G50 Transmission Question

[Jesse16]

Leaving a DE yesterday evening, noticing my 87 seems to have alot of "slop" or jerking as I get off the throttle and back on. Clutch seems to be working fine and I took a quick look at the Axles with a flashlight and the bolts all seem to be in place.
I'm hearing and feeling new stuff a bit during shifting and like I said, seems to be a lot of play between the motor and tires. Once I was moving steady, seems OK. Also, not sure if I'm hearing new noise from the tranny at steady state, its kinda loud in the car anyway. I had no problem shifting up through all the gears.
My plan, 1. get it up in the air and re check the axles and bolts.
2. ?????
3. Pull the tranny drain plug and see what falls out or is stuck to the magnet.
4. If the clutch still works, I can't see how that would be a problem. I still have the rubber center clutch so if it failed, I'd just be sitting still.
Car has 199 k miles.
What else to check?

[Peter Zimmermann]

Sounds like clutch to me, the disc hub just hasn't failed enough to prevent shifting gears.

[Jesse16]

Very interesting, as usual I hadn't considered that it could fail partially. That does make sense with what I'm feeling and if it has to come apart, that's a much more desirable outcome than a bad trans.. The clutch was replaced once at 105k miles with the stock porsche rubber center part. That was 12 years ago.

[lupin..the..3rd]

Could be rubber clutch. Or could be transmission mounts. When the mounts go, it'll shake and vibrate as you're getting rolling and letting out the clutch, then be relatively smooth while driving.

Use the mount kit from Wevo. Have your local machine shop weld in the cups. I went with blue pillows and didn't really notice any new NVH.

[Jesse16]

Thanks, good thing to look at. Should I be able to "see" that failure ? Take out one or both bolts while supporting that end and move things ?? to see the failure. I feel like I have "alot" of slop going on, not just a small amount and it happened fairly abruptly.

[KTL]

Failed mounts are usually obvious, as they allow some movement of the engine or trans. The movement allows the big cup washers to get mangled by the torquing back and forth of the mount.

I agree it could be the clutch hub. The purpose of the hub is to soften the transfer of power from the engine to the transmission. So the clutch disc actually twists to dampen the action of engaging the clutch.

Another thing to check is the axle shaft, not just the CV bolts. Grab the shaft and turn it back and forth. There should only be an ever so slight amount of play in the shaft when you turn it in such a way. If there's a lot of play, you need to rebuild or replace the complete axle assembly. Note that i'm saying rotational play. The side to side play is quite a large amount and supposed to be that way, to allow for the pivoting of the axle

[wildcat077]

This is what an "exploding" rubber centered clutch disc looks like ...
Mine let go at 6000 + rpms braking and downshifting into third gear going into Caroussel at Circuit Mont Tremblant!

The shifter just jammed in between gears and i had to coast to a stop ...

Cheers !
Phil

[Peter Zimmermann]

I've seen them break like Phil's did, but I've also seen them fail where the rubber section split, but not enough rubber chunks got loose enough to jamb the pressure plate. The split will cause the jerking sensation. Jesse, when your car is apart be sure that the appropriate updates get done to the release fork assembly (they were probably done at the first replacement, but new bearings, etc., sure won't hurt).

[Jesse16]

I'm liking (if thats possible) the failed clutch theory. I'll check those halfshafts and mounts but think the clutch is more likely. At least I know how to remove the engine and now have the tools. When I tear it down, I'll take a photo. Maybe should replace all 4 rubber mounts anyway this time as they're also 24 years old.
Have to think about the tranny as its a bit touchy going into 2nd gear but thats another long stretch of costly repair road.
I had the entire thing apart last winter for top and bottom rebuild and as cost was escallating, decided not to replace the clutch parts, all measured fine and looked OK. My release fork assy. was noted as being re-done way in the past at that first clutch replacement and very simply rides on what looked like brass bushing, seemed nice and snug. No needle bearing or junk inside to fail. Think I'll look at it all with a significantly heightened sense of interest the second time.
Pulling the motor a second time will classify me a semi dangerous amateur.

[Eric 88 Carrera]

I have something similar going on. The car shifts fine, but there is a lot of play when power is abruptly applied and when power is abruptly removed. I had the car up on a lift and there seems like a lot of backlash when you rotate the rear tires. I was told by my mechanic that this is due to a worn ring and pinion gear in the transmission. Is this also a possibility?

The car has 102,000 miles on it and is still on the original clutch. I would much rather replace the clutch than send the gearbox out for a rebuild. Anyone have any thoughts?

