Something serious broke, 86' 944 n/a, ideas?

LowTechRedneck · 03-03-2011, 04:19 PM

I have an 86’ 944 n/a that had something go seriously wrong in the driveline today.

It started out simple enough, while driving I noticed an odd noise coming from the back end of the car. It sounded like a cross between the metallic rattle of a loose heat shield, and the “popping” sound of exhaust leaking around a bad gasket. So I naturally assumed I had an exhaust leak

When I got to where I was going, I tested the exhaust, and found it was not loose. I started the car, let it idle, and manually worked the throttle, I could not duplicate the noise. Checked to see if I was dragging anything from the underside, nothing showed.

On the return trip however, the noise once again reappeared. I took note of the conditions and found that it was loudest at low speed (20-30 mph) and louder under throttle (it all but went away during coasting). It seemed to be dependant on engine RPM, as braking/steering/speed didn’t effect the frequency, but pretty much constantly there, the only way to make it “go away” was to go up to freeway speed where the wind and road noise would drown it out.

I noticed no other problems, no wheel noise, no tire noise, no handling issues, no leaks and no warning gauges.

Anyway, about an hour later, I came up to a red light. When the light changed, I let the clutch out and the car moved forward about 2 feet and then the rear wheels locked up hard, hard enough that it stalled out the motor. After restarting, I was able to limp off the road, but only by “brute forcing” it, the wheels would turn about half a revolution and then apparently lock up because the car would “hop” a bit accompanied by a loud thunk each time, freeing the wheel for another half-rotation before it would happen again. Once off the road, I noted that with the car in “N” and the E-brake off, it would not roll downhill, also, I checked to see if anything had obviously “blown up” underneath, but saw no leaks or obvious mechanical damage.

I had the car towed home, and now am wondering where to start troubleshooting what went wrong. As far as I know this is it’s original transmission (5 speed, but I don’t know if it has LSD or not) and the car itself has been problem-free for the last 5 years with the only needs being the usual filters/fluids. The clutch is newish, it was replaced when I bought it and due to a short commute, I only put about 5K on the car a year.

Any ideas on what happened and where to start looking? Did I mash up my gearbox somehow? Because that’s what it sounds like. Any help would be appreciated. Mileage at the time of the incident is 181K. More details available upon request.

John_AZ · 03-03-2011, 04:42 PM

1. CV bolts backed out
2. Rear wheel bearing or Rear wheel nut loose.
3. R & P chewed up

Go under the rear and check the CV bolts.

GL
John

SolReaver · 03-03-2011, 05:42 PM

CV bolts. let us know what you find when you jack it up and take za look.

AKCJ · 03-03-2011, 05:45 PM

I would normally say CV bolts but I'm not sure if that could somehow make it "lock up" where it's hard to move.

So, that leaves wheel bearing, R & P, or parking brake failure. The parking brake uses (small, light weight, old) brake shoes inside the hub area. If something came loose it could cause the noise and the lock up condition.

Let us know when you find it.

ernie9944 · ernie9944's Garage

Sound like a gear or ring pinion (hope not) GL.

Rasta Monsta · Rasta Monsta's Garage

Busted CV.

LowTechRedneck · 06:32 PM

I'll get started this weekend, let you know what I find. From a cursory look, I didn't notice any CV damage, at least not on the outside. But those are probably the factory CV/axle assemblies too. Though I did check the seals and put in new grease when I had them apart a few years ago (to do the aforementioned clutch)

HondaDustR · 03-03-2011, 06:36 PM

What you described was exactly what it was like when the final drive ring and pinion took a crap in mine a couple years ago. Just pop, clunk, clunk, skid to a halt. After looking under to see that the drive axles were still there and attached, the drivetrain would "bounce" off of itself against a very hard jam that was able to be muscled through with alot of very horrible noises. These transmissions are known to fail this way. Worst part was it did it out of nowhere all of the sudden just pulling out of a parking lot. I didn't even have the fun of failing catastrophicly doing a killer burnout or anything. Not that I ever would, but if it's going to break anyway...

Sorry to hear it!

John_AZ · 03-03-2011, 08:19 PM

Nice video HDR!

...Redneck,

In the video the inspection plate, passenger side of the transaxle was taken off.

If you find nothing else wrong from previous suggestions, drain the transaxle fluid in a bucket with a rag over the top. Panty hose works. You may see slivers of metal. You might want to reuse the fluid if nothing is wrong.

If you want to go further, Remove the passenger side CV and axle.....Inside the transaxle hub is another bolt to remove and the hub will pull out.

Remove the 12? bolts around the inspection plate and pop it off.

