chris walrod

Paul, sent ya a PM

JasonAndreas

The LSD is covered in the 964 workshop manuals.

Jeff96-993

Paul, please write this up as a full DIY, since I have to do it shortly!!!

Also, if anyone has the 964 shop manual and can scan the LSD pages then that would be a big help to all.

viperbob

The bearings are different on each side. Generally when I rebuild a diff, I replace the bearings anyway.

Paul902

If doing so, do you also have to replace the bearing races? That is beyond me for a DIY since it involves heating up the differential bell housing.

Also, do you replace the bolts that hold the ring gear on? I notice the manual says they should be replaced. Where can I source them from?

Paul902

I was thinking earlier today that it would be a good idea!

JasonAndreas

I'm stuck with a dialup modem, sorry.

Paul902

[QUOTE=Paul902]Thanks, Steve. I'll look at that approach. I am not sure if my bench vise is large enough to accomodate the diff, but it would be a good excuse to get a bigger vise.
QUOTE]

This must have been some kind of omen... last night I snapped the rear casting of my vise right off when I was having a go at this. It was an accident, HONEST!

On my way to work this morning I stopped at my favourite tool shop and they had a solid 6" Record vise on sale for $100. Unbelievable! The thing weighs 32 kg! There will be a slight delay in the LSD project while I get this mounted on my workbench. All in all, I'm pretty happy.

Garth S

Wow - a 6 incher - my Record is a mere <<blush>> 4 incher ...

At 32Kg, take an extra day to reinforce the bench too

Paul902

Last night I set up the new vise and used Chris W's suggestion of using the halfshaft flanges to brace the differential from turning. The ring gear came off with no problems.

Next, it is apparent that under the ring gear, the two halves of the diff casing come together at a flange on both halves that are held in place with 3 large Phillips head screws. However it is now obvious that removal of the bearings IS neccessary to slide the two halves apart to get at the internals. On my diff the casing under the bearings is cirular, but with two flat sides (You can see the flats of the casing in the first picture I posted). The shims also have corresponding flat sides, and I can see (at both ends) that the flats on the shims are not aligned perfectly with the flats on the casing Is it OK to try to get the bearing puller under these shims? I don't know how strong they are. The concern here is removing the bearings without damage to bearings or shims. In the WSM for 964, does it specify a puller, and if so, how many "arms" does it have? Please advise...

viperbob

I use a 2 jaw puller at the indentation points on the diff. You just have to be careful pulling them off. Yes sometimes the shims can get damaged so be careful. For installing the bearing, heat them up first and they will drop on.... The shims are pretty fragile. If you tear, bend, or kink one it should be replaced. If you do replace one, even though the are pretty precise you should measure the one you are replacing and the new one going on with a caliper. I find that there is some variance in these that can change the settings....

Paul902

Thanks Bob! I bought a 2-arm puller and removed the right side bearing with no trouble. After that I was able to pull it all apart. Next step is to get new friction plates and start putting it back together.

viperbob

Keep going Paul...

So do you have your rebuild kit yet? I generally find for the 993 that they are stupid expensive ($750 - 950 dealer list, yes you can get them cheaper). You wind up with a new, 2 clutch LSD that will be worn again very quickly. For a shop doing it with the cost of labor (obviously you are doing a DIY), it is just a little more to do a new Porsche Motorsport or Guard LSD. If you just want a TBD (torque biasing diff ala Quaiffe type) then it is almost a wash. On my car I installed a Guard unit and sold my dead diff on eBay. Thought I might get $100 or so. It went for almost $900 and I even said that it was dead and needed to be rebuilt in the ad. Crazy...

Keep going...

Toga

Excuse my ignorance, but even my Harraps dictionnary doesn't have it: what are the shims?

Great job Paul! Could you post pics from the LSD opened?

Cheers

viperbob

Shims are the metal spacers that sit between the case and the bearings you see in the photos. This allows you to position the differential in the proper spot left to right so that you have the proper pinion contact. It also allows for the full width of the bearings side to side to have proper preloading to the races which are in the case and the cover. Does that make sense?