My 70 Charger has a cut down C body 8.75 '489 case with 4.10 gears and a Dana powr Lock clutch type diff. The Moser axles had extra long splined area, and were cut down to fit the housing, which is 2" narrower than stock 68-70 B body width. No problems with this setup, but it had me wondering...
I read somewhere that the diff center pin thrust button should be removed when using non adjustable axle bearings? True? My diff has the thrust button and I have had no problems with this 3rd member in 8 years of classic car use. Maybe I got lucky. I am ready to begin another project and would like to know any pitfalls, since the car will be restored and sold online. I dont want the next owner to have a failure if he decides to have fun with the car.

If the axles fit and don't but together with it in it won't hurt anything. It is just that with green bearings it is not nessessary because there is no preload/endplay to adjust.

if your cutting axle,then maybe it could be a problem IMHO

if its not measure correct,you could wind up with side load on the bearing..which they dont like

now,I did run a 489 case 3.55 cone sg with thrust block in for 9 yrs on the street

swaped to a 742 open and I cold chiseld the thrust block out and ran it for a few yrs

I did have 1 bearing go out in the 12 yrs I had them

on the 2nd set with the 742 and no thrust block

IMHO,if it has buttens and you can remove them..I would..it will remove any doubt on the axle cut measurments

I am running the a-body moser axles and asked them about the 489 block,said the axle is set to go with the block in or out

but you have cut yours down some correct??

this would be a good time to PM DrDiff and ask about the thrust block measurements and axle end spaceing..

I think what made my bearing fail was me hauling a empty car dolly 300 miles with it waging back and forth unloaded...that was a annoying ride empty as it wiggled the truck a good amount

couple days later I am on the new greens

I think the side loading back and forth got to the high milage green bearings

good luck