This 8 3/4' axle conversion is fighting me all the way. I test fit my Dr. Diff green bearing axles into my A body housing with a 741 case open differential (no SureGrip). The spiral ring around the bearing sits about 1/8" out when the other side is pushed all the way in. Clearly the thrust block in the center section is the problem, but I don't see how to remove it. It has a large slot through it that the pinion gear shaft goes through. Can the thrust block be removed, or do I need to have the axles cut slightly shorter? Thanks.

With the one-piece thrust block, the differential must be disassembled to remove it. I'd just shorten the axles.

Do certain cases have the one-piece thrust block?

My 489 case had a block that was two pieces. The 3rd member needs to come out and you need to look very closely at the pin holding the two halves together. One you can hammer on all day and not make any progress, the other will come right out.

When in doubt . . . check youtube ??? Or better yet, check back with Cass (Dr. Diff) . . . he da man !

Yep... Dr.Diff is da man.

Had a similar problem with my tapered axle diff (742 case with clutch type sure grip) after replacing the wheel bearings. The new ones were slightly narrower than the originals. Called Dr.Diff to see where to purchase the required shims and found that no one makes them anymore. Long story short, two alternatives... make your own shims or remove material from the thrust block. I did the latter. Had to remove .140 from the thrust block to get proper axle end play. He da man!

The OP has no Sure-Grip, the open differential and the cone-type SG have a one-piece block. Only the clutch-type SG has the two-piece thrust buttons.

Generally I leave the thrust button(s) in, and either fabricate flange spacers for the axle tube flange as I generally incorporate a rear wheel disc set up (.100-.110 thick each side) or cut the axle ends, there's plenty of spline for this

Thanks for the info, didn't know that.

Update: John's pic is exactly what I have. I woke up this morning realizing the brake backing plates might act like shims if the center hole diameter was small enough. I quick test assembly showed this was the case: the spiral ring on the green bearing butts up against the outside of the backing plate, not the housing flange like I first thought. The combined thicknesses of the two brake backing plates spaces the axles out just enough to avoid jamming into the thrust block. I have renewed respect for Dr. Diff's expertise! I am posting this to help others who might have this situation.

I have yet to see a thrust block that was in 2 pieces ... that wasn't broken somehow ... , what was the center section from ?