With any luck, you will not see what HondaDustR had in his video.

GL
John

Jrboulder · 03-03-2011, 09:15 PM

I just threw up a little in my mouth.

Oh, I have a spare. No worries!

Jackson

wild man · 03-05-2011, 05:53 PM

Unfortunately, my confidence level is extremely high that it IS in fact, the R&P Good thing youv'e got yourself a spare.

Pete R · Pete R's Garage

worst pics and vid EVER HDR.. it will take me an extra hour to fall asleep

Now did that junk the case and everything? or could you replace the R&P?

matthewb · 03-05-2011, 10:05 PM

Quote:

Originally Posted by John_AZ

Remove the 12? bolts around the inspection plate and pop it off.

I am pretty sure its 9 bolts

Wild man... I dont think it was the original poster who said he had a spare.

pete... N/a transmission are so cheap its not worth rebuilding after something like that. Bearings for the rebuild alone will cost twice as much as a used transmission then unless you know what you are doing its not going to last anyway. Then he would need to come up with a R&P...

That being said, I have a N/A ring and pinion if you need on.

Matt

wild man · 03-06-2011, 06:38 AM

My bad! I sincerely apologize to OP on that one. That being said, I have a nice N/A transaxle (out of a 87 924 - still in actually) in perfect condition (88K) if you need on(e).

Pete R · Pete R's Garage

Quote:

Originally Posted by matthewb

I am pretty sure its 9 bolts

Wild man... I dont think it was the original poster who said he had a spare.

pete... N/a transmission are so cheap its not worth rebuilding after something like that. Bearings for the rebuild alone will cost twice as much as a used transmission then unless you know what you are doing its not going to last anyway. Then he would need to come up with a R&P...

That being said, I have a N/A ring and pinion if you need on.

Matt

I have that AOR (or whatever it's called) tranny.. so we'll see what happens, It's good now.

HondaDustR · 10:26 PM

Quote:

Originally Posted by wild man

My bad! I sincerely apologize to OP on that one. That being said, I have a nice N/A transaxle (out of a 87 924 - still in actually) in perfect condition (88K) if you need on(e).

If it is the transmission, jump on this deal ASAP. The 924S transmissions have the short 5th gear that makes the car very good on the highway and for spirited driving. If fuel economy is your main concern, it's not the best choice, but I still get a decent 25-27 mpg on the highway for ~3000 rpm at 60 mph...right in the sweet spot of the torque curve.

Quote:

Originally Posted by Pete R

worst pics and vid EVER HDR.. it will take me an extra hour to fall asleep

Now did that junk the case and everything? or could you replace the R&P?

Think the pics are bad? You should have heard the noises when it let go! And the noises it made limping through the intersection it died in front of. The case appeared to be fine and it was all sold for parts. It is possible to replace the R&P, but there's alot of press fit stuff, bearings that would need to be replaced, and even worse, the new R&P would need to be correctly shimmed. The workshop manual diagram for that makes heads spin. A good used NA transmission costs around $500 shipped. A R&P set alone is something like twice that.

I don't know if it was dumb luck or good fortune, but the night before I was driving home from NJ at 1 am. After the fact I really was pretty ok with it dying when it did.

weglarz944 · weglarz944's Garage

I had the same exact thing happen to mine a few weeks ago leaving the starting line of an autocross, lots of people to witness the carnage. I will be in the market for another transaxle in a week or two i think. Anyone know of any reasonable (i.e. not thousands of dollars) upgrades to keep it from happening again? Any reason to think the 968 transaxles have stronger pinion gears/ can they be gotten for a reasonable price?

FrenchToast · 08:06 PM

Quote:

Originally Posted by weglarz944

I had the same exact thing happen to mine a few weeks ago leaving the starting line of an autocross, lots of people to witness the carnage. I will be in the market for another transaxle in a week or two i think. Anyone know of any reasonable (i.e. not thousands of dollars) upgrades to keep it from happening again? Any reason to think the 968 transaxles have stronger pinion gears/ can they be gotten for a reasonable price?

The N/A trans is fine for N/A power and even a little more. The N/A trans starts to be stressed probably at about 250 ft/lbs or 250 hp. The Turbo transmissions are good for about 400hp or so I think.

However few Porsche transmissions like to be launched. So if you launch the car a lot, it will break the R&P.

The gearing is all different for the 968 box, not to mention another gear. Out of the entire 924-44-68 series, the 968 transmission is the strongest of the manual transmissions.

951 AOR transmissions have hardened 1st and 2nd gears, as well as a cooler. FWIW. But the turbo gears are much taller.

Take care,