Knuckle Bearing Preload Problem (1 Viewer)

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Joined
Dec 5, 2009
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4
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Location
Albuquerque, New Mexico
I am wrapping up a disc brake conversion for a 75 FJ40. When the knuckle is shimmed to a 10 pound pull using a fish scale I can feel prominent bumping in the bearings as I rotate the knuckle. After adding a .010 shim the pull goes down to 3 pounds and a very slight bumping in the bearing as I rotate. I did visually verify the new bearing races were seated and took measurements at each quadrant and they appear to be parallel best I can measure (calipers). Is this bumping feel when rotating these knuckles acceptable?

Anyone have any suggestions?
 
My bearings felt like that before I replaced them.

Are the bearings new? During set up did you tighten them without enough shim an crush the rollers into the races?
 
Did you grease the bearings? (not trying to be a wise guy)
 
The bearings and seats are new and I greased them before installing. The first pull measurement gave me 10 pounds then I backed off and added a shim for a 3 pound pull. I have only done one side so far since I am concerned with the bearing bumping issues.
 
Are you sure that these are the proper Koyo replacement bearings for your rig and/or that the races are fully seated?
 
I ordered the kit for a 79 FJ40 and the axle housing including the knuckle balls are from a 75 FJ40. Although I am pretty sure they are the same size knuckle balls so i don't think this is an issue. The bearings are Koyo TR0305AF4 which came with the SBKL kit from JT Outfitters.

Do these bearings seem like the correct part number?
 
Can you get you hands on the SST to measure where and how much to shim your knuckle. Who knows what has been done in the past by others. It is the only way to be sure you are getting it right.
 
Although the knuckle centering is important, these symptoms don't sound centering related and you can set the preload without the SST. Were the bearings sealed in their original packaging when you received them? Does the bumping relate to the distance between the rollers? I would do the other side and see what happens.
 
The bearings were sealed in original packaging and I have been meticulous about keeping the associated bearings and races together. Yes, the bumping appears to be the distance between the rollers. With regards to the centering, both the donor and original axle had a .040 shim (both sides) on the lower cap. Based on the original shim configuration I figure the centering should not be a concern plus I am installing the Marlin Crawler EcoSeal inner axle seals as a precautionary measure.
 
BTW, I have checked the pull weight measurement with three different scales. I did not trust the 10 pound measurement since it felt rather tight when rotating. To the point that it was much tighter than all four of the knuckles prior to tear down. For what it's worth I do NOT have the wiper seals installed.
 
Could be as simple as a bad bearing. Possibly a distorted race.
+1 on trying the other side and see what's up
 
I will go ahead and install the other side tonight and see how that goes. Any suggestions on how to determine if it's a lower or upper bearing causing the bumping?
 
I ordered the kit for a 79 FJ40 and the axle housing including the knuckle balls are from a 75 FJ40. Although I am pretty sure they are the same size knuckle balls so i don't think this is an issue. The bearings are Koyo TR0305AF4 which came with the SBKL kit from JT Outfitters.

Do these bearings seem like the correct part number?

Yes, they seem to be the correct numbers. From my notes collection:

Knuckle:
Set of Bearing & Race: KOYO TR0305AF4 [replaces TR0305A] [Set KOYO 30303D steeper, not in usa] For reference, the actual KOYO part number is TRO305AF4 (on the box) and TR305A on the bearing and the race.

Did you assure that the races were fully seated?
 
I am pretty sure the races are fully seated but it's hard to tell and measurements are somewhat crude. I will start will the other side tonight and see how it goes. If it works okay I am thinking I will start over with the problem side. I will repack the bearings and check it again. If no success, I will pop the races out and swap the upper bearing set with the lower set.

Any other ideas I should consider trying?
 
Last week I was doing knuckle rebuild , went to put in new bearings & races, and low and beholed , old races were stamped 2.2 camber , p.o. must have done this, may be worth checking yours, & may have nothing to do with your problem, my 2 cents, John
 
I am pretty sure the races are fully seated but it's hard to tell and measurements are somewhat crude. I will start will the other side tonight and see how it goes. If it works okay I am thinking I will start over with the problem side. I will repack the bearings and check it again. If no success, I will pop the races out and swap the upper bearing set with the lower set.

Any other ideas I should consider trying?

You can get a visual by looking through the inside out. When looking down at the lower race, there will be two indents/half holes where you place a punch for removing the races. There should be absolutely no gaps between the bottom of the race and the knuckle. When installing, I use an aluminum race installer, but a brass drift/hammer works almost as well. Plus, there's a change in the sound as you pound the race in and it hits bottom.

I've only heard of this situation you describe with a worn race. As was mentioned, you may have defective bearing/race.
 
Problem solved!

The passenger side went smooth with a little extra time on packing the new bearings. I then went back to the drivers side and repacked the bearings and reassembled. I was pleasantly surprised when the problem was solved with simply repacking the bearings. Bottom-line, make sure the bearings are completely packed to avoid problems.

"Life is good"
 
Cool! Always nice when the simple solution works out. Must sacrifices to the garages gods now.
 
So, What should the pre load be? In the range of what to what?
 

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