Random bang from drivetrain at speed?

Hello,

So, got a '98 4.0L with the AW4. A couple weeks ago, noticed at highway speeds that I'm getting a random bang-type feeling or sound from either the transmission or the rear differential. Rear diff was upgraded with an aftermarket limited slip unit about a year or two ago. This has performed flawlessly so far. Anyway, the bang began occurring while driving at 55-60mph, and at low rpm's, around 1500, when it begins to bog down while starting a climb up a hill or similar.

Lately, the bang has occurred more frequently, at lower speeds like 35mph, and on level ground, however with the low rpm's and bogged engine situation like when accelerating if traffic speed increases ahead of me.

I suspect something seizing or binding, either in the transmission, or in the limited slip. Maybe friction modifier (or lack thereof) in the fluid is causing problems?

Anyway, just looking for folks who've had a similar problem and what their experience was.

Thanks!

Chris

Pop the cover on your diff and check for debris. Your Limit Slip may have parted itself for the worst case, or you may simply need to replace the diff fluid AND the Limit Slip additive for the best case.

Yes, the additive is important!

My factory Limit Slip produced the same symptoms over time. When I went to change the fluid, the discs were in pieces. I replaced the limit slip with a Detroit Trac Lock.....

Yup, checking the limited slip will be the first step. It's got a Detroit True-Trac in it. I just read over the FAQ's over there and they say no additive is required. I wanna say we just put 75-140 fluid in it when the limited slip was installed. And it's done well for the year or two it's been in the vehicle. So we'll see.

No additive and non synthetic fluid for the TT.

Talyn said:

No additive and non synthetic fluid for the TT.

Click to expand...

True... but if the OP has a disc type (stock) limit slip, then the additive is required.

My error in terms above. Should have read:
Stock (Trac Loc) or Auburn = disc type limit slip (needs additive)
Detroit = Tru Trac (no additive)

Just read your limit slip manual, to determine what you need...

He said he has a true trac

Just for added clarification, The Auburn type limited slip is a cone style, not a clutch/disc plate type. It still needs the modifier like the clutch type though.

Regardless of the type, if it had the wrong fluid I would think it would have started making noise long before this. It's been in the vehicle a solid year, if not more.

I don't have the money to get it into a shop to be looked at, and the apartment complex I'm renting at currently doesn't allow tenants to work on their stuff. I've decided to drive it as little as possible until we're able to move into our new house this fall.

Anybody else has ideas, keep 'em comin', though. Thank you!