944visage

First Post At Rennlist, and not a happy one:

85.5 944 NA with new clutch supposedly replaced by previous owner 40K ago. I suspect what may be obvious transmission failure of some type. I need help confirming diagnosis or additional things to check. I did a search here but had a hard time finding the right information for this problem.

Symptoms:

Rear End went CLUNK pulling away fairly agressively from a stoplight in 1st gear and spun the rear tires a little in the rain.

Car made it to side of road BUCKING and CLUNKING noise coming apparently from the rear and/or under the car.

Towed home after "driving" BUCKING and CLUNKING onto and off of flat bed tow truck (not pretty) since the truck winch cable was dragging the tires when we tried pulling it onto the flat bed.

Car idles fine in neutral and in all gears with clutch pedal in.

Car shifts into all gears fine with no noise.

Car does not roll very well in neutral, rolls then locks up rear tires.

Under car transmission inspection did not reveal anything obvious and no leaks.

Drained transmission oil which was full and used a magnet and strainer to look for metal particles. There were only two very small metal pieces found. One that looked like possibly a tooth tip 1/8" x 1/16" x 1/32" and another small piece about 1/16" x 1/32" x 1/32". The magnet also picked up a very small amount of metal shavings, but not much at all. This doesn't seem like much metal for a transmission failure, but I am a newbie to this car?

The clutch inspection hole showed the clutch to be about 60% worn (about 1.25" or 28mm gap between piston to edge of hole.

The clutch inspection hole cover has been missing since I bought the car about a year ago (forgot about it) and am wondering if rain could have gotten into the clutch housing rotting the rubber clutch disc center, assuming the previous owner put in that type of disk and not the updated one with the spring center.

Do the failure mode, symptoms, and preliminary obvervations sound like a clutch failure, transmission failure, or other?

I appreciate any help since this is looking to be a costly problem and don't want to buy parts that are not needed since I am probably going to do the R&R myself. Let me know what other items to check as well to further diagnose the problem.

Thanks in advance

Luis de Prat

Welcome to Rennlist. There are 2 kinds of clutches for these cars. In one kind the clutch disc has a rubber-centered puck, and in the other kind the disc has springs instead. The rubber puck kind is notorious for breaking even after relatively few miles. I've had this happen with a rubber-centered clutch only 45K miles after replacement.

From the symptoms you describe, I hate to tell you this, but it's likely that your car has a rubber-centered disc which is failing, and causing the car to buck and bind when changing gears.

Depending on how mechanically inclined you are, you could potentially DIY the clutch, but it does take a bit of time and effort to do. Kits are around $400 from various suppliers you'll see in the Rennlist sponsors page.

Again, I'm really sorry.

Dave

Your clutch is fine, you need a transmission. The weak link in the NA driveline is the ring and pinion, I've been through 3 and know that sound before I clunk to a stop. My first went shortly after I got the car as I was shifting gently into second at 3000 rpm. The second went 11 months later, 2 days after the car was hit by a truck (parked in gear, pushed it 3 feet). the last was about 2 years ago, foot to the floor when the light turned green. The labor is a whole lot easier than a clutch but a rebuilt trans is expensive. I've gone with used transmissions.
Sorry to be the bearer of bad news.

Luis de Prat

Gee Dave, either I've been really lucky with my tranny or very unlucky with clutches, but when I've had the symptoms this fellow is describing it was a bad clutch and my tranny is still going strong at 204K miles on my 83.

When the R&P in the tranny breaks, it was my understanding that it sounded like having a bunch of rocks in there.

944visage, one way to test the clutch is to put the car facing downhill and try to drive it in reverse. If it bucks and binds, your clutch is bad.

944visage

Thanks for the information guys.

A trusted mechanic of mine who races 944's told me the same thing as both of you did on the phone without looking at the car...ring and pinion..., but then said it could be the clutch as well but was leaning towards the ring and pinion. My search on this board showed a lot of talk about the rubber pressure plate failure and I am trying to get clarification before I buy a used tranny.

One clarification about my symptoms is that the CLUNK occurs when releasing the clutch in Reverse, 1st, 2nd, or even 3rd gear and has nothing to do with shifting gears since I haven't shifted the car since the failure.

Thanks for the info again and anyone with a used tranny they think is in decent shape for a 85.5 on NA 944, please email me if they have one for sale, assuming that's the problem.

