the turbo FCs had a 4.3 rear end right?

will one drop right into mine; an '88 SE model.
im looking to upgrade my diff.

 

umm.. i think there 4.1. and dont just upgrade the diff. its way to much work. do complete subframe change over. its too easy. but search. cuz this subject comes up alot.

 

No and No.

The Turbo models in the USA came with a 4.1 rear end. The same gearing as the 88 SE manual transmission model came with.

However the Turbo differential is a 8 inch gear and differential, while the non turbos were only 7 inch... which means it will not fit without using the Turbo differntial assembly, which would require turbo half shafts, and a custom driveshaft to work on a non turbo car.

 

However, if you DID have a 4.3, you could drop it right in, right?

Because if it was a 4.3 then it must have been out of a GTUs w/ an LSD? Which would be non-turbo...which would be a direct drop-in.

Someone please correct me if I'm wrong..

 

"GTUs" is 4.3 and will fit. rare and expensive.

 

dont you have to use the gtus half-shafts also?

 

no they are the same as all non turbos. all 7" ring gears fit the 7" housing and half shafts. chances are, you don't have a 4.30:1 LSD center section unless you paid $$$ for it.

 

Yes sir you do. You need the halfshafts because they are different lengths.

 

not that I know of, where did you hear this?

 

Autos came with 3.90's(unless it was conv, then 4.10), 5spd cept for the GTUs came with 4.10's and the GTUs came with 4.30's

 

Not quite... as covered in the options and standard features sticky at the top of the page:

Manual tranny coupes (turbo and non turbo alike) came with 4.1 rear ends (except the GTUs model- not to be confused with the GTU).

The 89-90 GTUs model came with a manual tranny and a 4.3 rear end (on a 7 inch differential).

Auto tranny coupes came with 3.909 rear ends.

The 88 vert came with a 3.909 rear end regardless of tranny.

And the 89-92 vert came with the 4.1 rear end regardless of tranny.

And as far as the Turbo and non turbo rear ends. The Turbos (and FD) came with a 8 inch differential and gearing, while the non-turbos came with a 7 inch differential and gear.

 

confusing isn't this?

who really knows the facts?

anyways, I've been diggin around on this subject too and

suprisingly the Racing Beat Catalog shows that all GTU models from 89-91 including the GTUs had a 4.375 ratio. Was that a typo?

This is what it shows in the racing beat catalog:

Rx7 1986-92 NT, Auto 3.909
Rx7 1986-92 NT, Man, Ex GTU 4.100
Rx7 1989-91 GTU 4.375

notice that for 86-92 NT 5 speeds it shows 4.100 except for the GTU models which seems to indicate that the GTU did not come with a 4.10 rear gear ratio.

Then the next line shows 89-91 GTU having 4.375 ratio and there is no indication of GTUs models probably because all GTU models including GTUs have 4.375 rear gears.

Another interesting fact pulled from the Factory Service Manual that may be helpful to people: the 4.3 rear ends have 43 teeth on the ring gear and the 4.10 rear ends have 41 teeth. The pinions all came with 10 teeth so you see the 41/10 = 4.10 and 43/10 = 4.3

Oh, the FSM also says that the Turbo Rear ends have 8" rear ends vs. 7" for the non-turbo cars. You were correct when you said its hard to bolt the Turbo rear end into a non-turbo because there are many differences. The driveshaft bolt holes are wider and the halfshalft flanges are different too and also the halfshaft lengths are different. It probably is way easier to change the whole rear subframe with halfshafts and all, but you will have to still redrill your driveshaft flange to match.

Its much better in terms of effort to get a LSD rear end from a non-turbo car.

Dave

 

But racing beat is wrong on that. Just read the Mazda info in the options and Standard features thread at the top of the page.