ZF-6 noise on the freeway

[Skant]

(Yeah, I know I was just touting how nice the ZF6 is... it's nice when it's working right. But mine is having an issue right now...)

I just recently switched to a 4.11 rear end, and I think it may have exposed a bearing going bad in my transmission.

A warbling whine starts somewhere between 65mph and 70mph. Seems to be coming from the rear of the tranny. It's pitch is directly connected to road speed (not engine speed). It tends to quiet down or even go away under acceleration or deceleration. It gets quite loud at cruise.

It may actually be going away on its own... it seems like the symptoms have gotten less as the new rear end has gotten more miles on it. But I dunno. It probably shouldn't have provoked a noise in the first place, so it's an indication that something is wrong.

I'm not a mechanic, but it sounds like a bearing going out to me. It's sound is similar to when the bearings are going out on a computer power supply fan.

Are we talking about transmission rebuild time here? ($$$$!!!!) The car has 50k miles on it. Could this reasonably be a case where just the bearings on the output shaft could be replaced or something? Or is this maybe not a big deal and the sound really could go away completely... and I just need to get the miles on the rear end and do its service at 800-900 miles to change the rear end fluid after the breakin.

This noise is really annoying and loud enough that I can't squelch it with my stereo... in large part because of the pitch it's at.

Hoping for some good advice here. My wallet is scared.

 

[old-hot-rodder]

ZF Trans.

I just went through this. I would guess you do not have Genuine "Dana" gears in the rear end. Dana gears are 4:10's. Dana uses a grinding process which leaves the gear real smoothe. Other manufactures use a hobbling process that leaves ripples in the gear. This is what I would guess you hear. This is my story and I am sticking to it!
93 ZR-1 #407
Dana 4:10's and quiet!

 

[Skant]

It has Tom's Gears in it.

What doesn't make sense though is that this sound seems to be coming from the transmission, not the rear end. At first I assumed that the rear end is the new thing, so that must be where the problem is. But as far as I can tell, the rear end is quiet. It seems to be the tranny that's making the noise.

 

[old-hot-rodder]

ZF Trans.

Mine sounded like the trans also. The aluminum housing and and aluminum driveshaft echoed all the way up the tunnel. Maybe it IS the trans. but I changed my rear end 3 times last summer to get rid of the noise you describe. The Dana Viper gears that are only available at *Dodge, cured the problem 100% Thats my story and I sticking to it!
93 Torch Red #407
Plate (1BADZR1)