Fat_Tony

Hey, i have a 1984 1st gen that i circuit race and wanted to change the differential from the stock open diff to an lsd.
I know the second gens come with an lsd and was wondering if anyone knew if it would fit into the housing without major machining and if the braking mechanism would easily work back.
thank you.

Pele

iTrader: (28)

You're gonna have to use your existing pumpkin, axle housing, ring and pinion gears... Brakes will remain the same as well. All you'll need is an N/A differential carrier.

I think the S4 GTU and S5 GTUs used the turbo diff.

boyee

iTrader: (3)

why not just put on a gsl or gslse posi diff? should fit right in with no mods i believe and its just as good. also converts to rear disc brakes.

12a79

go wit the gslse it seems to be the strongest for wat i know my friend is running a 245 hp turbo on a first gen diff holding up real good.

Fat_Tony

thanks alot for the advice fellas, i appreciate it.

trochoid

iTrader: (6)

The 1st gens use a 6" ring gear. All NA 2nd gens use a 7", and the TII's are 8" Your choice is a GSL or GSL-SE diff, if you want to keep it simple.

inuissus_cendi

yeah the GSL-SE should swap right in since you have an '84 (they changed between 83 and 84) plus you get quicker gears. GSL has the same gear ratio as any other first gen.

SparkienSuggah

the gsl-se rear end was also heavier wasnt it? a big consideration for the track.

Fat_Tony

thx for the insight fellas, i think im going to go with the gsl-se diff, cause i get the rear disks as well that way and its an easy swap.
i appreciate the help.

kevinbtz

iTrader: (4)

Is it heavier because of the vented disk brakes?

inuissus_cendi

I think the major weight change was just from the pre-'84s to the '84-'85s. Don't think there was a significant weight difference between an 84-85 GS rear, 84-85 GSL rear or 84-85 GSL-SE rear. I remember reading on here that there was a roughly 50 pound increase in the weight of the rear end between 83 and 84. If that's true then the best swap would be to a pre-84 GSL diff. It would be the lighter model and still be limited slip. You'd have to do the whole thing though not just the pumpkin.

jasrx

i run a Guru Torque Biasing Differential in my s3 rx7
i have around 250+rwkw
GURU Racing has produced a automatic torque biasing differential, it is designed to prevent loss of drive to wheels without locking together, while still applying some torque to the slipping wheel.
This progressive action applies all remaining torque to the wheel with the most traction, which is the best design to gain maximum grip under varying track or surface conditions, also leading to improved controllability and cornering compared with a standard LSD unit.

T_Racer

iTrader: (1)

The gsl-se is heavier because of heavier duty axles. The axles are larger in diameter, hence the weight. They are more robust, switched to them after going A prepared in Auto-X. Stock Torsen, rebuilt, good unit, easy replacement, and pretty good lsd for cheap.

Cheers,
Travis

peejay

nope. 1st-gens use the same 7" that the RX-2, RX-3SP, '94-up Miata, and many trucks used.

The FC also uses the 7" but with a different pinion length. Differentials are interchangeable with 7" Miata and Series 3 RX-7 but the gearsets and housings are not.

peejay

the GSL-SE uses the same damn sizeaxles as all other Series 3 RX-7s. The only difference between a GSL-SE rear and a normal S3 rear is the length of axle outside the bearing, which ironically makes them weaker. (Reportedly the -SE diff has fewer clutches than the standard GSL diff for better driveability) And of course the normal difference between disk and drum, and the -SE specific brakes.

j9fd3s

iTrader: (3)

the parts that are different between the 84-85 gsl rear end and the gsl-se rear end are the following

ring and pinion (thru november 84, then its just a normal 3.9)
axles (longer, different wheel bolt pattern)
brake rotors
calipers
backing plates
e brake cables

i am looking at the parts fische while typing this....