Datsun Roadster Forum-311s.org

A NOS 4:11 ring and pinion, that is As many of you know, I have a love hate relationship with my 4:62 gears. Love them for play time, hate them for getting to a place to play. I’m hoping that the 4:11’s will be just the ticket. They might hurt me on the autocross course, but so far I don’t have any problems accelerating out of the slow corners, but sometimes hit the rev limiter on the faster portions. If these keep me in the 4 to 6K rpm range they may even help. Definitely going to make getting places a little more relaxing.
I’m just a little concerned though because the part number on the box does not coincide with what I think it should be. However all the critical measurements between the new set is within a couple of thousandths of my old 3:70’s with the exception of the ring gear thickness. The 4:11’s are about 3mm thicker. I know some gear sets call for a 4mm spacer but I don’t think the 4:11’s do. The box which may, or may not, be the original shows part number 38100-25900.

It could be for the trucks, they fit in the housing but you would the flange from a truck differential to make it work.
Dave

The csp311 came with 4.11 as standard, 3.89 was an option. Mine will be comng out at some point and 3.7 going in.

Mystery solved! The part number from the Datsun Competition Catalog is different than the one I referenced in the Datsun Roadster Book.

Find the right shop that knows how to setup the differential, otherwise it may self destruct. Because the housing is aluminum it can have the carrier caps spread wide during setup and then it will not fit back into the axle housing.
Dave

Thank you Dave, I definitely intend to take it to an experienced differential shop.

I might add, find a place that has the adjustable spacers that are installed where the carrier bearings normally are ...it's easy piesey then, a tech just mics the thickness and adds shims to give that equivalent, Subaru/ Isuzu ( ya defunct) has- uses them otherwise its a crapshoot it is perfect or not