but doable. I think you may have to drop the rear mount with the diff, no room to get the two big bolts out?

Is the rear mount okay, some nice, if pricey, silicone ones are available.

Here are your bolts, same company can also supply gaiters and very reasonably priced cv joints if you do require any.

I'm told MOT examiners can "be funny" about plastic tie wraps on cv gaiters, should be metal

There was a guy doing these in stainless but can't find the ad. now? Think he may have used a weird description so not easy to search..... or he don't do 'em anymore!

They are possibly not "the best" cv joints but myself, and I believe a few others, have found them quite adequate for our little S's, if I had a 300 plus BHP supercharged beastie I might go shopping for some other brand.

As Peter says, if yours are in good order and possible OEM I'd leave well alone.

ETA... have a search through some old posts, loads of useful advice and suggestions are out there

Edited by phillpot on Tuesday 14th May 20:09

[Maffe]

It can be done with the body on, my father and I did that last year when fixing my s3 before the Monaco eurotour.
Good to be to persons since it was little fiddly, definitely helps if you take the fuel tank out and when your at it give the tank And bracket some love
Ended up replacing the old ford diffmount with something like the one phillpot linked to.

Hard to realise that it was a year ago since we drow to Monaco and all preparations before the trip!
https://www.pistonheads.com/gassing/topic.asp?h=0&...

[v8s4me]

The Torx bolts can be a right bstard to get out so invest in a very good quality hardened steel Torx bit and a man-sized impact driver.

Top-tip, don't buy a new Brittletool Torx bit...


As a last resort, be prepared to cut the heads off.

GreenV8S said:

.....The bolts would be 12.9 grade 8mm x 50mm; the originals would have had a Torx45 cap head....

Mine are T40.

Edited by v8s4me on Tuesday 14th May 21:30

[phillpot]

v8s4me said:

Top-tip, don't buy a new Britool Torx bit...

you didn't, you borrowed mine

[GreenV8S]

v8s4me said:

Mine are T40.

You could well be right. My notes show T45 but it has been a few years since I had one in my hand. If you get the diameter, length and thread are right there probably won't be any choice about the bit size, just Torx versus hex.

[rtg]

Thanks all - Yep I've invested in multiple chocolate T45 tools and hence the need for new bolts. Was nice when I splashed out on a proper tool and the rest of the bolts came straight out. PhillPot - thanks for the info and links - will follow up.

Edited by rtg on Tuesday 14th May 22:11

[v8s4me]

phillpot said:

v8s4me said:

..Top-tip, don't buy a new Britool Torx bit...

you didn't, you borrowed mine

True, but I broke yours and then had to buy you a new one

[greymrj]

Yes you can get the diff off, no need to take off anything not attached except the exhaust. But the front right bolt (if I remember correctly) is VERY difficult, there isnt enough room to withdraw it. I needed a crow bar to get the last mm of clearance and I took a tiny bit off the bolt before replacing it. The diff is pretty heavy and I doubt you will be able to hold it and fit bolts at the same time. I used a length of plank and some blocks to slide it back into approx position.

That diff mounting rubber block is a problem. No supply at present. The fancy racing ones are good but expensive. I was lucky enough to get hold of a very good second hand one.

Happy with those joints but not a fan of the Torx bolts they supply. They are really designed for machine fitting. Easy to damage. This has been discussed before and alternative Hex socket heads from Unbrako are a better bet. Quite a few cars have had bolts come loose and it is a bugger to re-tighten on the roadside using a torx while a GOOD hex key and a short pipe is far easier. A couple of people have gone to the trouble of cobalt drilling and wiring the bolts. I have paint marked mine and check them quite regularly.

[sebackman]

If your are changing the entire diff please check the new diff casing in advance. The Granada/Scorpio/Sierra from later cars, often with LSD, did have an reinforced case that is too wide to go in.

I mounted an LSD unit in the original diff years ago but wanted to get a bit lower gearing so I found a 4,27 diff from a Granada and swapped over my LSD unit. It did not fit. I took many hours to figure out that it is indeed wider on top. I took out the grinder and just cut away some of the case reinforcements. Please see pictures.

kind regards
//Rob

[rtg]

Cheers Rob - I'll bear that in mind when the diff comes out.