Weird things goin on...

[Sean]

After working on some miscellaneous stuff tonight, I went out and took my car for a drive.

Hunky dory...ladeeda...good good. I get to a parking lot, decide to do some doughnuts - did a few - got a few good laughs, then went to leave.

I floored my car in 2nd gear at about 2500 rpm. The clutch grabbed...but my revs bounced (back and forth) about 300-400 rpms around 3 times at the same time the car accelerated. Then the bouncing stopped, and the car accelerated smoothly.

It ONLY does this if I'm coasting along while in gear, and decide to floor it - as it, push the pedal to the floor instantly.

Not only do the revs bounce, but I hear a clunk in the back of the care. Before you tell me it's the flex disc - let me tell you it's not. EVERYTHING down there has less than 4000 miles on it. I DO however, have urethane subframe buishings - so am I maybe just feeling the vibration from my differential when I floor the car in the middle of a gear while coasting?

If I slowly give it gas and when maxing out in each gear (you know, accelerating as fast as my Super Eta will go) - I notice none of the above symptoms. My clutch is brand new, I have a Metric Mechanic lightweight flywheel paired with that. A fifth gear pull from 35-40 mph is strong - the clutch doesn't slip AT ALL.

So, really - the thing that bugs me the most is the bouncing of my revs when I floor the car. Really wish I knew what was causing that... :?

Suggestions, ideas...yea, that'd be great. :)

[Sean]

Still wondering what would cause the thunking in my rear end.

I've LOOKED at my differential bushing, and it looks fine.

Could it be that I used the longer bolts to put on my half-shafts? Maybe the bolts aren't tight enough? Maybe the bolts for my differential are not tight enough?

Another idea - does the flex disc only go on ONE way? I remember reading somewhere that some arrows need to line up. I didn't line anything up, so maybe this is causing some give?

Either way - I hear AND feel a pretty big clunk in the rear of the car when I floor it in any gear while coasting. if I floor it while already giving it gas, or pregressively getting more gas, it doesn't make any abnormal sounds.

Ideas please! I leave for colllege in a week, and need to get this figured out. :)


THANKS!

[AdamF 88iS]

There are arrows around the edge of the flex disc, they point to the flange.

[Digitalwave]

Yes, flex discs only go in one way. I have had a flex disc fail with less than 1,000 miles on it. Don't rule anything out.

EDIT: What I meant was there are a couple of ways you can improperly install the flex disc, but only one proper way.

[AndrewBird]

Did you ever think about maybe the diff being worn? If the ring gear and pinion are worn, they will have extra slop in them and clunk when accelerating. It's a pretty big problem on MG's but I've never heard of it on an e30 before.

[Addissimo]

Did you ever think about maybe the diff being worn? If the ring gear and pinion are worn, they will have extra slop in them and clunk when accelerating. It's a pretty big problem on MG's but I've never heard of it on an e30 before.

I know who you got the car from... that could be a good lead.
;)
-Addis

[Sean]

Well, it COULD be slop in the diff. Actually, that's probably waht it is. lol When it was out of the car, I tried turning it, and it did seem a little bit loose.

I'm still going to get down under the car and check that flex disc though, and make sure I got it on right.

I'll let you guys know what I come up with.


Thanks!

[nando]

I've had a clunk in my rear end somewhere for the last 35,000 miles, ever since I did the poly bushing swap. never was able to figure out where it came from, everything back there is tight. I'm thinking my u-joints are going bad..

[Digitalwave]

I've had a clunk in my rear end somewhere for the last 35,000 miles, ever since I did the poly bushing swap. never was able to figure out where it came from, everything back there is tight. I'm thinking my u-joints are going bad..

I've had it for a long time but it got worse after the poly bushings.

[modifiede30]

I've seen flex discs go out for many reasons, not preloading them, wrong direction, and driveshaft binding when installed. I'd look at yours carefully. I'd also look at your center support bearing to make sure its aligned properly, and that the rubber surround hasn't cracked or broken, since that would definitely cause a problem. Check your diff mount as well, to make sure the mount isn't cracked or the diff bushing isn't shot. I'd probably bet on the center support bearing based on what you've described.

[Sean]

CSB is BRAND new. had a new one put on at a driveline shop before I put everything back together.

I've looked at my flex disc, the diff mount, and all stuff I can see - everything is dang solid down there.

I personally just think it's give in my differential, which I feel due to the poly bushings.

So, I'm not going to fret over it. For having 214,000 miles on the engine and 183,000 on the diff, it's not doin too bad. :)