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ford 9" pinion bearing failure

6K views 23 replies 8 participants last post by  P&B PERFORMANCE P.BASSETT 
#1 ·
I am helping a friend with a new combo in a truck with a stick shift and this is what has happened to the inner pinion bearing twice.. It keeps trying to push the bearings out of the race and into the cage. Any ideas why this would happen?

 
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#4 ·
new crush sleeve preload set to specs turns smooth as silk when it is out. 50 weight synthetic fluid
Definitely wouldn't use a crush sleeve - get a solid spacer with shims.

I don't understand using the 50 weight fluid, I would go to a heavier fluid - at least a 70-90w.

How long did it take for the bearing to fail - street miles/runs down the track? How heavy is the truck and what short times does it do?
 
#5 ·
no street miles 6 1/8 mile passes... not sure on short times had tranny shifting issues and was on first good lanch when this happened. truck is prob 3000 or so.
 
#10 ·
who's bearings are you using.... ? i doubt its the crush sleeve.... UNDER power it wants to rip itself out and ride up the gear, so it is pushing against the race, unless the race can move back there is no way for it to change the pre load....
UNDER decel it would have the opportunity to pull in and that could change the pre load... i do not believe that's the problem
 
#12 ·
It has been hot, you can see the heat in the burned red coating, Looks like a low gear {small pinion dia} so there is much pinon speed. Need to use good made in America bearings, open the oil passages in the pinion support, don't use silicone when you instal the center section in the housing {some of the silicone breaks free and plugs or restricts the oil supply holes in the support. I have always broke the gears in with mineral 50 wt motor oil {on the jack stands-light dyno pull} then had good gear and bearing life with Mobile One synthetic 75-140 wt..
Need to check very closely the casting around the tail bearing, quite often they crack allowing the gear to run off center under load placing added stress on the pinion support bearings..
Helps to have the bearings R.E.M. treated..
 
#13 ·
It has been hot, you can see the heat in the burned red coating, Looks like a low gear {small pinion dia} so there is much pinon speed. Need to use good made in America bearings, open the oil passages in the pinion support, don't use silicone when you instal the center section in the housing {some of the silicone breaks free and plugs or restricts the oil supply holes in the support. I have always broke the gears in with mineral 50 wt motor oil {on the jack stands-light dyno pull} then had good gear and bearing life with Mobile One synthetic 75-140 wt..
Need to check very closely the casting around the tail bearing, quite often they crack allowing the gear to run off center under load placing added stress on the pinion support bearings..
Helps to have the bearings R.E.M. treated..
Agree pretty much with this except this:

The bearing may have gotten hot but I'm not sure we can come to the conclusion that the root cause is lack of lubrication just from that picture. When a bearing has a mechanical problem it will overheat even with proper lubrication.

I suspect there is something going on that is not related to lubrication and the overheating occured after the mechanical damage happened. In an earlier post he said they made 6 or so 1/8 mile passes. It would be unusual for a bearing to overheat under those conditions if there was any lubrication at all. And even if it did overheat first, I'm not sure that mechanical damage would occur so quickly with only 6 passes.
 
#14 ·
How much oil did you have in the rear? Reason I ask is I use to not fill mine all the way to the fill plug. Last year I only put about 2 or 2 1/2 quarts in with my new gear.
It starved the pinion bearing after just 2 passes. (Drag racers do get oil slung to the pinion bearings during burn out which helps, but I don't do burn out's of course)
When you launch the gear oil goes back, up and away from the pinion. It doesn't take long to run it dry if you don't have enough oil.

Just a thought.
 
#16 · (Edited)
Unless you pick the truck up and place it at the starting line ?

if not your pinion bearing has oil on it, and even then it has oil.

I had a customer drive a few miles on a DRY diff. . . .completely dry diff other than the redline oil i put on the race face with a brush during final assembly...
DRY, he gave it to his mechanics they put it in and then he or she drove that home over 2 miles, next day he calls and says the rear was fine for halfway home and then started making noise....

When i got it back the bearings didn't look exactly like these, the gears were totally worn out and melted looking and all kinds of shavings which got into the bearings and wrecked them.

That's dry, if the vehicle moves the ring gear is moving oil to the pin, and the pin is sitting in oil at rest, unless you only put 1/2 a qt in.

Something else is happening here, and i'd like to see pics of the front bearing and this entire diff totally disassembled.
 
#17 ·
yup

may be that the wrong race is installed for the bearing, and such that not all of the rollers are contacting their entire length into the race.

and or the wrong PAIRING of the RACE to the BEARING....

there is a "odd" thick and a thin bearing that has to use the proper corresponding RACE...

as said, or the race is not squarely installed

or the guy installed the race with a chisel and damaged the thin side of race so that the rollers do not have a smooth surface to contact and run on........

I had a guy that I sold three sets of bearings to..he damaged every one of them because he used a giant punch to install them into the pinion retainer housing.... left a giant flat spot...
he said that it did not matter because the rollers would "wear it in"...
but he wondered why it would only turn halfway and then lock up stop......(STUPID)
he also gouged the bearing seperator cage on one of the spool carrier bearings because the long punch that he was using hit thru the holes in the threadded aadjuster and nicked inside HARD...


whaddyaexpect.....????
 
#20 ·
but would someone actually make that mistake???

I had a customer that 3 times put some cheap cheap cutting stlye oil in his brand new set up diff, 3 times wrecked the thing and then blaming me. . . only after he sent the gears out to be checked did he believe me you can't use any oil you want

With the things i've seen anything is possible
 
#22 ·
also years ago,

had a guy that had a giant blow thru / crack in the rear cover of his 10 bolt / 12 bolt GM rearend..
due to him breaking the pinion and cross gears inside...pushed the broken crap all out the cover....

....so he hammered the blown thru cover closed and welded it up....
... and smoothed it all ....rounded inside the cover..

it would not squirt oil to the left carrier bearing..

I asked, " why did you spend two hours welding and grinding when you could have just taken another one out of five dollar junk yard and put it on..."
do ya know that the Vee groove is there for a reason...???

he said that he did not have a ride to get to the junkyard..but he had a hammer and welder..so he fixed it...


anything is possible....!!!!
 
#23 ·
and also have had numerious people replace the spanner nut lock tang BOLT with a longer one...

....and for some odd reason, ...
after it was all tightened up..
the carrier roller bearings had a flat spot / tight spot when he ran it..


bolt hole threads go thru to the bearing bore and will pinch the race...!!!!
 
#24 ·
Looks like mechanical problem. what case?pinion support?,gears? did pinion nut back off? case around rear pinion pilot bearing common to crack and flex. some people grind the case for clearence(very bad idea) if nodular support, was yoke cut back for full pinion nut enagagment? no chinese made bearings!!best to use solid spacer but not likley the problem here.
 
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