Major rear-end clunking after gear change

Stokestack · 02-02-2006, 09:36 PM

Hi all.

I recently had 3.73s put into my '96 Cobra, and now there's a boatload of noise coming from the rear end. Not only does it clunk on shifts, but often when going around turns it sounds like I have a trunk full of golf balls. Seriously.

It sounds like something is shifting significantly when the drivetrain is engaged or disengaged.

Some people have suggested that the installer forgot to add friction modifier. Is that likely to account for such a panoply of noises? And what's the procedure for adding modifier (including removing some gear oil to make room, and where is the filling location)?

Thanks!

Gavin

Jeff Chambers · 02-03-2006, 07:40 AM

Poor setup most likely. Friction modifier wouldn't cause what you're describing. There are a number of things that it could be; inadequate pinion bearing preload, inadequate carrier bearing preload, too much backlash, or pinion depth not correct. I'd have a qualified shop take it back apart for inspection and proper assembly.

bigwhitecobra · 02-03-2006, 10:01 AM

Wow you got screwed.

I would say that they didn't crush the crush sleeve and the pinion is dancing around like a little ballet dancer. Just a guess though. I would yank it out immediately if not sooner and get that thing fixed, before you are out a gear. That sucks to hear. Hope it works out for you.

Stokestack · 02-03-2006, 05:19 PM

Thanks for the responses, guys.

Man, you can do research, ask around, and try to verify the quality of shops, and you still wind up with crappy work. To top it off, I had a bunch of suspension upgrades that wound up lowering the car too much.

But that's a topic for another thread, which I'll start now...

Gavin

02-02-2006, 09:36 PM	#1
Stokestack Registered Member Join Date: Feb 2006 Location: Los Angeles Posts: 4	Major rear-end clunking after gear change Hi all. I recently had 3.73s put into my '96 Cobra, and now there's a boatload of noise coming from the rear end. Not only does it clunk on shifts, but often when going around turns it sounds like I have a trunk full of golf balls. Seriously. It sounds like something is shifting significantly when the drivetrain is engaged or disengaged. Some people have suggested that the installer forgot to add friction modifier. Is that likely to account for such a panoply of noises? And what's the procedure for adding modifier (including removing some gear oil to make room, and where is the filling location)? Thanks! Gavin

02-03-2006, 07:40 AM	#2
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: Major rear-end clunking after gear change Poor setup most likely. Friction modifier wouldn't cause what you're describing. There are a number of things that it could be; inadequate pinion bearing preload, inadequate carrier bearing preload, too much backlash, or pinion depth not correct. I'd have a qualified shop take it back apart for inspection and proper assembly. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

02-03-2006, 10:01 AM	#3
bigwhitecobra Huh? Whatcha said? Join Date: Oct 2000 Location: Fayetteville, NC Posts: 1,073	Re: Major rear-end clunking after gear change Wow you got screwed. I would say that they didn't crush the crush sleeve and the pinion is dancing around like a little ballet dancer. Just a guess though. I would yank it out immediately if not sooner and get that thing fixed, before you are out a gear. That sucks to hear. Hope it works out for you. __________________ 2003 GT White---STOLEN May you burn in hell whoever took it. Dumbazz didn't even get the good engine that was in the garage.

02-03-2006, 05:19 PM	#4
Stokestack Registered Member Join Date: Feb 2006 Location: Los Angeles Posts: 4	Ho hum Thanks for the responses, guys. Man, you can do research, ask around, and try to verify the quality of shops, and you still wind up with crappy work. To top it off, I had a bunch of suspension upgrades that wound up lowering the car too much. But that's a topic for another thread, which I'll start now... Gavin

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