Drivetrain shudder

[papak]

I have noticed that in the lower gears (2nd, 3rd particularly), as I approach max torque (3500-4000 rpm), I sometimes experience a shuddering in the drivetrain that seems unrelated to engine function. At first, I presumed this was related to the incomplete tuning of the ECU functions but now that I have been running close sloop for a while, the problem is still evident. It is as if the friction plate springs are becoming heavily loaded and start to “fight back” as it were. A simple feathering of the clutch seems to resolve the problem momentarily.

 

I am running an Exedy organic clutch and pressure plate on a lightened Exedy flywheel, all designed for a Ford Focus. While I plan on contacting Exedy today, have any others experienced this sort of problem? When I recently had the drivetrain apart to rebuild the transmission, the clutch components looked perfect. Both the flywheel and friction disk were perfectly flat with no discoloring. The springs showed no wear on the ends. The splines were fine.

[ashyers]

papak,

I wonder if the clutch is slipping? Does it ever flare when you are at WOT and the torque peak? Is it possible the friction material has been contaminated?

 

I'd check the d-shaft, U-joints, and d-shaft hardware just to be safe.

 

Of course, maybe it's tire spin !

 

Edit: Was everything was fine prior to pulling out the gearbox?

 

Andy

Edited August 18, 2020 by ashyers

[papak]

It only occurs when the drivetrain is “loaded”, as in accelerating through a turn in second or third. The drivetrain is perfectly intact. No clutch slip or tire spin. I’ve experienced the event since initial assembly. The diff is a new Suretrac in an R160. The cv’s are perfect.

[Dave W]

I had the same type of issue with the drivetrain after pulling the engine/trans. One of the mounts ended up being pre-loaded, after re-assembly. Try loosing both engine mounts and trans mount. Then physically move the power train back and forth plus run the engine up and down the rev range. Tighten every thing back down and take a test drive. Dave W

[papak]

Thanks. I’ll give it a try. I’ve tried everything else.

[papak]

I have reached out to Exedy USA for suggestions. They make some reference to this possibility in that they list a similar style but higher capacity clutch plate as an option.

[ashyers]

papak,

You mentioned that it happens when accelerating out of a turn. Not when going straight? If so I'd be inclined to look at the limited slip. Is it possible you're getting some kind of stick/slip/stick/slip going on? I seem to recall you did a diff recently.

 

Andy

[papak]

It does occasionally occur in a straight line, usually upon accelerating after holding a constant speed in 2nd or 3rd. Probably not the LSD as this is the second LSD in the car. It seems to be correlated to the presumed peak torque, around 3500-4000 rpm.