ive looked through the archices on se swaps and im wondering if its possible to just swap out the diff, axles, rotors/calipers, ebrake cable and all rather than pulling the whole rear end if both cars are from the same year. 84/85 have big axles correct? should there be any issues?

 

You can swap in a GSL diff, slight change in gear ratio from 4.1 to 3.9. All the other parts need to be from an SE except the brake cables.

 

Exactly, so why not swap in the whole diff? It's sooooo much easier. And you still need SE brake cables.

 

im trying to ship an se swap but shipping prices are crazy and id figure all the parts should fit into a gsl rear end, providing i provide the axles, rotors/calipers, diff and wheels and also the front suspension. Im just trying to get around using frieght. I know if i can make it smaller and in pieces i can save the guy a whole lot on shipping.

 

yes.....if its an 84/85 you can swap every thing from housing to housing.

gsl and gsl-se cables are the same,

 

there are a couple options now.

1. every 84-85 disc brake axle housing is the same, the gsl-se has different rotors, calipers and axles, but the housing is the same.

2. Re speed makes an adaptor that lets you put disc brakes on a drum rear housing. you'll have to double check to make sure they have a gsl-se brake version, as the 12a and 13b might be different.

3. the early gsl-se's are 4.09 geared, but midway thru 84my they switch to the 3.9. the chassis number and date they switched are in the parts fische.

 

Man, I can never get a definitive answer for gear ratios for the 1st gen. My John Matras RX7 book, shows all 12a RX7s had 3.909 rear ends, and the GSl-SE had a 4.076 final drive. Then I see Mazdatrix websites list all different oem gear ratios, 4.11, 3.909. I have an 84 and 85 RX7 brochure, it lists all GSl-SE's as 4.076 final drives. They also show the 84 12a RX7 as a 3.933 final drive and the 85 as 3.909. Also, I have mutliple sources that can't agree on tranny ratios. I see some sites list all 12a RX7's have a .825 5th gear, some say that 84-85 have a .807 5th, and GSl-SE's have a .711 5th gear. What is the truth?

 

yeah the 5th gear ratio's are all screwed up! the listings are all over the place, and i think there is a typo in the FSM...

just from experience the 12A is the short .825, the 84 gsl-se gets a .758 and then the 85 gets a .711

i think you could look it up in the parts catalog, but i haven't and its a little tricky cause they don't list the ratios, just part numbers, but now that i'm looking there are 3 different 5th gears. 12A, gsl-se up to june 84, and then after june 84

the rear end ratio's are much much simpler, if you look in the parts catalog, they actually just list the ratio's. i actually have confirmed that with reality too, the gears are stamped with the part number

 

So my 85 RX7 GS should have a .825 5th gear, and a 3.909 final drive?

Sucks, I just picked up a clean GSL-SE rear end, I don't know what year it's out of, I wonder what ratio I have.

 

thanks for the info guys! time to pull everything off.

 

The differences between the diff and 5th gear ratios are very minimal. For most driver's, they won't even notice any performance difference, don't sweat it. If your buyer has a GSL diff, just send all the bolt on parts from the diff and the front struts. Buyer does need to have and 84/85 lsd diff for this to work.

 

I dunno about that, a .825 w/4.07 would spin about 700rpm more at 80 than a .71 5th and 3.909 rear.

700rpm is very noticeable, especially with exhaust....

 

well the 3.9 vs 4.09 is the same difference as the height of the stock tires, 12a vs gsl-se. so if you have an 84-85 12a vs an 84 gsl-se, 1-4th are the same, and 5th is a little taller in the SE

if you have a late 84 SE, 1-4 are taller due to the 3.9, but its not noticeable, 5th is pretty tall, but it actually puts the SE engine right at the torque peak @60ish