Backlash in the Transaxle?

[DoctorDex]

Originally Posted by keithmac

If you can rotate the prop shaft 1/6th of a turn (near the rear diff) the backlash must be a mile out of spec? or the rear diff`s worn out. I can turn mine 1/8th and that`s enough for a clunk from the back.

The limit`s 5mm on the diff casing (see link), that`s probably 1/16th rotation or less!

I phoned the dealer and I had the read the old work order back to me. It says they adjusted the rear differential backlash from 8mm to 3mm. They source the cause of my backlash to be the transaxle, as the backlash measured @ the output shaft is grossly out of spec.

Does anybody know the causes of backlash in the transaxle?

Declan

[maddog]

either horribly worn gears, os wear, vcu/center diff slop, clutch spline slop, clutch friction plate issues, or bad bearings off the top of my head

have fun

[KORMEX]

Originally Posted by DoctorDex

The clunk I'm experiencing is noticeable in all gears, but it is more pronounced in 2nd and 5th. I notice it especially when I'm accelerating quickly in 2nd and then I let off the gas suddenly. The car will literally jerk back and forth and my head bobs like bobblehead doll. This also happens in 1st gear, in the lower rpms range, which makes driving around parking lots tonnes of fun... The only way to soften the clunk and make it less noticeable is to slip the clutch when shifting into every gear, and to push in the clutch every time I want to decelerate and to slip the clutch back into gear.

So, just to clarify things here. You don't think the fact that I'm able to turn my propeller shaft 1/6 of a turn is significant/the cause of my problem and you think it has to do with my transaxle? If it is the transaxle, what components could be causing the clunk? I just finished replacing my OS and VCU and this made little to no difference.

Thanks again.

Declan

I did see where you mentioned the 1/6 turn on the shaft , but if you say the mechanic adjusted it ,I assume then that thats not the problem. 1/6 (60degrees) is alot, but then how did you measure ?

As Maddog mentioned there are many things that would cause play in the transaxle , but I'm assuming that the ovious was looked at when replacing the shaft and VCU .

When was the last time that the clutch disk was looked at ?
It can also be missing springs , I though about this when you mentioned parking lot driving .

You see how hard it is to try and troubleshoot remotely ?

anyway if you take it as a challange to fix this I will help as much as I can .

Frank

[DoctorDex]

I understand it is very difficult to troubleshoot things remotely and I appreciate all of your help.

As far as the propeller shaft play is concerned, I have to admit I didn't actually measure it, it was more of a rough estimate on my part. To me, it feels more than 3mm, but at the moment, I don't have a jack and stands handy to verify it.

Concerning the transaxle, I just finishied installing a new 300m output shaft, a new VCU (the old VCU was bad) and a new planetary gear assembly. There is 2mm of slop that comes from the new planetary gear assembly dowel pins sitting loosely in the new VCU, but I've come to the realization that I'm just going to have to live with this, because the new parts had the same amount of slop as my old parts.

Regarding the clutch, I installed a brand new clutch (centerforce DF) back in June. At this time, I checked the clutch splines/input shaft splines and they looked good and the clutch was a very tight fit. Since this time I haven't been able to really abuse my car, because I've been breaking in the new clutch and trying to track down the cause of this clunking. Personally, I can't see it being the clutch, as I had this problem when I was still running the OEM clutch.

As far as the gears are concerned, I took a quick peak at them when I had the center diff. apart and my _untrained_ eye could see nothing amiss. This definitely does not rule out worn gears, but with that being said, I've been led to believe that our synchros are the weakest point in our transaxle and you'd think they'd wear out before the gears would (mine are still in great shape)??

This leaves me with bad bearings and/or a bad center differential carrier, or do you guys have anything else to check or add to the list?

The thing that I can't figure out is, why does the clunk not occur if push down on the clutch while in decel and then slip the clutch back into gear (while giving it throttle) to accel.?

Thanks again.

Declan

[cbehnken]

I wouldn't trust the dealer saying the driveshaft is good as gospel. I think it was Bret Brinkman who had a bad shaft that would only cause problems under heavy load. It could not be shown faulty testing it on a bench.

[mikes2nd]

anyone mention motor mounts? ill bet those are shot also.

and yes get a pst one piece cf driveshaft also or 2 piece if your vibration paranoid.

[maddog]

Bret problem was the rubber wore out on the 2 pieces of driveshaft so they started to slip inside each other. this would not cause the slop he is talking about

[DoctorDex]

I'm not sure if this is of significance or not, but a few months ago I had a datalog of the clunk. I was accelerating in 2nd up until about 6k and then I let off the gas suddenly (because a cop came out of nowhere). This caused the clunk with the violent jerking back and forth and on the log this came up as fluctuating timing. If I remember correctly, 15 degrees of timing was pulled, for a split second and then it went back to normal. Is normal for a car that is decelerating?

Declan

[DoctorDex]

Originally Posted by mikes2nd

anyone mention motor mounts? ill bet those are shot also.

I visually checked the motor mounts when I had the car apart to change the clutch (back in June). In and around May, I also tested the motor mounts, by putting it into 1st gear and hitting the gas with the brakes on. I've been told that bad motor mounts should show themselves (to an observer) with this test.

As far as the CF driveshaft is concerned, if I had the money to burn, I'd buy one. However, I don't want to go and replace everything in my driveline/drivetrain only to find out that it was something else and still be stuck with the same problem.

Declan

[KORMEX]

Originally Posted by DoctorDex

I understand it is very difficult to troubleshoot things remotely and I appreciate all of your help.

As far as the propeller shaft play is concerned, I have to admit I didn't actually measure it, it was more of a rough estimate on my part. To me, it feels more than 3mm, but at the moment, I don't have a jack and stands handy to verify it.

Concerning the transaxle, I just finishied installing a new 300m output shaft, a new VCU (the old VCU was bad) and a new planetary gear assembly. There is 2mm of slop that comes from the new planetary gear assembly dowel pins sitting loosely in the new VCU, but I've come to the realization that I'm just going to have to live with this, because the new parts had the same amount of slop as my old parts.

Regarding the clutch, I installed a brand new clutch (centerforce DF) back in June. At this time, I checked the clutch splines/input shaft splines and they looked good and the clutch was a very tight fit. Since this time I haven't been able to really abuse my car, because I've been breaking in the new clutch and trying to track down the cause of this clunking. Personally, I can't see it being the clutch, as I had this problem when I was still running the OEM clutch.

As far as the gears are concerned, I took a quick peak at them when I had the center diff. apart and my _untrained_ eye could see nothing amiss. This definitely does not rule out worn gears, but with that being said, I've been led to believe that our synchros are the weakest point in our transaxle and you'd think they'd wear out before the gears would (mine are still in great shape)??

This leaves me with bad bearings and/or a bad center differential carrier, or do you guys have anything else to check or add to the list?

The thing that I can't figure out is, why does the clunk not occur if push down on the clutch while in decel and then slip the clutch back into gear (while giving it throttle) to accel.?

Thanks again.

Declan

Yea there's not much you can do for the VCU planetary coupling ,its part of the design.

Bearings or gears would have other Symptoms

I would still have you check the front drive axles for slop in the front carrier assembly.