Smoked another rear bearing. WTF?!?!?!

beerdog

Registered
How y'all doing? Thought I would bring this problem ear before I venture out into Facebook hell. A few years ago I smoked the drivers side knuckle bearing. this was about 30,000 miles since I rebuilt the rear suspension. I pressed the bearing in myself and am very confident I did it correctly. It has been about 10,000 miles and I blew the bearing again. This time I used the actual Ford bearing tools (thanks to Mark Darrah. He spends a lot of time on Ebay.) Replacing the bearing will not be a challenge, but does anyone have any idea why it would happen again so quickly? Maybe a damaged or bad knuckle?

When I rebuilt the rear suspension I replaced and rebuilt everything. Either new or very good used parts were used. Completly rebuilt the diff. Low mile half shafts. Poly knuckle bushings. When the bearing was good there were no odd noises or signs of problems. Then the oother day I heard a not soo happy noise and was like..."fuck. that does not sound good.".
 

beerdog

Registered
I need to add an edit. The first time I pressed in the bearing I did not use the Ford tool. I just rigged up some parts I had to ensure I pressed in the bearing on the outer race. The second bearing was pressed in using the Ford installation tools. The diff has a mustang non IRS trac-lok carrier. Hopefully that is not causing a problem.
 

driller

El Presidente
Staff member
My thought is it almost has to be a half-shaft issue causing end thrust on the bearing. As the suspension travels up/down, the half-shaft length changes slightly which should be accommodated by the inner CV joint. It the half shaft is not the proper length or if it binds laterally, it could be putting end thrust on the bearing.
 

billcu

Head Moderator
Staff member
I never did one of these but I'd check the boot and seal when you take them apart also. A bad seal wrecks the front bearings pretty quickly.
 

driller

El Presidente
Staff member
Can the CV joint be inspected on the car?
Sorry, I can't really say. Most that I've seen go bad were obviously bad without question.

Mostly on the MN12 variety, they twist off at the hub end under power hits at the launch on the track. 🤭
 
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