[Jesse16]

Are you talking about how much the wheel on one side should rotate if the opp. side is held firm ? Or just lift one side, how much "slop" can one expect ? Be interesting to hear what amount of rotation in degrees is normal. Does it matter which gear the tranny is in ?

[Peter Zimmermann]

Originally Posted by Eric 88 Carrera

I have something similar going on. The car shifts fine, but there is a lot of play when power is abruptly applied and when power is abruptly removed. I had the car up on a lift and there seems like a lot of backlash when you rotate the rear tires. I was told by my mechanic that this is due to a worn ring and pinion gear in the transmission. Is this also a possibility?

The car has 102,000 miles on it and is still on the original clutch. I would much rather replace the clutch than send the gearbox out for a rebuild. Anyone have any thoughts?

This might be one of the, well, I won't go there, but just think about the noise that you'd be hearing if a ring & pinion "gear" was worn to the point of having unusual backlash. Please, do yourself a huge favor; don't ever let the "mechanic" that said that work on your car!

[cashman]

Hi Jesse,
Not much to add here but a simple hello . I was the silver cab that sat next to you all weekend. Glad you at least made it home ok. Good luck with the repair.
Mark

[masterdave]

coming in here from another angle. I had what sounds like a similar issue recently. When I hit the gas hard the car lurched a bit as it accelerated. It got worse some times and some times was not even there. Some times it was so bad it threw mw forward a bit. It turned out to be very very dirty spark plugs. Put in a new set and the car ran like a charm. May be some thing worth checking.

[dshepp806]

clutch..

Doyle

[Jesse16]

Glad to find you on the forum Mark. Thanks for the encouragement and I enjoyed hanging out with you waiting to drive. You had a great DE weekend and instructor. I'm not completely unhappy that I have a winter project now although I wouldn't have minded skipping one winter with the engine out. Motor will be out in the open by mid Dec. and I'll be putting it back in by early Jan. (is the plan). Also planning to rebuild the pedal cluster to solve the minor throttle return issue. Install my new ATO Fuse Panel (original christmas gift) and maybe clean up my custom H4 headlight install. Wasn't supposed to be a costly winter part buying exercise.

[Nine9six]

Originally Posted by Peter Zimmermann

I've seen them break like Phil's did, but I've also seen them fail where the rubber section split, but not enough rubber chunks got loose enough to jamb the pressure plate. The split will cause the jerking sensation. Jesse, when your car is apart be sure that the appropriate updates get done to the release fork assembly (they were probably done at the first replacement, but new bearings, etc., sure won't hurt).

+1 on what Pete said...

[Jesse16]

Simple question, do I really need to replace the pressure plate if I tear down and find my rubber centered clutch plate has failed ? Is the pressure plate a failure waiting to happen ? I'd still replace the throwout bearing and I see a guide tube is recommended. Don't remember seeing that part but must be in there.
Did some search and reading and looks like some folks do a thorough inspection, cleaning, and if all is flat and true, maybe a light de-glossing of the surface. I was having no issues with clutch clamping pressure prior to clutch failure.
This would cut part costs in half so worth considering. Probably play it by ear and decide how much I hate the thought of another engine removal.
My records say a Clutch Kit was installed 90 K miles ago.

[Packet82]

Originally Posted by Jesse16

Simple question, do I really need to replace the pressure plate if I tear down and find my rubber centered clutch plate has failed ? Is the pressure plate a failure waiting to happen ? I'd still replace the throwout bearing and I see a guide tube is recommended. Don't remember seeing that part but must be in there.
Did some search and reading and looks like some folks do a thorough inspection, cleaning, and if all is flat and true, maybe a light de-glossing of the surface. I was having no issues with clutch clamping pressure prior to clutch failure.
This would cut part costs in half so worth considering. Probably play it by ear and decide how much I hate the thought of another engine removal.
My records say a Clutch Kit was installed 90 K miles ago.

If the pressure plate has 90k on it, replace it with the clutch. You'll have problems with it at some point. Even if it hasn't been a problem yet, you might as well do it right the first time around.

[Jesse16]

So got the engine out, tranny separated, and thankfully my problem is the rubber centered clutch.
You can see where the rubber has parted away right at the disc. This lets the disc rotate about 20 degrees in each direction rotationally before the cleats on the back side grab some and allow the thing to push. I'm amazed it continued to work at all for 150 miles for me to drive home. Parts will be on order in a few days and it'll be back together in about 2 weeks. Also do a couple of "while its apart" tasks but really most was done last year during rebuild.