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Pinion Bearing Failure

D

Dmondeac

NAXJA Forum User
Location
Midlothian, VA
I have 1500 miles on a new set of gears and bearings and now the pinion bearing has failed. I have not torn the front end down yet but I am betting that the Tru Trac is toast as well. Any ideas as to why the bearings would go that quickly. Also what diff would you replace it with?
 
Non Timken bearings and I set it up. Probably the bearings.
 
The TT may be marked up by the pinion but should still be useable.

I'm guessing too little pre-load and the bearings/races beat themselves up. Do you remember what your inch lbs torque wrench was reading on your final pre-load test? Did you read it without the ring gear installed or with? If with the ring gear, i guarantee you had too little of pre-load. I made this mistake years ago when first learning gear installs. I got excited and got ahead of myself.
 
I will check my notes, but i believe i had 20 in/lbs on the pinion pre load with oyt the ring installed.
 
Sometimes the bearing cups do not get fully seated and you get good readings when setting it up but when you drive it the bearing cups fully seat making the preload too low and causing the bearings to fail. How's that for a run-on sentence?
 
jeeperjohn said:
Sometimes the bearing cups do not get fully seated and you get good readings when setting it up but when you drive it the bearing cups fully seat making the preload too low and causing the bearings to fail. How's that for a run-on sentence?
Click to expand...

This.

Or they burned up from oil starvation...or they were contaminated (badly) with debris from the diff
 
There are 2 differences on the front diff than the rear, one is the oil slinger which is that big flat washer that sticks out way past the pinion gear. The other is the baffle that goes in the stack behind the front pinion bearing. Both of those help keep oil up around the bearings. If you leave them out, expect premature failure. The rear diffs don't use them as the ring gear is like a pump and throws oil down a passage way right at the front bearing.
 
markw said:
There are 2 differences on the front diff than the rear, one is the oil slinger which is that big flat washer that sticks out way past the pinion gear. The other is the baffle that goes in the stack behind the front pinion bearing. Both of those help keep oil up around the bearings. If you leave them out, expect premature failure. The rear diffs don't use them as the ring gear is like a pump and throws oil down a passage way right at the front bearing.
Click to expand...

I had my rear pinion bearing fail due to inadequate oil lubrication. The pinion is set at an angle high enough to prevent proper oil throw apparently. I have since then replaced it and overfilled the diff. Any other way to fix this potential future problem from reoccuring?
 
2001XJ said:
I had my rear pinion bearing fail due to inadequate oil lubrication. The pinion is set at an angle high enough to prevent proper oil throw apparently. I have since then replaced it and overfilled the diff. Any other way to fix this potential future problem from reoccuring?
Click to expand...
Put a large washer under the head of the pinion to slow down the oil flow back into the bottom of the diff. I am assuming this is an 8.25?
 
How much lift have you got? I'm running about 6" and 4 degree shims on my 44, it's been fine for 5 years. More lift means rotating the housing further to get the driveline lined up right.

Mark
 
jeeperjohn said:
Put a large washer under the head of the pinion to slow down the oil flow back into the bottom of the diff. I am assuming this is an 8.25?
Click to expand...

thanks, will remember this if it fails again and yes, its a C8.25 :wow:
 
Last edited:
markw said:
How much lift have you got? I'm running about 6" and 4 degree shims on my 44, it's been fine for 5 years. More lift means rotating the housing further to get the driveline lined up right.

Mark
Click to expand...

Yeah, I'm running somewhere between 6 and 7" (closer to 7). I can't remember what my rotation is set to. I used TNT 1.5" u-bolt eliminators so I don't have shims, the housing was rotated as needed then perches were welded on.
 
Isn't there usually a baffle that doubles as a shim underneath the inner pinion bearing race?

Looks like this:

16512.53-100x100.jpg


And goes here:

Pinion-1.jpg


I know I've seen it on just about every Dana axle I've worked on...
 
The rears may or may not have that. Fronts always, along with the slinger/.030 washer that goes between the pinion gear and the front pinion bearing. If it's eating pinion bearings, and is rotated pretty high, he should maybe decrease the lift with smaller tires/trimming, and/or consider putting a baffle in if it's available for that axle. Sounds like it will be some work to un-rotate the housing.
 
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