phil0618

There is a weird clicking/ticking sound coming from the trans.

Trans is out of the car on the bench and when turning with a drill you can hear this regular clicking sound that is fairly loud and even louder in 5th.

My indie swears it's got to be on the output shaft just based on the speed and the fact that there is no noise when in neutral.

Anyone ever have this?

Might be in the market for a used transaxle depending on what he finds during dis assembly.

MB968

Couple of ideas from an old test engineer to maybe better id the problem. Any way you can spin it faster than with a drill. I'm assuming if you have a big enough drill to spin it, it won't be much over idle speed. I would expect most things to be fairly quiet at idle speed, but if ball bearings are just radial load bearings with some wear, you could conceivably get some noise from them under no-load conditions.

Also, can you use a strap or something to put a load on the output shaft. Or, two two by fours hinged with a v notch that goes around the output shaft, or?? Unloaded drivetrains can often rattle within the gear clearances, etc. Loading the drivetrain might help you better id the noise, and it might even go away.

Output shaft is probably not an unlikely source. I'd definitely try to check it for excess play to get a feeling for the condition of the bearings, and maybe even replace them if they are easy to get to.

Lastly, I don't know what a clutch type lsd might do if the clutch plates are completely worn out. You should run a test on the lsd to see if the torque transfer is within spec. I think I've seen info somewhere on how to test the lsd while in the transmission.

Good luck.

phil0618

Hi,
Thanks very much for the reply.

A couple of things.
First, the sound was first discovered in the car after getting the pinion bearing replaced. I think the clicking sound might have always been there, but masked by the whine of the bearing. However, there is no way to really know that.

The sound while testing on the bench with the drill is plenty loud. No difficulty hearing it even over the sound of the drill. It seems loudest in 5th gear and that was true when we had the trans in the car and on the lift. It seems to be more prominent near where the axles would attach to the trans. Is that where the LSD is located? The LSD is not something we had considered so that is an interesting thought. Also, any thoughts on why the ticking would vary greatly in sound in 5th gear? That's not to say that it can't be heard in other gears - it absolutely can, but it seems noticeably louder in 5th.

Thanks again,
Phil

MB968

I don't really thing it is the lsd. If the clutch plates and differential are working properly, when you spin it with the drill, the differential won't even be working as both right and left side outputs will be the same speed. The input rpm of the ring gear will be the same as both right and left outputs.

The drive shafts for the rear wheels do connect to the output of the lsd. The clicking doesn't seem like a noise I'd expect from the lsd. But, you can make sure the clutch plates are still working by testing per the manual to rule this out.

A click isn't exactly the type of noise you'd expect from the drivetrain. It may take disassembling it to find the cause. But, as I noted above, you could do some things while it is still assembled to have a little more info that could help you find the cause.

Don't know why 5th would be any worse. It is an overdrive gear (output rpm higher than input rpm). But, I think 4th, 5th, and 6th are all overdrive gears. It could be that something about the shift linkage position in 5th that is causing the clicking.

If it is an obvious bearing, or something else, your mechanic may find it easily. But, if it isn't obvious, I'd get it to a shop that has a lot of experience with the 968. If not obvious, it could be tricky to find.

phil0618

Here is an update and will provide another when things are finally sorted.

After removing the gear set from the differential case I can still hear the noise ruling out differential, ring/pinion, as well as the large pinion bearing.

In fact I can rotate the output shaft by hand and feel a specific point at which it binds slightly. Marked a tooth on the shaft and I can find this exact spot blind every time. I can visually see no issues with 1st through 4th or reverse. Here's where it gets interesting - I can't get the back case for 5th and 6th off without an internal bearing puller. I did however loosen all the rear case bolts and low and behold the drag disappeared. Tightened back up and it was right back.

968workaholic

When you put these gearboxes back together, and the gears are not in the EXACT place as they were before, the sides of the gears rub against one another and make a ticking sound. Even after measuring the gear distances on the shaft upon disassembly and putting them back to that distance, I still get some noise from time to time. After about 500 miles, the normal break-in period for a trans rebuild, the noise is gone. Not sure why but that's how it works. Don't drive yourself crazy over it unless it gets worse

phil0618

The clicking in my case was really bad. With the car on the lift and in gear it was scary sounding. Not something that seemed like it would be solved by break in.

So, the transaxle was taken apart and it was discovered that 6th gear was slightly deformed. One tooth in particular. You could not see it with the naked eye, but if you manually rotated the shaft you could tell it was 'catching' in one spot. The noise got dramatically less after gently filing the edge of the gear down so that it was more uniform. However, this did not completely eliminate the noise so we purchased another 6th gear and that seems to have solved the problem.

Car is back together and running great...

A painful experience, but it seems to be behind me.