I have been getting conflicting information from different transmission shops. I have a 68 chevelle 8.2 10bolt. I spoke with the original owner and this was a 3.08 open rear and he put a eaton posi and 4.11 richmond gears in it. I want to change to 3.55 gears. Will I need to change this posi unit? I am looking in Jegs and it says 3.08 up for this type of unit. If the guy I bought it from is incorrect on the eaton unit what other scenarios are out there were I would have to change the posi unit to go to 3.55 gears. Any help is much appreciated. Thanks Erik

If they didn't use a ring gear spacer then you do not have to change the posi. It is the correct one for the 3.55 gears. A 4.10 gear will not fit on the 2 series differential in the 8.2 10 bolt unless a ring gear spacer is used.

I am not very knowledgable with gear ect. but in looking at your responce does this mean that it probably will not work out? If they did not use a ring gear spacer what other option is there to get the 4.11's to work in the axle. Would I have a better chance getting 3.73's to work vs. 3.55's. Sorry I sound so dumb I just want to make the correct decision.

A ring gear spacer is used to install a 3 or 4 series gear on a 2 series differential. If you have a 4.10 gear and a spacer was used then you probably have a 2 series. You can install a 3.55 gear on the 2 series if you use a spacer, but that is not the best way to so it. If you have a 4.10 gear and no spacer then you should have a 3 series differential. You can install a 3.55 gear on the 3 series with no spacer. That is the way it was intended to be. There is no 4 series differential for the 8.2 10 bolt.

Thanks very much. Erik