Waterguy

I have a 1989 951 with 113k miles. It came standard with LSD and transmission cooler, being an '89. This year it started making 'groaning' noises while accelerating hard out of corners, which I initially atrtributed to LSD clutch shudder. At this fall's DE, one of my PCA instructors listened to it and told me, based on his personal experience with 951s, that this was slack in the spider gears. He also told me me that this is common in 951s, and that I was lucky that the differential was relatively cheeap to have rebuilt with the spider gears shimmed.

I had planned to do a tranny oil change this winter (its been two years) to make sure it had friction modifiers for the LSD clutches. I was also going to replace a known bad, but not noisy, inner CV joint, and hope that the noise goes away. Today, however, it has started to clunk and judder on hard turns, particularly backing up, which suggests that the spider gears may be the problem.

I have been following this forum for 3 years now, and have not heard anything about a need to rebuild 951 differentials or shim spider gears periodically. Is this a common problem? Or will this particular car not be happy until every last component is rebuilt/replaced? Is this a reasonably inexpensive fix, or was this a 911 driver talking? Finally, what else should be done "while I am in there?"

Any help much appreciated.

Mike S

Well, my personal experience is with two 944's both have/had over 120k on the clock with no rear diff problems. I imagine a lot of this has to due with preventative maintenance though. It will not be a cheap fix. If the posts on the board are correct, I estimate the repair to be in the 2k range.

Rich Sandor

Hi Don!

I'm not so sure I can help you here, but I am buying Mark's 89 951 LSD tranny w/ oil cooler, and will be putting that in my car.

Perhaps you should buy my used 86 non-LSD tranny w/ oil cooler and install a GT or Guard LSD in it. That way you can still drive your car while fixing the tranny yourself, and then just swap the trannys and sell the old one afterwards.

something to think about..

-Rich

PS, are you interested in the PCACWR TBC Karting Championship? I just sent the email to the memberslist.

theedge

IMHO "while youre in there" stuff should be all the CVs and the transmission mount.

But again it depends on the wallet factor... "While youre in there" could snowball into a tranny rebuild if you feel like it...

84black944

Sorry for the highjack but where may i purchase a guards diff

Waterguy

Thanks, Rich, I'll consider that. The time restriction is not that a deal, I can pull the car off the road over the winter if I need to.

I had planned on doing at least some of the CVs while I had it out, Brian, but the tranny mount is a good idea. I was thinking more along the lines of a tranny rebuild, I guess, although that could get costly fast.

So far, it doesn't look like many Listers have had trouble with their spider gears, although I agree with Mike that it may be an inherited lack-of-maintenence issue. I will get under there this weekend, since I am still holding out a faint hope for a bad CV. Sure feels like a chipped or broken tooth on a spider gear, though.

hosrom_951

Rage2 went through 2-3 transmission rebuilds due to 'breaking' the 1st and 2nd gears (too much power along with had shifting maybe?)

He had no problems with the stock diff, there was a thread about this where NZ951 posted a topic regarding transmissions/diffs 2 weeks ago or so, try searching

Waterguy

Lots of information about ring and pinion gears in differentials, Hosrom, including the post you referred to. I have never heard anything about spider gears wearing/breaking. Thats why I posted. it sounds like it is a rare or at least unusual problem.

hosrom_951

Well, Rage2 knows all about this, hope he chimes in

rage2

I've only broken 1 tranny. Stock except for autothority chips, so about 270hp flywheel? A lot of drag racing, 6000rpm launches, full throttle shifts. 1st gear lost a tooth, 2nd gear syncro was messed up. Next to no roadcourse lapping.

Tranny #2 was fine, even with drag racing and 460whp. It didn't come with an LSD, so I took the LSD out of the 1st tranny and used it in this box. The difference was no launching, just clutch slip off the line, and no powershifting into 2nd gear. Powershift into 3rd gear no problems. Lots of roadcourse lapping too. Still have this tranny as a spare.

I replaced that tranny because I got a cup car tranny that had strengthened 1st and 2nd gears, steel synchros, and oil cooler. Not sure if I needed the oil cooler, just a peace of mind deal.

The LSD seems to last forever... for me anyways. My car works hard .