Potential expensive drivetrain klunk

[Paul Glasson]

Perhaps someone has advice on pinpointing a drivetrain klunk that developed last week.
On taking off in first gear there sometimes is a klunk which feels like a baclash problem in the drivetrain.It is mostly noticeable after slowing down under compression to a stop then taking off normally, and seems to be coming from the middle of the car but could be mistaken.On a flat road have tried taking off in first then stopping,selecting reverse and taking off,then repeating first again, and cannot reproduce klunk that way, which makes me suspect it is not the engine mounts.
Immediate thought is the rubber on the clutch disk or mabe a universal on one of the back wheels. Any thoughts PLEASE?

A by the way.Friday evening my car broke down on a really deserted ramp leading onto a highway,and my 18 yr old daughter was in the car.Stuck there for a 1/2 hour and not one person stopped as people here afraid of highjacking etc.Cops eventually came past on route to an accident and took my daughter with,as they said it was v dangerous and we picked her up with the breakdown van on route-was fuel and a false gauge reading.Probably an earth

[idontknow]

I posted this in another article but it might help

Check the CV joints. Jack the rear end up, you only need to jack up one side to test. Put the car in 1st gear and rotate the rear tire back and forth. hold the CV joint /driveaxle in one hand and feel the difference of movement. If a/many cv joint/s are bad, you'll probably hear the clunking but definitely feel a difference in movement. eg. CV joint moves, drive axle does not = bad CV joint. If the CVs are good and you think it's the ring and pinion, pop the little inspection plug from the forward nose cone of the tranny and rotate the tire again. If the driveline shaft doesnt move but the wheel does, it's in the tranny. If the driveline shaft does move, it's not in the rear end.

Hope it helps. I had all 4 CV joints bad when I got my car. The car made a clunking noise every time applied power or shifted. Didn't think too much of it. Eventually one of the CVs started making BAD clunking noises whenever the car was rolling. After replacing the CV joints I found that the clunking action was also eroding the R&P. $320 for 4 new CVs and $1200 for a rebuilt tranny and I/my bank account have learned a very valuable lesson.

Hope it helps

[Paul Glasson]

idontknow,thanks for the input-really hope it is the CV's and not clutch or transmission, will be a bloody lot less expensive than clutch.Slipped up calling it a universal,those are on cars prop shafts which the 944's don't have.
The driveline shaft-you referring to the shaft running in the torque tube I guess.So I would need to have it in neutral to do that test and not 1st?To all intent the car runs quite normally,and clutch feel is the same as before,just that there is the backlash and klunk now.Thanks

[SoCal Driver]

If the CV's are bolted tight then it's the clutch plate.

[Paul Glasson]

Ok,I jacked the one back wheel off the ground at a time and checked the CV's-The outers have no play,but the inners there is about 1mm (1/16")travel on the outer circumference of boot retainer in relation to the shafts.This could be the clearance fits on the splines and not the CV's perhaps?When rotating a wheel there is about 1 1/4" travel on the wheel outer circumference before movement on the drive shaft is noticeable.Other cars I have had I have noticed similar backlash but perhaps idontknow or you socal are more familiar with the normal backlash travel on these cars.The car is starting to make a slight diff whine on decelerating against compression in 1st and 2nd,but nothing serious(150000Km mileage).From what you guys say, symptoms are pointing to the ring and pinion or clutch. I don't have the facilities/space to do a gearbox job so would mean a garage and $$$.Thanks for the feedback.

[idontknow]

Is it a really loud clunk? It may be the engine or transmission mounts gone bad. You may want to search for more insight into the mounts and the telltale signs that they're going. 1 1/4" is alright as long most of it's accounted for in the CVs. The ring and pinion are bound to have "some" play affter a lot of mileage. Plan to change the inner CV joints in the future though.

Hope it Helps

[Paul Glasson]

Not a really loud klunk,and it does not happen every time, but that would depend on the engine braking effect before pulling off in first again. Cheapest option would be to have the inner CV replaced and see if the noise goes away. When I get the time will take off from work and get my mechanics opinion and a quote. Blast-was hoping to have cosmetic repairs such as spoiler and wheels repainted and door dings removed this month.

[Paul Glasson]

Horrors horrors,
My mechanic has inspected my car and done a major service including tightening Balance and cam belt and filling engine and gearbox with Mobil 1. He says the Klunk is coming from the gearbox, which is probably the crown and pinion. He is going to put me on to a gearbox reconditioner but I do not know if they will be familiar with dropping a 944 gearbox. I will have to weigh up the costs and see if it is worth keeping the car and what I would get for it as is. Does the 944 have Audi parts for the gearbox and can you guys tell me which model parts is compatible?
I am really sad as I have thoroughly enjoyed driving this car and hope I do not have to let it go.

[..P]

A loud clunk coming from the gearbox, eh? Somehow I don't buy that one.

It may be true, but i would think it was the clutch.

As for a can of "gearbox reconditioner", all I can say is "good luck" because you can't get a mechanic in a can. If it's a physical problem making a clunk, chances are slim to none that it will work, but hey, give er a try.

