Another Drivetrain Slop Thread

[kdf8454]

So, I don't usually post here because I like to figure stuff out on my own, but I'm about to pull my hair out over this drivetrain slop I have. I'm looking for any additional input before I dive into the idea of replacing my trans completely...

Current symptoms:
-On/off throttle slop
-More apparent in low gears (all gears have this)
-Audible, but not insanely loud clunk in the center/rear of the car. Can be heard in cabin
-Fairly certain the slop is rotational in the driveline rather than a mount

Attempted solutions/Current aftermarket parts:
-034 Street density motor mounts
-2.8 transmission mounts with grade 8 hardware (nylock nuts)
-ECS poly rear diff mount
-Window welded rear diff brace bushings (not that they were cracked before anyway)
-034 center driveshaft support bearing
-Brand new replaced GKN driveshaft CV joints
-Fully refreshed rear axles (tear down, regrease, new boots)
-Apikol poly snub mount
-Recently rebuilt 1-2 collar and 1,2,3,4 synchros
-Replaced rear diff with another used unit
-Replaced center diff with another used unit
-Fresh Redline trans fluid
-Fresh Redline rear diff fluid

Even after all that, I'm still having this issue. It makes having a stage 3 car a bummer to drive when all you can think about is that clunk and how you can drive differently to avoid it

So, I'm at a point where I think it might be internal to the transmission for one reason or another. The slop was there before and after I rebuilt the collar/synchros. If anyone has any other suggestions I can try before pulling the engine yet again, I'd appreciate it. Hopefully this will help someone else down the road at some point

Car in question (save the "bags are stupid comments") since everyone likes pictures:

[S4inMN]

Did you forget to add DTS bar to your list or do you not have one?

[kdf8454]

Don't have one... I can go under the car and rotate the driveshaft back and forth a bit. Even without a dts bar I would think it shouldn't be this bad. Although I'm sure that would have some positive affect

[kdf8454]

I should also note that shifter movement is minimal

[Corradovolksb]

My guess is slop in your rear diff. You tightened up the drivetrain minus the DTS so the rear diff may have some slop. Do you get a clunk from the rear when on and off throttle?

[kdf8454]

What's the likelihood that I got another rear diff with the same slop? I replaced it with a used one (bottom of first post) and the center diff

[Tjtalan]

That's a hard one man, doesn't really have internet diagnosis potential. Time to take shit apart,

[kdf8454]

That's a hard one man, doesn't really have internet diagnosis potential. Time to take shit apart,

Yeaaa I know. I'm not looking forward to this again

[Wagonholic]

In for info.

Had an off-throttle clunk at low speed/low-rpm/low gear as well. Similar to OP. Suspected either rear diff mount or center driveshaft bearing.

Last year I noticed the mount on my DTS bar was cracked, so I replaced it with the energy suspension poly mount. helped a bit, but there is still slop. Mount is still in good condition.

Slowly started to get worse over the last several months.

Pulled motor/trans to do build. Checked driveshaft bearing. Perfect condition. Checked rear diff mount (apikol). Perfect condition. Checked motor mounts (RS4) and trans (new S4) mounts. Perfect condition.

Installing stern mounts before buttoning everything up. Also have 034 diff bushings as well waiting to go in. Interested to see what others have to say before reinstalling as it would be nice to get rid of this annoying clunk as well. lol

[marka4]

Hay I recently watched a youtube on 01e g box and saw the the input shaft works separately untill engaged is this on a clutch bearing like rc cars bell gear? Could that be were the issue is?

I hav never ripped apart a gearbox sorry if im rong,

[Bordom]

Lash settings could be off within the trans itself. Probably related to the input shaft somehow.

I would highly suspect center diff before going into all that. Perhaps have it rebuilt for 4:1?

Everything graciously mispelled by Android

[armageddon-]

It will be the rear diff and or front diff, I'm on the same boat, i will install a torsen rear diff. The stock diff has too much slack on gears.

[kdf8454]

Lash settings could be off within the trans itself. Probably related to the input shaft somehow.

