Transmission CLUNK when clutch is disengaged PT2

thoen · 08-17-2008, 07:46 AM

Hello,
i posted a while back on this and I think I better start again. I replaced my Transmission mounts and CV joints yesterday. The problem I am trying to solve is, where does the CLUNK sound come from when I dis-engage the clutch to go into gear? My clutch was replaced about 1 1/2 years ago. This sound is not always there but when I am at a stop or going into 2nd gear, I release the clutch and half the time it clucks, metalic-sounding, from the trans. what else can I look at? Did anyone else have this problem (I am sure!).

Off subject: Anyway I heard that the 944 got a high rating in the sept. 2008 AUTOWEEK. anyone see that?

firefighter7128 · firefighter7128's Garage

Fly Wheel?

thoen · 08-17-2008, 07:58 AM

The sound is coming from the back. I can clearly hear it from behind the back seat. It is the transmission. I don't understand how the flywheel could cause it? There is a lot I don't know but I know the flywheel is by the clutch up front. and all it does it is keep the engine running smoothly. I think?

Techno Duck · Techno Duck's Garage

Take out the rear hatch carpet and drive around. It insulates alot of the sound..with it out you will hear almost everything going on back there.

thoen · 08-17-2008, 09:20 AM

hi jon,
i took out the carpet (replaced the whole thing!). the sound is from the transmission. i can pin point it. could something be wrong with the trans? The car otherwise runs great, but i fear that something might be going wrong. This happens when I "let go" of the clutch but not all of the time.
ernest

Schumi · 08-17-2008, 11:17 AM

I also have a clunk when I let out the clutch, the quicker the more noticeable. It is also only intermittent. It happens almost in any gear allthough it is rarer the higher the gear. It only happened when the driveshaft would be spinning at a different rate than the engine IE take off from a stand still. I always believed I had a worn rubber center clutch (my clutch is original) and it was the rubber spinning up to speed. I cannot tell where in the drivetrain it comes from but I do not think it is internal to the gearbox nor further forward than the clutch. So that leaves clutch and torque tube.

I avoid it by consistant rev-matching on shifts and never dropping the clutch quickly or doing stupid things like burnouts and such. To the point I never hear it. But when anyone else drives it they have problems with 'finesse'-ing the clutch pedal and matching revs. I do not believe the problem to be damaging for some reason as I have put nearly 4000 miles on the car like this and a lot of them have been very spirited driving.

It almost makes me think of two sides of a U-joint where the link in the middle has been broken, therefore if the halves are not spinning together the one has to spin up and hits the other before they both start spinning together. Making a metallic clunk. But I do no believe the toruqe tube houses any such joints. It is a straight splined driveshaft as far as I know.

Does this sound like what you hear?

2Tight · 11:48 AM

I drove my 83 with a bad clutch for too long (the tabs were banging). After replacing the clutch I could really feel the wear it had caused on the ring and pinion. One way to test it is jack up the rear of the car on stands with it in gear. Remove the rubber inspection cover and try and twist the driveshaft. With a good clutch the shaft won't rotate at all. Now rotate each wheel back and forth and see how far each travels before it makes contact internally; again listen for clunks. If there is a lot of play on one only and makes a solid clunk I would say one of your output shafts are worn. Next you can have someone depress the clutch and see how much rotational play is in the shaft before you hit resistance in the trans. If it rotates more than about 1/8" I would say your R&P is very worn. Make sure both sides of the shaft at the coupling are solid and turn together. Any trans will make some noise when tested like this but it's the amount of travel back and forth that will tell you the most. Don't discount a bad CV since these are very easy to check turning the wheels while holding the axle.
Hopefully you will find where it's coming from and it turns out to be external.

Schumi · 01:02 PM

Sorry for hijacking this thread but I've probably got the same problem and I have never truly diagnosed it.

edit-

So that didn't take long- I just went out and slid under the car without jacking it up first (I'm thin..). Took the inspection cover off. Everythijng inside looks brand new obviously. The spline input shaft was firmly on the driveshaft. With the car in nuetral and the tires on the ground I grabbed the driveshaft with my hands and can spin it mildy freely for 1/8th of a turn. when it spun and stopped in one direction it made the same knock it makes when letting the clutch out.
With the car in 1st gear I can still spin it a bit but not as much. About half as much I'd say. As the car is in gear and the clutch is not depressed, there should be no play I take it. But even with the tranny in nuetral... with the clutch not depressed I still shouldn't be able to turn it at all?

