OK I thought I knew what I had to do to put an R200 3.90 in my 71Z,but now I'm not so sure.I just bought a Diff. from a guy that also had it installed in a 71Z .He tells me that I don't need to change anything to install it (no mustache bar,half shafts,ect).After taking it home I decided to open the cover to make sure it was a 3.90, which it was ,it was stamped 39.10.Ok,so if it is an R200 how can it fit a 71 Z without changing mustache bar , cross member and half shafts?:cross-eye

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If nothing has to be changed (according to him), you might want to check that it is in fact an R-200, it could be an R-160 from a 510 that had the 3:90 from the factory, or an R-180 from either a 200SX or 4x4 truck.

If your rear crossmember is straight, you have to change it. If it is curved, you dont have to change it.

Do a search for R200. I posted photos of the curved crossmember in another post.

Thanks Guys, I'm begining to think it's an R180 with 3.90 gearing.If it is, is there any reason I shouldn't stay with it rather than going through the r200 swap?:cheeky:

Oh, I do understand that theR200 is stronger and can be upgraded to LSD.But other than that,I mean I've got an L28 with an N47 maxima head and 83 5 speed.will this combo likely break my diff?

The 180 is fine with darn near anything an L series can put out. The only time you'd need the R-200 would be with an RB or V-8 swap.

The 180 can be upgraded to a LSD as easily as the R-200, and the Quaiffe unit for the 180 is a couple hundred cheaper to boot.

Great!Thanks for the info.