I would highly suspect center diff before going into all that. Perhaps have it rebuilt for 4:1?

Everything graciously mispelled by Android

Maybe someone can chime in on how or where anything in the trans can be shimmed for lash. Or in the rear diff for that matter. Seems like this is a topic that has almost zero information out there. Without taking them to a specialty shop to diagnose something that might not be the root of the problem, it's hard to justify, but it might just come down to it.

Again, the center diff is something I've replaced with another used unit. Very unlikely that both have the same issue and nothing changed before/after.

It will be the rear diff and or front diff, I'm on the same boat, i will install a torsen rear diff. The stock diff has too much slack on gears.

There has to be some lash, but it should be a specified value and range from the factory. Both diff's I put in the car have more than I would like to see... maybe I need to post a video of turning the driveshaft back and forth with e-brake on/in gear.

[Scotty@Advanced]

Lash settings could be off within the trans itself. Probably related to the input shaft somehow.

I would highly suspect center diff before going into all that. Perhaps have it rebuilt for 4:1?

Everything graciously mispelled by Android

I've never seen a transmission that produced a clunk without a corresponding noise (while in gear or moving). It could be the pinion backlash, however for the gears to wear to a point where the lash is so great they slam into each other would mean something else went wrong with your trans.

There is no lash settings on the input shaft.

It's wager it's either the rear diff snout or the driveshaft. I've been seeing alot of the bearings just behind the rear diff input flange go bad due to low fluid in the rear diff.

The input shaft stops spinning when the clutch is disengaged.

[kdf8454]

I've never seen a transmission that produced a clunk without a corresponding noise (while in gear or moving). It could be the pinion backlash, however for the gears to wear to a point where the lash is so great they slam into each other would mean something else went wrong with your trans.

There is no lash settings on the input shaft.

It's wager it's either the rear diff snout or the driveshaft. I've been seeing alot of the bearings just behind the rear diff input flange go bad due to low fluid in the rear diff.

The input shaft stops spinning when the clutch is disengaged.

Well in that case, maybe I'll tear the original rear diff from the car down and see if anything looks odd. It has roughly 120k on it so nothing too major. It's also just sitting in my garage now (no better time to try I guess).

Scotty, do you stock that diff input flange bearing?

[MacDaddy]

Hows the u joint, also the flywheel (because its dual mass) and the clutch disc, those can all have excessive slop. I know you said its comming from centre/rear but sometimes noises can be deceiving.

[kdf8454]

Hows the u joint, also the flywheel (because its dual mass) and the clutch disc, those can all have excessive slop. I know you said its comming from centre/rear but sometimes noises can be deceiving.

Everything in the driveshaft itself feels solid. The center bearing support wasn't even that worn out (no tears, just soft), but I figured I would replace it since lots of people have problems with them.

Clutch is a Southbend stage 3 endurance with a steel single mass flywheel and about 25k on it.

I'm thinking the next step in this process is getting a baseline on rear diff backlash and pulling that apart.

[Monty23]

[armageddon-]

The problem wil be the backlash on diff gears, not crownwheel/pinion

[kdf8454]

That's kind of the approach I was going for more or less. But with my own tools and a "before/after" I mess with the internals. I'm assuming the SX shims are for locking components down.

Thanks for the bentley reference.

[armageddon-]

this...

[kdf8454]

IIRC there is little to no slop between the axle flanges themselves. It was mostly in the input flange - so pinion may be the source, but I'm not sure what is excessive. I'll check at some point this weekend and report what I find.

[armageddon-]

the slop you see at input flange is from the diff gear, the axle flanges will only turn what the cv-joint allow them to

if it was from crownwheel/pinion you would have a lot of noise/vibration

[Racin2redline]

i have nearly the same issue. all upgraded mounts apikol , im leaning towards rear diff issue

[WEBER]

Third me in! I'm also leaning towards diff, I hear it way back there. With no movement from the rear diff output flanges I can rotate the input flange about 5 degrees back and forth. Makes the same noise with my hand that I hear in the cabin.


