Front pinion bearing question

[DWinTX]

I just finished rebuilding (and upgrading) the engine and transmission on my 65 Coronet, and the last thing I need to do is the rear end. I'm switching from an open 2.94 to a 3.55 Sure Grip. I'm putting it together now and at the point I need to set the pinion depth.

I used the trick to get two rear pinion bearings and hone one out to make it easier to test different shim thicknesses. But ran into a problem when trying to assemble the pinion. The front bearing will not slide over the pinion shaft. Seems like the ID of the bearing is a thou or so smaller than the shaft.

This is the first rear end I've set up so I don't know if this is normal or not. Can I just hone a bit off the ID of the bearing? It is a brand new Motive Gear set from Dr. Diff.

 

[Fran Blacker]

If you set the depth with the honed bearing and depth is set? Your trying to install the bearing for final assembly it's a press fit. Another way to put the bearing on is put pinion in the freezer for 30 mins or so. Warm inner bearing in a 200 degree oven or with propane torch, don't over heat it. With shims in place it will drop right on. When it gets to room temp your done.

 

[DWinTX]

OK, I didn't realize that the front bearing was a press fit too, I thought it was just the rear. The old front one just fell right off when I pulled the yoke out. I'll hone this front one for setting the depth and get another for final assembly.

 

[Fran Blacker]

OK, I didn't realize that the front bearing was a press fit too, I thought it was just the rear. The old front one just fell right off when I pulled the yoke out. I'll hone this front one for setting the depth and get another for final assembly.

Your right my screw up. Yes it should slip on.

 

[Yatzee]

I just finished rebuilding (and upgrading) the engine and transmission on my 65 Coronet, and the last thing I need to do is the rear end. I'm switching from an open 2.94 to a 3.55 Sure Grip. I'm putting it together now and at the point I need to set the pinion depth.

I used the trick to get two rear pinion bearings and hone one out to make it easier to test different shim thicknesses. But ran into a problem when trying to assemble the pinion. The front bearing will not slide over the pinion shaft. Seems like the ID of the bearing is a thou or so smaller than the shaft.

This is the first rear end I've set up so I don't know if this is normal or not. Can I just hone a bit off the ID of the bearing? It is a brand new Motive Gear set from Dr. Diff.

It can be a bit difficult, if not impossible, to hone the inner section of a bearing and maintain accurate roundness. Cleanliness is the word here and hanging onto the inner race could be a bear. Furthermore, bearings are made of some pretty hard material. A better way is to try and reduce the shaft where the bearing sits but again the pinion shaft is heat treated and hardened as well. You could try a flap wheel on the bearing's ID and then the temperature application. You've obviously bought some sub-standard parts and should return them for something that's more highly engineered as longevity relies on proper sizing. What brand of bearing is it because they're usually pretty accurate - I'd tend to think that the pinion shaft is the problem.

 

[Fran Blacker]

I go to the local parts store with the pinion and try another bearing. If that one doesn't fit time to call who sold the gears to you or the manufacturer.
That is if you'll even read this after that first screw up!

 

[DWinTX]

I honed the bearing so I could do the pinion setup, but I ordered a couple spares from RockAuto. I had to get the final rear bearing anyway and the fronts are only 7 bucks apiece. Unfortunately, none of the stores around me carry them. They are Timken bearings, so not cheapos. The gears are Motive Gears.

I'm going to email Dr Diff tomorrow. I guess I can measure the shaft and he can tell me if it's off.

 

[Fran Blacker]

Do you have the gears that came out to compare with one your installing.

 

[DWinTX]

Yes, I tried and the bearing wouldn't fit over the old pinion either. Those bearings have the same part number, so maybe the problem is the bearing. We'll see what the others look like.

 

[miller]

Be sure you're getting the right bearing number.

 

[DWinTX]

Yep, both the old and new bearings are M88048.

 

[Fran Blacker]

Yep, both the old and new bearings are M88048.

Did you try the old bearing you removed from original gears on new gears? If old bearing fits, take the number off that if a different brand and to cross reference it.

 

[DWinTX]

Yes, the old bearing didn't fit the new pinion shaft either. I did measure the shaft but can't remember what it was. I'll do that again when I get a chance. Timken's site shows the bore on the M88048 as being 1.3125. The shaft should have a diameter of that or less I would assume. I'm thinking the shaft is off.

 

[miller]

Do you still have the old pinion shaft, to compare the diameter, old vs new? The bearing races are case-hardened, real tough, not something you would want to try to hone.
If the new pinion shaft diameter is too big, I'd think it would be better to take it down, until the bearing fits. At least, that's what I'd do. Might not be that much difference.