Pinion shim does not sit flat

[Bailey28]

Got into my '84 10 bolt. I have a new GM ring a pinion gear on the bench ready to install. I made a slip fit inner pinion bearing so I can get the bearing back off when fitting different thickness shims.

My question is why don't the new shims sit flat against the backside of the pinion gear when I drop them on? Even with the bearing resting on the shim it won't sit flat. The pinion gear has a radiused shoulder where the shims sit keeping them from sitting flat...

I took one of the shims and enlarged the inner diameter to get it to sit flat around the shoulder and that allowed the bearing to flatten the shim out against the pinion gear. However I cannot get the shim to stay centered. The shim will most likey hang off center and get pinched between the bearing flange and the shoulder when installing it....

Am I overthinking this or should under no circumstances there be a .030" gap between the shim and the gear? I am doing gears for the first time. It seemed so elementary to just 'put the shims on'....now this...

 

[Bailey28]

Pic of gap. See the shoulder?

 

[Bailey28]

The folks who made these gears

 

[Bailey28]

Shims fit well around the pinion shaft but dont sit flat..

 

[pontiacgp]

I don't think you have the correct shims...

 

[Scoot-71]

I do a lot of rear end work on Fords but dabbled with chevys too, I am surprised that there is a radius that big in that pinion, however either you find different shims or enlarge the shims you got, the shim don't need to perfectly centered but do need to sit flat off that radius. what is the diameter of the needed to clear radius??

 

[Scoot-71]

I do a lot of rear end work on Fords but dabbled with chevys too, I am surprised that there is a radius that big in that pinion, however either you find different shims or enlarge the shims you got, the shim don't need to perfectly centered but do need to sit flat off that radius. what is the diameter of the needed to clear radius??

For reference a 8.8 ford pinion shim inner diameter is 1.750

 

[pontiacgp]

without the shims does the bearing sit properly on the pinion?

 

[Bailey28]

I don't have a way of getting the old shim off. As best I can measure the stock shim is .030" thick. I have several new shims which measure 1.455" ID.

The pinion shaft is 1.440" right at the point the shoulder starts.

I enlarged one of the new shims to 1.560" where it sits flat away from the shoulder.

PontiacGP, the shim in your pic looks narrower than the shims I have however my new shims fit absolutely perfect around the pinion shaft. Without the shims the bearing fits perfectly flat. No daylight what so ever.

It seems the shoulder is killing me. I've been looking at pics of pinion gears online and it seems that most of them are machined to 90* right at this area and don't have a pronounced shoulder. If I had the pinion gear put on a lathe and the shoulder taken down would it compromise the gear?

 

[Bailey28]

The kit I ordered came with KOYO USA bearings and was spec'd for a 82-up 7.5 7.625 rear.