View Full Version : Setting Pinion Bearing Preload ?

05-19-2005, 10:54 AM
Does anyone have any helpful hints,suggestions,or methods for setting pinion bearing preload on a 12-bolt Chevy rearend ? I've rebuilt several of these rearends,but I've always felt uneasy or unshure of the pinion preload. I've got an inch pound torque wrench to check the setting,but my question is how to get to that point. Right now I'm having to replace the pinion bearings,crush sleeve,and pinion seal in my 1969 Camaro because I had the preload to tight and the bearings are now noisy.

05-19-2005, 11:27 AM
My #1 suggestion to you is to use a SOLID pinion spacer and forget the crush sleeve. Just like you I had to R&R the pinion bearings, crush sleeve and such on my 12-bolt (more than once) because I got the pinion preload too tight.

Using a solid pinion spacer doesn't require anywhere near the measure of torque to get pinion pre-load correct since there's no "crushing" involved. With a solid spacer, tightening the pinion nut increases the pressure applied between the bearings and the races until the bearings come to a positive stop against the spacer. By allowing the spacer length to adjust via added shims, the effective length of the spacer can be set to stop the bearings where they are preloaded correctly against the inner bearing races. This is the bearing preload. By placing an inch-pound torque wrench on the pinion nut--after it is tightened to the proper torque spec--and turning the nut, the torque wrench measures the resistance the bearing is subjected to. If the preload (inch-pound number) is too high, adding the appropriate shim will back them away from the races, lessening preload. If the pinion is too loose, removing some shim will allow them to bear more tightly into the races, increasing preload. To determine the required shim thickness, the yoke and spacer may need to be removed and installed a few times until it's correct, but the procedure is pretty simple.

Best of all, it's reuseable! Some people don't like solid spacers for street applications because they state they allow the pinion nut to loosen up over time. That's true ONLY if they don't use Loctite (blue) and/or torque the pinion nut to the required specification. I'll NEVER go back to a crush sleeve and have had my solid spacer installed for many thousands of miles w/o problem.

Solid pinion spacers for 12-bolts can be purchased from Jeg's/Summit.


05-19-2005, 12:47 PM
Wow ! The solid spacer actually seems to make more sense than a crush sleeve.
I did not know such a thing existed. I'll Give it at try.Thanks Dan !

05-19-2005, 07:51 PM
Ratech also makes kits.