Guy

Hello All!

My 79 is coming along nicely but I have a couple of annoying issues to address. I need your help!

I replaced the clutch as soon as I got the car as the old one was literally torn apart. The car has 74k and I did not replace the throwout bearing nor did I lathe the flywheel. I did give it a quick surfacing with 220 grit emery cloth and checked it for true.

I have put 200 miles on the new clutch. Shifts nicely and operates well with ONE exception. It has a "shudder", "chatter" or "judder" when first engaging first and reverse. If coming off a slight rolling start, it can be avoided all together. A quicker low rpm engagement also seems to eliminate the problem. It is possible that is has improved over 200 miles but it is more likely that I just am getting used to it.

When it does shudder, people observing my car tell me that it looks like the rear wheels are going to fall off the car

I also get a moderate amount of vibration thru the shifter.

When I did my axles recently, I noticed the tranny moves around quite a bit and quite easily both side to side and up and down. Doing a search reveals that my trans mounts do look flattened.

My engine seems to sit at proper height, yet I get a fair amount of engine movement at idle. I attributed this to the state of tune as the car is still being tweaked. It should be noted that all readings are rock steady during the engine "rumble" (vacuum and rpm).

I am thinking my clutch shudder is due to the worn trans mounts. The engine mounts may also be attributing to it. Here is what I am asking:

1.) How should I check the engine mounts? Back in the old days, we would torque a motor and observe the mounts.

2.) Any measurements to check?

3.) Any cheaper alternatives for the trans mounts?

Here are pics of mine, the one side looks worse:

Mrmerlin

to stretch the trans mounts life ,
get a piece of rubber (from a car tire would be good) then carefully jack up the trans till the upper part of the mount comes off the lower part ,
slide the tire section into the opening,
then lower the trans.

Note this will lift the trans back to its proper position,
it may transmit a bit of vibration but the trans wont be able to touch the cross member

Guy

I have no problem replacing the mounts if needed BUT your suggestion may be a good way to test my hypothesis that this is contributing to my clutch shudder. Thanks as always!!

tmpusfugit

You may rethink that when you find the current price on the transmission mounts....

Guy

Yeah, I saw that they have risen dramatically. It also seems that I can use the 78 mount, 92837504513 instead which seems to be a lot cheaper

Hilton

Ok, I wasn't aware that there was a 78 mount.. interesting.

I have new mounts on my 89 which I bought 5 years ago and paid $65ish each for.. before they went up to insane prices. My 87 needs some however.

Anyone know what the difference is in physical dimensions between 928 375 045 13 and 928 375 045 16? The pics above similar to the later ones.

Guy

I inserted some shock bushings into the trans mounts today. I wanted to see if it would lessen my clutch shudder.

Verdict......possibly I just can't tell.....I do get a bit less shake at the shifter.

I am going to get to this job in the very near future. Even with the height increase from the added bushings, the rubber is still broken down and soft and likely not a good test. Even if it doesn't fix the shudder......I need them either way.

I may experiment with the 78 mount

pdejong

I talked to Hans Servaas at SITM this weekend. He has developed a new set of trans mounts, polyurethane and harder that the stock rubber mounts. He is almost ready to produce them. No idea what he is asking for them , but I am on his list for a set.

Peter deJong
Charleston SC
'90 GT-TT

Jadz928

Interesting that your considering using the larger right-side mount. On both sides I assume?

Its larger (wider) because the battery box is cantilevered off the transaxle on the rear left. So they used different mounts (left and right) to compensate for the weight bias. 78 only.

So if you used the wider mounts on both sides on a 79--> , you will have equal dampening, but not as much dampening. I guess the question is will the frequency of the transaxle fall into the useful range of the wider 78 mount? Good question. And you're just Guy to find out.

Guy

Yep, part of the fun is the HUNT and deal I am glad you posted, Jim. I always thought the left side was the larger one but now that I think about it.....

The passenger side (92837504613) is actually cheaper that the driver side (92837504513)

I think my clutch is going to have to come out again either way but I am going to put another few hundred miles on it to see if it improves.

Hilton

Crazy.. three different trans mounts available..

92837504613 - $59
92837504513 - $74
92837504516 - $138

So.. do the large earlier ones (the cheapest) fit the later crossmember/transaxle? Or do the smaller ones?

Guy

613 is the small left mount for 78
513 is the larger right side for 78
516 is the post 78 style, same for both sides. $138 for that mount seems on the cheap side.

They all will fit, different upper bolt (length) may be needed. I may try using the 613 on both sides.

Hilton

Prices I quoted are all from a Porsche dealer in CA (MSRP for the later one is $169.39).

Guy

I received my mounts today, these are the 513, large mounts. Haven't fitted them yet, new upper bolts will be needed (M12 1.5 x 80mm).

Simply put, these are BIG! It will be a tight fit on the right side but should make it in there. Will keep you guys posted.

Hilton

While they're out of the car, can you post some measurements?

1. From outside edge to outside edge (i.e. the "shoulder" width)
2. The narrower part that bolts to the trans

Thanks!