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[Racin2redline]

Third me in! I'm also leaning towards diff, I hear it way back there. With no movement from the rear diff output flanges I can rotate the input flange about 5 degrees back and forth. Makes the same noise with my hand that I hear in the cabin.


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same. like when you lift off the throttle and accel sharply you can hear a metallic clank.

[Scotty@Advanced]

Well in that case, maybe I'll tear the original rear diff from the car down and see if anything looks odd. It has roughly 120k on it so nothing too major. It's also just sitting in my garage now (no better time to try I guess).

Scotty, do you stock that diff input flange bearing?

The flanges on the diff don't have bearings they ride against the diff carrier.

[kdf8454]

After spending way too much time trying to mold an rs4 bumper to my narrow body car, I finally got around to taking a video of the diff slop...

It is very possible that this amount of slop is expected. I don't really have the resources at my home garage to fixture things with nice dial indicators and such, so the video will have to do for now. Remember, I did already replace my diff with another used unit and the slop remains. The rotational play in the diff that came out of the car originally is very similar to the replacement that went in (not something I could check until it showed up at my door).

There is an audible clunk that seems to be coming from the splined section at the split joint of the pinion. There is minimal movement of the rear section itself, but it may appear that way because there's not a cv coupler to amplify it's affect.

Let me know what you think... I'm still not convinced

[kdf8454]

Anyone else have a rear diff kicking around they could check if it has similar lash at the driveshaft input?

[armageddon-]

ok, to bring this up top again...

In my spare diff I have the very same amount of lash/play between flanged shaft and pinion shaft as seen in the above video from kdf8454

The diff it self is fine(torsen), I just finished setting the backlash after new bearings. I will separate the flange housing from diff housing to check if is the sleeve, or the shafts splines have some wear.

[WEBER]

I'd like to know for sure, this is really the only thing keeping me from enjoying an otherwise very solid stg3 car.


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[kdf8454]

I guess I should have followed up on this...

I ended up swapping the trans to see if the source of the slop was somewhere in there (rebuilt trans found it's way into a D2 S8). Turns out, that was not the case - same exact result and a lot of wasted time. All spline 'slop' between the rear diff and center diff seem normal. At this point I've had 3 center diffs in my hands and they all had about the same mount of play.

What I did do was add a DTS bar and 034 track density trans mounts which made a pretty significant difference, but also added a lot of in cabin NVH. Something else I think may help is a smoother tune at very low throttle input (currently on deka 630s...)

Basically I've come to the conclusion that adding poly mounts/stiffer engine mounts eliminates the ability of the mount to absorb the normal amount of 'slop' that is required for proper component fitment. This may just be something I just have to deal with and try to reduce as much as possible (which the DTS bar has helped)

[slow ride]

I thought the same thing about the tuning at low throttle inputs as I noticed my slop a lot more right when going from a stage 2 type car/tune to my current stage 3 setup with EV 14 298 injectors. Basically need to slow the throttle action at those lower levels.

[BITRBO]

Exact same problem here. The noise isn't terrible or anything, it's just annoying so I've been reverting to louder music, which seems to be doing the trick ; )

Always figured it was the DS center support bearing as the noise seems to come from there, but it also sounds like its coming from behind the back seat under certain circumstances too. I have 034 rear diff bushings ready to install, but just haven't got around to it. I also have stiffer DTS bushing I can try, so maybe both will do the trick...

[armageddon-]

Ok, so, I took apart the diff cases, it took no effort to separate them at all, and no puller required to remove the sleeve, it should at least be necessary to remove the sleeve from the flanged shaft.

There is no rotation slack between flanged shaft and sleeve, but there is sleeve and pinion shaft.

So this is another factor contributing to the slack / clunck on our cars.

Now I think that I will just put some quicksteel putty or some kind of epoxy on the splines to remove the excess play or do you think that there is another cheap solution?

A video of the problem:

[killerkali]

My slack was a combination of the shitty 034 center bearing ( fell apart in less than 5k miles) and my rear diff had some incredible wear inside the gears. Tons of metal shavings inside the case, I think it happened due to low fluid and a lot of E-brake turns. Put a used diff and used driveshaft in, all is well now.