Gear Noise Upon Deceleration Need Help

[Deleted member 87397]

Gear Noise Upon Deceleration Need Help (Updated)

O.K. all you gurus I need suggestions. I've completely re-done my rear axle and suspension and it has taken me FOREVER to get it all back in the car due to lack of time. when i say forever I mean I had the rear end rebuilt like two years ago and just finally got everything put back together. I finally got all the last minute stuff done today and took it for a test run. At very low speed like below 10 and also on deceleration it's making a noise in the rear like the gears are not meshing properly. If I accelerate normally or fast and stay in the gas it does not make the noise. The second I let off the gas and the drive line tension is released, it starts this noise. I'm wondering if maybe there's too much drive line slack, bad pinion angle, or if something wasn't done right when I had the rear end rebuilt. Though I watched while the gears and diff were being installed and everything looked great. When the guy applied the gear marking compound and spun it, everything matched up nicely. I've changed out literally everything in the rear end and suspension so the problem could be anything. Here's specs on everything I've done.

8.8 housing with axle tubes welded
31 spline Auburn Posi
Ford Racing 3.73's
Moser 31 spline 5 lug axles
Moser Diff cover with girdle
Pinion flange on the diff is a newer larger diameter one like on 03 cobras and larger trucks since I ditched the old rusty one thinking I could pick up a new one. I put a new matching flange on the FRPP drive shaft with a new u-joint to match. I installed the driveshaft 5 or 6 months ago and can't remember how much play there was in the new setup. I will have to check on it.

Transmission is a TKO 600

Suspension:

Stock new UCA's
Maximum Motorsports HD adjustable LCA's
Adjustable Pinion snubber
QA1 Adjustable shocks
Ford Racing B springs

Sorry for the novel. Hopefully all you knowledgeable driveline guys can give me some suggestions. THANKS

 

[Kdubslugga]

To much backlash.. What was it set at do you know? I had mine done professionally and it howled like crazy, after paying 450 for the install, I vowed to never pay anyone to work on my car again. I dropped the carrier, reset the backlash to within spec, (0.08-0.015) and just like that, no more howling on decel!

 

[Kdubslugga]

And btw, I just learned in Physics class, that there is no such thing as Deceleration, which I think is BS, freakin professor said that even when your slowing down (example: slamming on brakes) thats called acceleration too!!! Just a little fyi for ya, I think its BS and will still call it Deceleration lol

 

[Deleted member 87397]

The noise isnt really a whining noise though. It's hard to describe. It kinda sounds like a freestyle bike when you stop pedaling and it makes that rapid clicking noise. I did some digging online late last night and apparently posi rearends are known for chattering, but this is pretty noticeable. Who knows, maybe it's normal?

 

[865.0HO]

I just went through the same thing on my 8.8 rebuild a couple months ago. Backlash was set at .012. I tore the rear end down, reduced pinion depth by .018 and added more shims to the carrier bearings to increase preload. Rear end is whisper quiet now.

 

[Deleted member 87397]

Man I don't want to tear this thing down. I realized earlier I may not have quite enough fluid in it. The pum I was using wouldn't reach the bottom of the jug I had so there's only about 1 and 3/4 in there. I've seen that diffs with the cap support covers like I have can hold about 3 qts. It would be awesome if it were that simple but I don't think it is.

 

[Deleted member 87397]

Took the diff cover off today and noticed the guy I had build it put the main caps on backward. So basically the carrier bearings aren't getting the oil they need and my fluid had a nice silvery sheen to it. Not sure if this will fix my noise issue, but it's highly possible. I'm going to put them on the correct way tomorrow and fill her back up. The guy that built it is supposed to be one of the best when it comes to gears and rear end setups. He must have been hungover the morning I went to see him.

 

[twistedwankel]

I just went through the same thing on my 8.8 rebuild a couple months ago. Backlash was set at .012. I tore the rear end down, reduced pinion depth by .018 and added more shims to the carrier bearings to increase preload. Rear end is whisper quiet now.

+1 on the shims.

 

[Kdubslugga]

+1 on the shims.

+2 on that. Side carrier bearing preload is a mistake i used to make. Make sure you have plenty of shims in that carrier

 

[Deleted member 87397]

Well since I have to pull the caps to put them on correctly I might as well check the carrier preload. Here's a pic of the compound markings.

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