Rear Ends?
 

OK RX7 GSL, I need to find out if its a standard rear end or a LSD. from what I have read I am getting a mix of answers and the Drum brakes on the back don't mean it has a standard rear end if its in a GSL model. So what are the good ways to see if it is one or the other?
The main reason I am asking is because I will be changing the rear end grease as well as the manual trans grease and I want to make sure the right stuff is going in since LSD rear ends need an additive. Also what fluid brands and weights do you recommend?

GSL's had rear discs from the factory, and a LSD... seeing as that was 30 years ago, who knows what is in it now. The easiest way to tell is to jack up one side of the rear axle and attempt to turn the wheel that is in the air. The only other way is to pull the fill plug off and get a good look in there with a light (this method requires knowing what you are looking for as far as open vs. clutch packs.

I use valvoline gear oil in the trans and rear ends (with ford lsd additive for the limited slip), and have had great success, I have a few 5mts that are well over 250k abusive miles.


Isaac

if its drum its an open diff if its disk its a LSD.

The LSD also has a sticker on the rear pumpkin stating it is limited slip. Of course, it could be gone by now.

I have a drum setup with limit slip

Ok I guess I'll hack it up and see what I have then. Ill try one side first.

stock for stock.

If memory serves me right, I believe that GSL's have LSD but they carry drums with the 4x110 lug pattern. GSL-SE's have LSD's with disc brakes with the easier-to-find-wheels-for bolt pattern 4x114.3. Don't quote me on that though, I could be wrong.

GSLs have disk brakes...

The GSL-SE's do, but I'm 99 percent sure that the regular GSL's run drums...

and your 1% right. my car got a GSL rear end swap and its disk with 110 mm bolt pat GSL have solid rear disks where SE's have vented rear disks

I stand corrected. I could have sworn that I've seen an LSD that was on drums before. Maybe they had just swapped out the pumpkin on a drum car.

that is very likely. the only problem with my GSL swap is i cant find the other hand brake cable so i dont have a handbrake.

Redline MT-90 with a little Lucas additive works great in the TRANSMISSION.
I DO NOT run synthetics in my GSL Limited Slip rear end.

GSLs most definitely do have 4wheel discs from 81 on..

Agreed.

It's a clutch disc limited slip too so to see if you have a LSD put the rear on jackstands and turn one wheel forward. If the other turns forward too it's a LSD. If the other turns rearward it's an open diff.

Ok so just got it jacked up and checked the rolling of tires it's a standard or open differential. So I guess no additive needed. I was looking at some 80/90w sinthetic Mobil One brand. Any good or bad info on using synthetic instead of Dino guts for oil?

Ok so this is a bit strange then from what you guys are saying. Mine is an open diff. with drum brakes and its a stock GSL model 1983. I also had a 1982 with a similar set up, not sure of the rear end but it was drum with GSL package. So the disc brakes must have been on the SE package. Is it worth the time and expense to find a SE model and swap the rear end out for the disc and LSD. What are my advantages or disadvantages in doing this.

Synthetics are good, I run syn fluids in everything but the motor. But it is personal choice in the matter. Oh and yea I converted my drum rear end to limited slip.

The GSL-SE has a 114mm bolt pattern while the GSL has 110mm. If you want a limited slip and don't want to convert the front to 114mm also, then find a GSL limited slip.

All GSL's came with rear disk and limited slip. If you have drums and a GSL, then someone swapped it.

i just swapped my GSL rear into my GS and the GS into my GSL roller :D

Agreed!

Someone could have blown up the original rear / axles, etc.. in your GSL and the need to get the car back on teh road was more important than putting proper replacement parts in there. So they found a junkyard drum rear assembly and swapped it.

You would do best by swapping a GSL rear assembly back in. And rebuild it beforehand.

You do one stripe burnouts, right?

also the LSD could be knackered if it is you may be able to slip the diff. the only way to see if its a lsd without tearing it apart is to jack both back tires up and turn them. if they both turn in the same direction you have a lsd if they turn in oposite directions its an open diff.

Good God, thank you!!

I haven't heard of a GSL trim without rear disc brakes from the factory when it rolled onto the showroom floor.

As far as I know, it stands:
81-83
S - Small bearing drum open
GS - Small bearing drum open
GSL - Small bearing disc LSD
84-85
S - Small bearing drum open
GS - Small bearing drum open
GSL - Large bearing disc LSD
GSL-SE - Large bearing disc LSD 4x114.3

There are some differences in driveshafts (83 being the issue year), but I'll just leave it at that for now.

If you have a 3 lettered trim car without disc brakes in the rear end, you've had a swap for sure in the car's lifetime.