I need a pumkin that i can install in my 85 rx7 gs with drum brakes. Alot of people telling me a miata diff will work but alot are saying ill have to shave some part off to fit the watts linkage. Then im hearing also that the miata diff flange wont bolt onto the rx7 drive shaft. Please help im just trying to get a pumkin and swap it in anyone that will fit a big axle 85 gs rx7. Thanks. I already spent 400 on a small axle pumkin that dont fit aint trying to waste any more money on wrong parts.

 

If you want something that requires NO modification, then ANY 1984-1985 pumpkin (center section) is the only choice. I'm not sure how much you made that evident in the other threads.

A small axle pumpkin is not a direct fit for a 1984/1985. Not sure who told you that was an option.

 

I just re-read your other thread and the answers that were given are correct to your question. What you didn't say is "Direct fit without any modifications and only installing the pumpkin in it's entirety" and/or "without making changes to the driveshaft". I think the answers you got were pretty start forward and a learning experience about the difference between parts. With this said, taking answers and logically applying them to the task at hand are important.

I don't want to sound harsh. We are here to help. Before making another purchase, bring it before this group and we can tell you if it's the right part that you need/want.

https://www.rx7club.com/1st-generati...e-smh-1159043/

 

The third member out of any RX7 will bold up to any RX7 rear housing but there were changes over the years.
Drive Shaft Flange:
79-82 are the small flange - bolt holes are threaded and pattern is rectabgular
83-85 are the large flange -bolt holes are not threaded and pattern is square
Axles:
79-83 these are the smaller axles.
84-85 these are the large axles - all are the same whether car has drums or disks on the rear
Whats the difference? The inner spline counts are different. Axle diameter is different, Axle bearings, retainers and seals are different
GSL/SE axles are longer out side of the axle bearing than the ones used in the GS (drum brake) and GSL (disk brake) models in 84-85

Options
Drive shaft flanges can be changed out. So a miata flange can be replaced with the right one for your RX7
Side gears in the differentials can be changed between the small axle differentials and the big axle differentials

You were told by PeeJay that the 1.8 Miata housing you own will fit your rear axle housing so take it to the bank. He knows his stuff. If you do that, your mechanic will need to swap the drive shaft flange for the RX7 flange you should have.

 

If I understand this correctly you can use all 7 inch differentials in both small and large axle applications because the side gears can be swapped correct?

 

Just find a 84 to 85 Rx7 pumpkin.

 

I would prefer a Miata Torsen.