"Set-Up" pinion bearing for rearend build

[ProStreet78z28]

This seems like the way to go. Does anyone have anything to say about it? Or possibly already have one they used and no longer need it?

 

[Fbird]

Have never used 1. If your using an 8.5 10 bolt....use the .034 shim with your NEW pinion bearing! I've never had a difficulty. Pinion depth hasa always been within +/- .002 of nominal number!

Or if you have all the measuring equipment you can measure the original pinions depth. then measure the the pinion gear from face-bearing shoulder. do the math....wala....

 

[ProStreet78z28]

That would surely be close for a properly set-up rear, but some douch bag set up my current rear up wrong and I need to start from scratch.

 

[BondoSpecial]

I wouldn't use one....I have never had a set up bearing give the exact depth. At best I have had them be off by .001-.002 and the 8.5 I just did, the set up bearing was off by a full .003 or .004. If you trust a set up bearing and press the real bearing on and find out the pattern has moved, and you don't have a plan B for removing the tightly pressed-on pinion bearing without damaging it, you are in trouble. I recently wound up buying a very over priced Yukon clam shell pinion bearing puller so I can remove pinion bearings over and over again now without damaging them so I don't need to rely on a set up bearing.

If your using an 8.5 10 bolt....use the .034 shim

No. The 8.5 I just did had a .039 factory shim and with new GM gears it set up at .043. Guessing on shims is asking for problems, and the nominal shim in an 8.5 is around .040" anyway. If you are shooting for a perfect pattern, every .001" shim change counts. If you are going to do this job you might as well try to do it correctly because taking a rear apart is not something you want to do multiple times.

 

[ProStreet78z28]

I want a set-up bearing to get me in the ball park first. It doesnt make sense to me to pull a bearing off 5 or 6 times to see where I sit and risk damaging the bearing. A set-up bearing will get me close, the final bearing will get me there (maybe pull it back off only once). Of course many people including the pros have used set-up bearings with no ill effects. I have plans to adjust and check with the real bearing anyways.

 

[BondoSpecial]

Have you ever set a rear up before? I don't even know why you are asking for advice. A checker bearing is better than nothing but it sometimes winds up being so far off that you get a false sense of being close, then press your real bearing on, find out you are way off, and have to start over again.

 

[ProStreet78z28]

Have you ever set a rear up before? I don't even know why you are asking for advice. A checker bearing is better than nothing but it sometimes winds up being so far off that you get a false sense of being close, then press your real bearing on, find out you are way off, and have to start over again.

I understand that is a possibilty. I just want first hand knowledge on how likely that is. I would imagine timken bearings would have very good quality control for accuracy of bearing to bearing variables. I'm only doing this once, which doesnt justify the purchase of a press or a tool. Unless absoluty a must.

 

[BondoSpecial]

Ok I will break it down this way. I have done 3 Ford 8.8 setups, two GM 7.5 setups, and three GM 8.5 setups. The checker bearing was NEVER correct to 0.000" accuracy. Like I said, at best only .001 or .002 off, at worst .003 or .004 off. Even being off by only a few thousandths is a problem because you need to get pinion depth correct within .001" if you really want the rear to run as quietly as possible.

This is not a job you can do without at least a $99 harbor freight shop press and a $25 bearing separator. It would be like trying to remove wheels on a car only having a pair of pliers. It's just not gonna end well. The $25 bearing splitters get pinion bearings off maybe 75% of the time without damaging them. I would buy a few extra Timken pinion cones (M88048, they aren't expensive) and buy a $25 ebay bearing splitter to use with a shop press, in the case you damage one getting it off.

 

[BondoSpecial]

Here are some pictures showing exactly what happened when I went from a Timken M88048 bearing honed out to another Timken M88048 bearing setting up my recent 8.5 rear:

.046" pinion shim with honed out Timken pinion bearing:

.046" pinion shim with new Timken pinion bearing-look how far too deep the pattern is just changing from the checker bearing to the real bearing. If you couldn't press this off you'd be screwed, and you'd have a noisy rear

.043 shim after removing new bearing and pressing it back on to change shims

 

[ProStreet78z28]

Ok I will break it down this way. I have done 3 Ford 8.8 setups, two GM 7.5 setups, and three GM 8.5 setups. The checker bearing was NEVER correct to 0.000" accuracy. Like I said, at best only .001 or .002 off, at worst .003 or .004 off. Even being off by only a few thousandths is a problem because you need to get pinion depth correct within .001" if you really want the rear to run as quietly as possible.

This is not a job you can do without at least a $99 harbor freight shop press and a $25 bearing separator. It would be like trying to remove wheels on a car only having a pair of pliers. It's just not gonna end well. The $25 bearing splitters get pinion bearings off maybe 75% of the time without damaging them. I would buy a few extra Timken pinion cones (M88048, they aren't expensive) and buy a $25 ebay bearing splitter to use with a shop press, in the case you damage one getting it off.

Can I just borrow your puller lol...