So this is a probelm with the clutch I assume. I'd much rather have a clutch problem than a R&P problem.

edit #2-

I just went up to do the same test on my other car and there was no rotational play whatsoever. This doesn't look good.

thoen · 08-17-2008, 04:24 PM

Thank you guys!!!
schumi, your problem is exactly mine. thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

2Tight · 08-17-2008, 04:55 PM

I never thought I would hear "I'd much rather have a clutch problem" If it is the R&P it's generally cheaper to find a good used trans anyway. Even in neutral you shouldn't have much rotational play in the shaft so looks like you'll be doing a clutch job. Looks like Shumi needs a clutch but in Thoen's case I have to assume the rubber center clutch replaced 3 years ago was with a spring center clutch so I would dismiss the clutch as being bad. The spring clutch does not have the limp home tabs that make the clunk that Shumi is hearing and verified by play in the shaft. Even minor wear on the tabs was enough to cause accelerated wear on my R&P on my 83.

thoen · 08-17-2008, 05:33 PM

foregive my Naiveté, but is the ring and opinion an inside part of the transmission? easier/cheaper to replace the whole thing than to refurbish the trans?

thoen · 08-17-2008, 06:16 PM

ok, so I read up. it is the differential. can i just replace the differencial if the ring and pinion are bad???

2Tight · 08-17-2008, 06:30 PM

Quote:

Originally Posted by thoen

ok, so I read up. it is the differential. can i just replace the differencial if the ring and pinion are bad???

Again it will just be cheaper to replace the entire transaxle than a ring and pinion. Setting all the clearances on a R&P is a trial and error and best left to a good shop...even then it's a crap shoot. You can find lower mileage TA's for $250 to $400. Taking yours into a shop for a R&P repair will cost you 3 times that. Again, just an opinion you might consider.

thoen · 08-17-2008, 06:39 PM

ok. so the clang noise in my car is the worn ring and pinion is due to the bad clutch that should have been repaired earlier. i replaced it the first week after i bought the 1983 944. The clutch caused the problem.
i think i am able to the the trany change using clark's garage manual. is it a long job? i remove the cv (again!!), remove the linkaget bar and unscrew the trans from the retainer. pull back and out the transmission. sounds easy.....

Schumi · 08-17-2008, 06:55 PM

Like some others on this board, I'm not made of money nor time right now.. paying a shop to do the clutch will never happen and doing it myself would put the car down for months if not longer, plus the fact that I already have 1 project car that is getting a full rebuild limits space and patience to do the job.

Looks like it will just get driven less and the clutch job will have to wait. It's lasted for years like this, it will last a little longer. I bet a lot of people cringe at that but I'd rather drive it and enjoy it while it lasts than run my finances into the ground fixing it at this point. And I could never sell it like this, I would feel like I would either A) cheat the new owner or B) lose a ton of money as the car wouldn't go for beans with a known clutch issue....

thoen · 08-18-2008, 08:22 AM

ok. so is the ring and pinion the parts that transfer the power from the shaft to the cv joints? is it part of the differential? can i just replace the differential to cure the R&P problem?

Schumi · 08-18-2008, 12:55 PM

Theres the input shaft to the transmission. This goes back to the gears. The gears output back forwards to a pinion gear. The pinon gear is a small beveled. It connects at a right angle to a very large beveled ring gear. This ring gear is what attacheds to the differential.

The R&P gears take a lot of load and they can wear and chip teeth.

Techno Duck · Techno Duck's Garage

I follow the same school of thought as Schumi, for a n/a its cheaper to find a used transmission and replace it. Unless you have something special like a LSD, i wouldnt bother rebuilding it. Your looking at well over $1000 to have the transmission rebuilt and that does not include the labor to take it out or put it in.

You can find good used n/a boxes for under $500. There is some risk buying a used transmission, but theres also the same risk having the transmission rebuilt hoping whoever did it knew what they were doing and did it right. Case in point, the transmission on my 951 was rebuilt by the previous owner, returned 1k miles later because it was popping out of 2nd gear..work was under warranty though.. problem solved.

thoen · 08-18-2008, 01:31 PM

Thanks!
if the R&P noise is minimal, should I start worying and prepare a for a replacement transmission now or wait till it is REALLY loud and regular?? What is the worst case scenario? will there be any danger to me if the part totally screws up...would it seize my transmission or what???