Possible Diff issues

[Kreiger]

So, for a month or two now I've heard a loud clunk after half throttle or more acceleration or burnouts, thinking it was my motor mount, I didn't even consider checking my trans or diff fluid. Recently I've been experiencing that I can do one burnout, but come to the second, the car just simply doesn't want any of it anymore and floats at about 2k rpm even at full throttle during a brakestand.

Finally today, something gave out after a burnout, following said burnout I heard a very loud clunking sound, followed by jerking and then the car not getting into gear in 2nd mode and finally engaging in drive at about 2.5k rpm, but shifting perfectly fine through all the gears afterwards and made it home without any issue??? Now I haven't pulled any fluids yet and I'm hoping its my diff, but I got it up on a jack and checked if there was any play in movement axle to axle manually spinning them with the car in neutral and it seemed like the axles engage eachother with almost an inch of play between themselves, clunk upon finally contacting the gears in the diff and slightly jerk the driveshaft when doing so.

My shift linkage on the transmission seems to be ok, but I've never seen what one should feel like normally, so maybe that's messed up?

Car has 200k and is a 98' 740i pre-TU, any help will be greatly appreciated

[Timm]

You have frizzled one of the clutch packs in your transmission - the point where the revs were hanging at 2k and your wheels were not spinning was one of the clutches slipping, and just like a clutch on a manual car that kills them!

[Kreiger]

You have frizzled one of the clutch packs in your transmission - the point where the revs were hanging at 2k and your wheels were not spinning was one of the clutches slipping, and just like a clutch on a manual car that kills them!

What can I do to remedy this, just flush the fluid and hope for the best? or what? Because now it seems fine, and does this also explain the unholy clunking and everything else I heard following this?

[Timm]

It is certainly worth changing the fluids and filter if all is going OK at the moment. The clunk could be any number of things - driveshaft or mounts seem the most likely.

[Kreiger]

It is certainly worth changing the fluids and filter if all is going OK at the moment. The clunk could be any number of things - driveshaft or mounts seem the most likely.

I know for a fact my passenger engine mount is completely shot, so I need to go for that next, I already ordered a 3.15 sport diff so I suppose that's gonna go in anyways, surprisingly all my driveshaft mounts are completely intact, so it can't be that, possibly the diff mounts? Are the horrid clunks possibly just from the roasted clutch engaging violently and throwing the drivetrain around on the destroyed mounts and finally, am I going to have a slipping transmission that is just on it's way out that I'll have to eventually replace even if I change the fluid?

[TheAngryBear]

Time will tell on the transmission. Maybe you lucked out and all is well...
Change the fluid and see what it is like.
The easiest way to preserve the trans though... is to lighten up on the burnouts.


2001 750iL DD74441
E65 fan & clutch, E65 headrests, Front First Aid Kit, Ultimate Cup holder

2005 X5 4.8is LE82680
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[Kreiger]

How long you think she's got before the trans gives out? I'm planning on doing a manual swap anyways so I guess this is just more motivation to do so... anyone have some helpful links for swapping?

[acspecialists]

Go for an S62 manual swap! Your trans is on its last legs, if Timm says a band is gone its gone.

[racer2086]

Incredible the unnecessary abuse people put their cars through. Your transmission is dying and if you change the fluid, it very well could be game over. Change fluid at your own risk. Unfortunately, the fluid is probably a burned mess with all the burnouts.

The clunking could be a million things from transmission mounts to CSB to rear CV to internal transmission problems. With 200k and burnouts, I wouldn't be surprised if all rubber mounts that were aged are torn now, including the rear subframe mounts.

[MrChrysler]

Nice job. Usually when transmission doesn't lock in properly anymore even a slightest slip will make it last couple of hours maximum.

In normal operation it's quiet difficult to kill this tranny unless you had too little transmission fluid or you have badly overheated it.