I use Amsoil Series 2000 75W90 gear lube (synthetic) and it does a great job, easy shifting and quiet too. It's better than the Mobil-1 equivalent as Mobile-1 does not meet the GL rating required by Porsche. Probably doesn't matter though, as most synthetics run so cool the oil never gets hot enough for the sulphur content to go after the yello metals in the tranny.

regards, P

[pokey]

I think by "gearbox reconditioner" he means rebuilder.

[..P]

I hope the "rebuilder" has two hands, as it's tough to find something in a can that will fix a physical mechanical problem.

P

[ae1969]

To me it sounds like the Tranny mount. Mistaken for many clunking sounds...... This does not sound like a CV ....and an internal internal tranny clunk.....uhmmmm I dont think so either (you should be able to reproduce that)

Put the car on stands then pull the rear tires off. You should be able to see the mount by looking over the tranny from the rear wheel area.

Look for any places that may have metal-metal contact.....

Took me a couple of months to figure it out.... intermittent, on quick acceleartion/deceleration, sometimes on a sweeping turn while accelerating.........

Good luck.

[Paul Glasson]

Thanks for all the feedback-I have learnt a good lesson with this one-get a second opinion from a Porsche qualified mechanic and the forum. After my present Porsche mechanic told me it was the gearbox, I went to the gearbox reconditioners and they could not tell me definatively where exactly the problem was, and would only be able to give me a clear answer and the $$$ cost once the box was out.
Then went back to my original Porsche agent who I could no longer afford.He is willing to guarantee it is the rubber discs on the clutch that have come loose from each other and the drive shaft is rotating until there is metal on metal contact on the stops associated with the clutch rubber discs-So once again SOCAL IS RIGHT.
The Porsche agent tells me the easy way to check is put the car in neutral, go to the inspection hole on the nose cover of the tranny-if the drive shaft can be rotated say 30 degree either way the rubber is gone and shaft rotates until the stops on the clutch disc prevents further rotation. I tend to go with that as the problem was not something experienced gradually but happened over night. 20 year old clutch,150K km and autocross, suppose something must go.
Good news is the original Porsche mechanic is going to fit a new clutch plate and pressure plate for R5000 (approx $715) which I think is pretty good,he assures me I won't have to pay for the clutch job if the problem is the gearbox and not the clutch. So there goes my cosmetic repairs for a short while.

[SoCal Driver]

I only repeat that which I have learned from others and my own experiances. Thus the reason for this forum -- learning.

[Z-man]

Originally posted by Paul Glasson
He is willing to guarantee it is the rubber discs on the clutch that have come loose from each other and the drive shaft is rotating until there is metal on metal contact on the stops associated with the clutch rubber discs

Being a Johnny come late to this thread, I am too late with my prediction of the rubber clutch hub being the problem. I test drove plenty of 944's in search of mine, and many of them exhibited this problem.

Klunk + backlash = bad rubber clutch hub, 99% of the time.

-Zoltan.

[flangermog]

Bit of a jonny come late myself, I had a very similar problem, and even the Porsche main agent told me it was the gearbox, which they would happily replace for ££££s. The symptoms I was having were very similar to these, although a little more developed.

Phoning around for re-con gearbox, I speak to a chap at a well known porsche specialist in Bolton (UK) who says that he would bet the cost of the job on it being the clutch. He even showed me. And it was.

Hmm, I wonder if the porsche dealer would bet the same on it being the gearbox...

[Paul Glasson]

OK,so I visited the Porsche agent this morning to see buggered clutch plate (rubber discs were torn) and to speak to him about not being able to supply both pressure plate and clutch plate for the R5000 he quoted. Says they are not available through his supplier and I will have to wait at least 2 weeks if I want both at the price quoted. He can supply the pressure plate only by buying it from the Johannesburg agents for R3200 (total quote was R5000 before tax- $715) and the job will still cost the same (I confirmed the cost from Johannesburg).I am over a barrel as I cannot be without the car for 2-3 weeks. So he is using the old pressure plate and a new clutch plate. The pressure plate surfaces look good and he assures me all will be well.Have unfortunately heard too many bad stories about not replacing both with resulting clutch shudder. Well he will have to redo the job if that is so otherwise his name will be ****.

[SoCal Driver]

Paul, Also replace the TO bearing and give it's guide shaft/cone a decent dab of grease and you will be OK. You can get away with the old pressure plate for about two maybe three disks and the TO for about two disks. Note you can pop of the seal on the TO and cram some fresh grease into it.

I'm not cheap! Just very, very practical!

[ae1969]

Dont forget to resurface the flywheel while he is at it....

[Paul Glasson]

I'm in love with my car again. Clutch plate replaced with old pressure plate and no clutch shudder, gears are smoother to change, no gear meshing sound on 1st and second running against compression. Also the first to second gear change not so stiff or gratey it seems. Also had a broken door handle replaced. Hopefully nothing else mechanical goes wrong again. Car goes in for spoiler respray and stone chip and door dings on monday. Had a full service when the clutch problem was being diagnosed, so I have spent a fair sum on the car this last 2 weeks. Hope it does not let me down.
Thanks again to all those that put in their pennies worth on diagnosing my cars problem