Shifter Vibration (Probably Tranny)

Kerry944 · 07-23-2003, 09:55 AM

I just replaced the lower exhaust bracket and rubber hanger at the rear of the CAT because it was making a nasty clanging noise at 3000-3300 rpm (The lower bracket was broken). I thought this might get rid of the vibration I'm feeling in my shifter, but it didn't. Any ideas?

Vibration only occurs between 3000-3300rpm.

bogomili · 07-23-2003, 10:04 AM

I have the same problem in an '86 951. I've timed that balance shafts (checked twice - even for incorrect gear indexing). I figured it was the torque tube.

Verruckt · 07-23-2003, 12:34 PM

Check your motor mounts. If they have failed it will lower the engine and mis-align the exaust. When mine failed the shifter was vibrating around 3000rps also.

85944na · 85944na's Garage

I've got new motor mounts, a new tranny, still have the vibration, my theory is it's the flywheel.

ronin · 07-23-2003, 11:18 PM

Ahaaa, I've had the same vibration in the driveline betw 3 and 4k (any gear) under strong acceleration. Didn't really consider the motor mounts. I think I'm going to try it though because the idle is just a tiny bit rough and I can't figure anything else to get it to smooth out.

I've also got some hellish clanking going on underneath the rear. But it pretty much sounds off all the time except for when I apply the brakes. I've looked underneath several times already and still can't figure out what the heck it is. Any suggestions?

arnebret · 07-24-2003, 06:43 AM

This is a problem that almost every 944 has. Some people never notice it, some people do.

I had this problem in an extreme version. I replaced the complete torque tube and in my case it was the bearing at the front of the driveshaft. My mech showed me that it was completly gone and the driveshaft became useless.

After the replacement i still had the vibration, but not audible anymore. But there still was a vibration in de gearstick at 3000rpm-3300rpm.

I discussed this problem with a lot of people in the porsche scene here and we came to the conclusion that (especially in the high-powered 944's) it's a bit of a design flaw. ALL the vibrations from the gearbox and torque tube are amplified by the long gear-arm that runs all the way to the tranny. At about 3000-3300rpm it will come to a point where resonation will arise. If your car's drivetrain is fully maintained, you shouldn't have this problem. But as time passes, things will wear out.

All vibration from the engine will run through the flyweel/clutch, and the long driveshaft. On top of the driveshaft, the long control arm for the tranny is mounted. All this vibration will be absorbed by the rubbers, mounts and stuff, but at the (in)famous 3000-3300 (the unstable point for the 944 engine) everything will resonate, especially under high load. Resulting in a shaky stick...

You just have to live with it, because replacing stuff will be like a lottery, you never know what the problem is. A bearing in the torquetube, motormounts, flywheel, controlarm, mountingpoints, balance shafts.... Good luck!

ronin · 07-24-2003, 10:04 AM

design flaw, eh? That's interesting. strange thing is though that I've had my car for nine years now and never noticed it until just recently when I was accelearting on a brand new, perfectly smooth stretch of freeway. Seems like the only way to cure it would be a total drive line rebuild.

arnebret · 07-24-2003, 10:19 AM

Well, by design flaw i mean: the construction will be fine after it left the factory and if well maintained will not result in any real problems. As i said, things WILL wear out, also in the driveline. Maybe they knew it might result in some vibration over the years and just couldn't help it (solution too expensive). My car is now 15 years old and has a slight vibration at the 3000-3300rpm, i'm happy with it. I know a lot more cars that vibrate that have front wheel drive and are just 5 years old, so...

ronin · 07-24-2003, 10:30 AM

ditto on the FWD with vibration, I rented a nearly new Sable (maybe 2500miles) last year and couldn't believe the vibration in the engine under acceleration with so few miles. It wasn't a normal type of vibration but definitely something that needed attention.

I guess it's a bit reassuring that the vibration I have seems to be common enough. I guess I'm not going to worry too much about it yet. Now if I could only figure out that infernal clanking at the rear of the car.

arnebret · 07-24-2003, 05:40 PM

Is the hatch closing right, and are both locks set so there's not too many play in it?
Maybe the spare tire? Oh, and if you have a sunroof, all the stuff like motors and so are back there as well. Just check it out...

Or did you mean a mechanical clunck?

carsontc · 07-24-2003, 05:55 PM

lots of this is cured with the correct Sachs clutch kit

or do you still have it even so?

85944na · 85944na's Garage

check the bolts on the cv joints, there are six on either side, connecting the axels to the transmission. I had a clanking and some bolts were loose.

bogomili · 07-25-2003, 01:32 AM

Well, this is not good news. Mine, though subtile, really bugs me.

ronin · 07-25-2003, 09:29 AM

Quote:

Originally posted by arnebret
Is the hatch closing right, and are both locks set so there's not too many play in it?
Maybe the spare tire? Oh, and if you have a sunroof, all the stuff like motors and so are back there as well. Just check it out...

Or did you mean a mechanical clunck?

A sort of large loose metal piece clanking sound coming from underneath the rear of the car. I had it up in the air already and couldn't find anything!?! The peculiar thing is that whenever I apply the brakes even slightly, it stops. I was thinking the other day that maybe the reason I couldn't find anything could be because whenever the car is up in the air and the suspension is hanging from its mounts, whatever is clanging around is either pulled tight somehow or whatever. I think I'm going to have another look this weekend.

260dlb · 07-25-2003, 06:19 PM

My 85.5 944 has "the vibration" in every gear in the mid 3000rpm range, and also an ocational clunk in the rear . the vibration I'm going to live with for now . Idid however find that the linkage on top of the transmision is worn , making the sift lever dance a jig.
As fsr as the clunk in the back I believe it is a worn transmision mount, again I think I'll hold off on that for now also.
Hopefully I'm on the right track with both problems.

arnebret · 07-26-2003, 05:11 AM

Maybe both things are actually the same problem. The clunking in the rear might come from a bad transmission mount. As i just stripped the complete rear of my car, and still can't find the clunk, i'm pretty sure it has to be something under the car. I was thinking about this: a bad transmission mount not only results in a clunk, but it might also reduce the dampening of any vibrations in the driveline. As i said: the engine is unstable at 3000-3300rpm, even the balanceshafts can't avoid this completly... the vibration will reach the transmission, where it should 'dissappear' in the mounts to avoid a bouncing gear stick. If these mounts have gone bad, it will result in a vibrating control arm where it is getting even worse resulting in a very bouncy stick...

Any comment would be great, as i think this might be something to really consider.

ronin · 07-26-2003, 10:05 AM

since we seem to be having similar problems, is your clunking a clunk or does it sound more like a clang? I know this sounds stupid but if it does turn out to be the same, we could save a lot of time solving the problem by doubling our efforts. Also, does your clunking seem to abate whenever you apply the brakes, either soft or hard?