Dave

Maybe I shouldn't sound quite so certain, I've never had a clutch go, but I'd heard that is "less violent" than a R&P failure, the fact that it's coming from the rear (transaxel) also makes me think this is the case. Wouldn't a clutch failure come from the bell housing? I guess there are noises that are deceiving in their origin.
A box of rocks is fairly accurate, although in my first case it felt more like one BIG rock that the rear of the car was trying to climb. My second one locked up completely, but made pretty much the same sound, the last one I just coasted to the side of the road (same sound) and called for a flatbed without trying it to find out if it was locked up or not. I now have a trans out of a 944S, same final drive ratio as a NA but the strenght of a turbo.

Dave

I guess you posted while I was typing. How does it drive once you get it in gear? A clunk going in and out is more likely to be the clutch I would think, but bucking while moving at walking speed is R&P.

944visage

Dave,
I think your right about R&P...BUCK and CLUNK at walking speed since haven't been able to get the car to drive past 1 mph on and off the flat bed, into my garage, then out to a parking space for storage since have a single car garage. It made one hell of a noise trying to get it about 10 yards in both directions. Thanks for the input Luis and if you still disagree based on this further information please post again since you guys are helping a lot.
Steve

944visage

One more thing about the R&P failure diagnosis:

Dave, did you find a bunch of metal in the tranny oil or did you check? That was one of the reasons I thought it could be clutch? As my original post mentions, very little metal was found in the oil, but I suppose fragments could have just settled in the housing via gravity and not been drained out since the drain plug is on the side? I suppose removing the tranny will tell more, but am hoping to do this R&R in one session.

Dave

Not exactly the way we like to help, I wish the news could have been better.

I never checked the oil, the first two actually cracked the housing, the first from driving on it I think and the second was cracked in the accident and failed when it ran dry (or at least that's what we told the insurance co.). The third should still have oil in it but I don't have access to it right now.

Dave

I just remembered...I've seen a few pictures of disassembled trannys with bad R&P, the ring gear seems to break into big chunks that would not drain out with the oil. All you would be likely to find would be a few shards from the ring gear and maybe a tooth or two that stripped off of the pinion. Does that sound about right?

944visage

Just found two particles, and I did a good job straining the oil, very small metal fragments and the magnet picked up a small amount of micro particulate metal. If you're correct then the real ugliness is at the bottom of the tranny housing and would be too heavy to drain out.

Per your post above, I agree, I wish my first post on Rennlist could have been more fun but your help can save me some time, money, and just headache trying to figure out what happened.

A clutch replacement is apparently one hell of a lot more involved than swaping in a used tranny so am hoping that will take care of things.

Any thoughts on locating a cheap but decent used tranny? I looked at Ebay and one sold yesterday with the LSD which would have been nice. Local Porsche yards (Parts Heaven and EASY) in Northern California are quoting $850 to $900 for a used one but think I can do better with some searching...perhaps here on Rennlist.

RMills944

I had the R&P go out on my 84, and when it happens you know it! The way mine felt was like you were running into a wall. The car suddenly stopped and would not move forward at all. This was due to the clutch plate letting the torque tube move and giving that much play to the back end, which locked up the Transaxle. Needless to say, it wasn't a cheap fix, but this doesn't sound like what you are describing at all. You would not have been able to drive the car off the road if it was the clutch plate if it did what mine did.

It sounds to me like the R&P stripped a few teeth. At least in my brother's truck we've stripped a few teeth and it would sort of lurch forward when the teeth caught, which sounds more like what you are describing.

Dave951M

If you have the rubber center clutch, I'd pull the starter to look for rubber chunks in the bellhousing before pulling the tranny. At this point, I'm leaning away from the r&p. That failure is pretty violent and sudden. Also, you might be losing a cv joint. I'd suggest pulling the starter first and looking for what seems to be tire chunks in the housing. If you see those, the rubber center clutch is nearly toast. Kinda FYI, I saw a car with similar symptoms, diagnosed by a wrench as r&p, that turned out to be the rubber clutch.

Stan944

quote of your symptoms:
"Car does not roll very well in neutral, rolls then locks up rear tires."

As the transmission input shaft is disconnected from the transmission output shaft in neutral, and the car locks the rear tires, it can NOT be bad clutch...