pinion shaft bearings

[Mektek]

While replacing the pinion shaft seal I noticed roughness when the shaft rotates. At 235k miles it's probably time for replacing the bearings.

I have a list of Rock Auto parts that I think covers the separate bearings and races. Can anyone confirm that I have the right combination for a 8 inch rear?

BCA NBM86610 Race Only Rear Outer; Trailblazer Base Model; with 7.25 IN or 8 IN Ring Gear

BCA NBM86649 Rear Outer; Trailblazer Base Model; with 7.25 IN or 8 IN Ring Gear;

BCA NBM802011 Race Rear Inner; Trailblazer Base Model; AAM; with 8 IN Ring Gear;

BCA NBM802048 Rear Inner; Trailblazer Base Model; with 8 IN or 8.625 IN Ring Gear;

 

[Mooseman]

Did you get a new crush sleeve? GM#9785792

More Information for DORMAN 81058

 

[JayArr]

It's hard to say until you tear into it but Rock Auto has a good return policy so I often 'over order' to have a variety/selection and then return the parts I didn't need when the job is done.

I prefer this to being short a part and waiting days for it to arrive.

 

[Mooseman]

You should try to find the OEM part numbers and cross reference them. Those description for 7.25 or 8" doesn't inspire a lot of confidence in me.

Those parts are fairly common. Should also be available locally or at a dealer. I'd also go with a better known brand like Timken.

 

[Mektek]

bca is division of NSK which is the oem of the GM ac clutch bearing. Should last the next 100k miles before the engine or transmission blows up
I'm going to recycle the crush sleeve - it can be hammered out to the original length. Its only function is to allow more torque on the pinion shaft nut.
I think it's stupid that the listings don't indicate what bearing matches a race.
I don't think I can mix a bca bearing with a timken race -- or can I????

 

[Mooseman]

I wouldn't.

 

[Mektek]

I think I'll go with these parts. Looking at the part numbers it seems not to be a coincidence that the inner and outer races end with 10 and 11 and the bearings end with 48 and 49.
I'll also be replacing the open diff with a g80 while all the parts are out. I'll be reusing as many of the old parts as possible.

 

[Mektek]

Got the bearings today. Expected made in China and was plesantly surprised to see made in Japan. They do seem to be well made and rotate smoothly. So I don't think there would be any advantage to spending more on timken etc.

 

[gmcman]

While replacing the pinion shaft seal I noticed roughness when the shaft rotates

When did you rotate the shaft to discover this...before you removed the seal and nut, when the seal was removed, or after you replaced the seal and nut?

When you replaced the seal, did you mark the shaft and nut......lol......... before you removed the nut? Did you replace the nut and tighten only a tiny bit past where the marks line up? I'm talking about the width of the mark.

Are you sure you have a bad pinion bearing, and not feeling the gears mesh or the spider gears turning?

If you have a bad pinion bearing, safe bet you could hear it under load.

Not saying you don't have one, sometimes, a leaky pinion seal can follow a worn bearing, but if it was quiet before, I want to speculate something else could be going on.

 

[gmcman]

I'm going to recycle the crush sleeve - it can be hammered out to the original length. Its only function is to allow more torque on the pinion shaft nut.

This is a real bad idea.

Sorry for the double post, but please don't do this. The crush sleeve is designed to be flat on both ends and takes ALOT of torque to crush down. Once used, it can be crushed further but trying to return to shape will only weaken it's amount of pressure exerted.

 

[Mektek]

After replacing the seal, I noticed there was still lateral play in the shaft. I tightened the nut past the index mark until the play was eliminated. Just rotating it back and forth within the limits of backlash I could feel roughness.

There certainly could be other problems. There was some noise only while decelerating 35 to 20mph.

I'm really not worried about recycling the crush sleeve. I'll add 2 or 3mm to the length of the sleeve - either by hammering it out or adding steel washers. Maybe I'll use some loctite on the nut as additional protection from loosening.

 

[gmcman]

After replacing the seal, I noticed there was still lateral play in the shaft. I tightened the nut past the index mark until the play was eliminated. Just rotating it back and forth within the limits of backlash I could feel roughness.

Perhaps you tightened the nut too far? It doesn't take much to overtighten. Especially bearings that are not new, the rotating torque is less when reinstalling the nut using old bearings.

If you tightened the nut one flat of the nut past where it was, then that is likely way too much. Generally you mark the nut and make a line on the nut and the end of the shaft. When reinstalling the nut, you would tighten about 1/16" past the mark, basically about one width of a sharpie mark.

A new crush sleeve is less than $10 from RA. I believe the inner race of the bearing is tougher than a washer. So when you apply about 200+ foot pounds to crush the sleeve, it might dig into the washer, deforming it.

I would really advise using a new crush sleeve, since you have to pull the carrier to replace the pinion bearings anyway, so you can get an accurate rotating torque reading.

You can't guess this procedure, you need a dial inch-pound torque wrench.