Drivetrain experts please help! Too much play...

bigchillcar · bigchillcar's Garage

Guys, I've done searches tonight until my eyes are watering and I'm just stuck on this one. Here's the symptom: If I jack up the rear of the car so the wheels are off of the ground, put the car in 4th gear and go to rotate the wheels, I can feel a lot of play before hitting 'resistance' and feeling the transmission turning.

I can feel this effect while driving by just tapping the gas while rolling along in a low gear...I can make this free play sort of 'clunk' by doing so. I've had it suggested this could be motor/tranny mounts, but I don't see how. My mounts look and feel fine, besides if I can feel the play with the car jacked up, how could it be mounts?

I thought for a while it was a cv joint issue. I've had problems with u-joints in jeeps in the past that resulted in symptoms like mine, so I thought maybe cv joints could act likewise. Consensus seems to be these shouldn't be the cause. Anyway, my cv boots are nice and intact and I don't hear the clicking I've heard that failing ones should make.

I tend to believe that the problem lies inside the tranny, whatever the drive shafts are contacting inside to turn the tranny must have too much free play. Can anyone help?
Ryan

cstreit · cstreit's Garage

Try moving the axles up and down vertically. There should be virtually no play. However I recall being able to move mine several inches of rotation before getting resistance.. THis may be normal

Early_S_Man · 08-10-2003, 08:22 AM

Ryan,

How long has it been since you removed, cleaned, and repacked your CV-joints, if ever???

The play you describe is normal, but freshly-repacked CV's wouldn't make the same noise as 'dry' ones!

bigchillcar · bigchillcar's Garage

I haven't ever done the maintenance you've described. And although I agree that there is supposed to be some play felt when the wheels are rotated, I think mine is excessive as I can feel it too easily when driving at low speeds. The sensation is very reminiscent of sloppy u-joints.

There seems to be some debate as to whether this symptom could be caused by worn cv joints or not. Would worn bearings in the cv joints produce the slack i've described? I kind of hope that this is the cause; this job is within my present capabilities. But what might cause this from within the transmission? It doesn't seem that this is going to be an easy diagnosis over the board. Sounds like I'm going to need to get a mechanic's opinion.
Ryan

cstreit · cstreit's Garage

Ryan...

Before you spend money, check the CV's...

I check the play up and down. Pull back the boots and see if there is a LOT of grease in them...

RoninLB · 08-10-2003, 11:51 AM

Quote:

Originally posted by cstreit

I check the play up and down. Pull back the boots and see if there is a LOT of grease in them...

and I also lock the wheel and twist the axle side.. I usually change them at about 1/4in indivudal CV twist.. same twist routine for tranny CV.. I'm not a pro for diagnosis of the foreward/rear play.. it's just what I do. and I also use this giant off road machinery Mobil CV grease........Ron

bigchillcar · bigchillcar's Garage

My axles don't have any rotational play which leads me to think that maybe they're okay. I can go back and forth between the wheel and the tranny with the axle, there is movement there which I believe I understand is normal. It really feels like the slop is with whatever the axle is in direct contact with inside the tranny.
Ryan

Early_S_Man · 08-10-2003, 12:42 PM

Ryan,

A high-quality moly grease is critical to long, quiet CV-joint life! I've used SWEPCO 101 in the past with excellent results, but recently switched to Valvoline's #985 or #986 SynPower Synthetic Grease with Moly!!!

Here are a couple of very good articles about servicing Cv-joints ... with some excellent pics of what to look for in the way of damage:

http://www.type2.com/bartnik/cvjoints.htm

http://volksweb.relitech.com/cvjoints.htm

And ... here are the 'old' air-cooled VW Bentley pages with all of the Lobro instructions for disassembly, etc. ...

beepbeep · 08-10-2003, 12:58 PM

almost certain it's CV's. My 930 did exaclty the same untill i changed all CV's. After that i could drive @ 800 RPM and no bucking...

bigchillcar · bigchillcar's Garage

Warren,
Muchisimas gracias for the pic...it's on my desktop awaiting printing.

beepbeep,
sounds like you had my symptoms alright...a little buck when tapping the gas, feeling like drivetrain slack. I'm still having trouble visualizing how the cv's account for this particular slack, but I suppose it will become apparent when I tear into them.
Ryan

beepbeep · 08-10-2003, 02:34 PM

yeah, don't know how they acount for the slack, I just know that it did buck a lot when i drove slowly at very low revs, then took it to the dealer and mech said "bad CV's" and they changed them all and voila, no slack or bucking.

350HP930 · 08-10-2003, 02:40 PM

A clutch disk can also contribute to drivetrain slack.

As the dampner springs in center sections get old and compressed the will allow a noticible amount of rotation.

Don't even get me started on the clutch disks with the rubber center instead of springs. What the hell was porsche thinking when they put those things into the 930 and other models?