Bought a diff after paying 400 to install it did not fit it was for a small axle car. I have a 1985 rx7 gs open diff rear with drums. I heard a miata 1.8l diff will fit but are all miatas large diff or they come in small and big diff also? Thanks

 

All Mazda 7" 1984-up are 26 spline.

 

all of the 1.8 miatas are big axle, 1994-2005

the 1.6 miata uses a different diff, which will not work in anything

 

Im some what confused. The miata pumkin i remove and will fit right into my gs differental? Will this part clear and fit? Photo attached under and circled. Just dont want to waste more money. When i get it i remove the bolts and it will slide right out ? Cuz on the first picture it looks like half the pumkin is stuck inside. Sorry for being such a novice. Thanks for the help

 

The Miata third member housing has mount cast on the side for a brace that connects to the transmission - that is the thing you circled

Typically the way a Miata 1.8L rear end is used for an RX7 is to swap the internal parts into an RX7 third member housing. So that is the Ring, Pinion and Differential (if Miata differential is better than the one in the RX7). The tech will need to use the pinion spacer from the RX7 housing (not the one from the Miata), a new crush washer and Pinion Bearing. Side bearings should be inspected and replaced as needed.

I have never attempted to use the Miata housing as is.

 

The Miata housing will bolt right in and none of that stuff is in the way. All Mazda 7" have the same bolt pattern to whatever the thing bolts into. I have bolted truck front third members into RX-7 rearends and FC rear housings are an upgrade for the breakage prone Miata ones.

The driveshaft, however, will not bolt up.to the Miata's flange. (Just to be perverse, it looks like the Miata might use the same bolt pattern as FC, while a 1.6 Miata driveshaft bolts up to an '83-85 RX-7, which would be great if it wasn't about four inches too short)

You can use the Miata DIFFERENTIAL as a bolt in. Not the whole third member as an assembly, without swapping the flange. I know someone with a Miata with an FC limited slip, and I know someone with an FC with a Miata limited slip. Why? Because you get your parts where you can find them...