-xlr8planet-

iTrader: (3)

Hi guys.

Is possible to install an LSD from another model into a base model without swapping the whole rear end?

I need help on sevens...

calvinpaul

iTrader: (2)

I'm not sure, but if you swap the whole rear end you get the upgraded shocks, and disk brakes, and the bolt pattern. It is defenently better to swap the whole thing.

Rusty Shackleford

i want to know that too because that way i can keep the rims and shocks and springs i have already

85MarkRx7

Yeah I was going to ask the same question I want an LSD unit my friend has an 83 GSL I have an 85 base I want to swap just the LSD from his into mine is that possible.

82transam

iTrader: (18)

ok, lemme try to clarify this, I'll do my best as it gets a little confusing. first off, calvinpaul, you're reffering to the GSLSE rear end, in which case the bolt pattern and brakes differ, as well as having LSD. You can swap a SE diff into any 84/85 rear end. Any 81/82 diff is interchangeable with another 81/82, and any 83 diff will fit into a another 83's housing. This is all reguardless of weather its an open diff going in a GSL housing (dunno why you would) or a GSL diff going in a S/GS housing. Now, the axles on all 81-83 cars are the same, but the driveshaft flange is bigger on the 83 (the same flange that the 84/85 cars have) so if you were to put an 81/82 diff into a 83 housing you would have to either change flanges, or get the earlier driveshaft. You cannot put a 81-83 diff into a 84/85 housing because 84/85 cars have bigger axles, and thus different housings. Hope that helps, its kind of confusing.

82transam

iTrader: (18)

oh and I should also note a few more things, any 84/85 rear end is interchangeable, that should include the SE as well. One thing to remember is that all non SE rear ends are 3.909, and SE rears are 4.11 (or was it 4.10...) honestly if i were you I'd try to find a whole GSL rear end to swap in, the rear disks make quite a difference in pedal feel, but I guess if you're having a hard time finding the whole thing swapping just the diff is better than nothing....

Rotor13B

Then how come the 82 diff bolted right up to my 83 driveshaft? I shattered my ring gear on my 83 diff and had to replace it with a 82 diff to get my car home. I didn't have a problem putting it in accept for the axle housing carrier was bigger than the diff housing carrier. Which left only the bolts on the diff to hold it in. Worked in the a pinch though.

31rx7

I have done this swap. First thing: 84-85 Diff takes larger diameter rear axle shafts. You can not swap the later diff into the earlier cars or vice versa without swapping axle shafts. The 79 - 83 diffs are all interchangeable.

If you only want to swap the diff, it is a relatively simple matter to pull the axle shafts, remove the center section ("pumpkin") and swap the diff. Or, swap the entire center section. I would need to research to be sure that the center sections are all interchangeable per the years above.

I can not recall if the driveshaft flanges are different per the above note. Measure first to be sure if you are swapping the entire center section.

I have said this before, the drum rear brakes, though low tech, are just fine for most street and moderate performance driving. The rear brakes don't do a lot of work, so the extra fade resistance afforded by the discs doesn't really come into play.

By only swapping the diff, you save having to swap parking brake cables and master cylinder.

-xlr8planet-

iTrader: (3)

duplicate post

-xlr8planet-

iTrader: (3)

This turned out to be very informative.

Is an LSD for an 80 expensive?

MarkPerez

yes, it can be done. even with drum rear brakes. it's important to match up the years though. say you have an 82 s (base model) try to find a 82 gsl that way you don't have to worry about axles and driveshaft flanges. it goes all the way up to 85. but i can't say about the 84-85 -SE's. a 85s (base) and a 85gsl no problem but don't count on a 85s and a 85 gsl-se interchangabilty. jack up the rear of the car and support with stands, pull both axles and the driveshaft, unbolt the 3rd member(pumkin),,,oh first drain the rearend housing before jacking up the rearend.
it might be a good idea to get a new gasket and a couple of quarts of limited slip gear oil before starting the swap also. once the (old) 3rd member is out use a wirewheel and clean the gasket surface on both pieces, when clean install the 3rd member and use a couple of nuts to hold the 3rd member in place then slide one axle at a time into the housing and when 'seated' place a couple of bolts to hold it then do the same for the other side. when it's all together finish installing all the rest of the nut's / bolts. before bolting up the driveshaft check the 'play' back and forth on each axle. you don't want 'too' much play. but remember alot of the play will go away when limited slip gear oil is pumped in the housing. bolt up the driveshaft and test drive the car. it's a pretty straight forward swap but your going to get very dirty doing the swap.

Snapshot

I've had the "pineapple" or "chunk" replaced 2 times on my 81 GSL from used parts. Never had a problem. Maybe I was lucky, but everything always sinced up. BTW: use Amsoil synthetic in the trans & rear end.

MosesX605

Just a note, the '79 and '80 axle assemblies are basically large paperweights. You CANNOT swap a later model diff into a '79 or '80 housing. So if you have an '80, you need the entire rear housing, diff, axles and brakes. I swapped an '81 GSL rear assembly into my '79 and it was fairly easy. The only stumbling block is the thread pitch on the brake lines. The '79 and '80 RX-7's had a coarse pitch brake line, the '81 and up have fine pitch. You have to fabricate an adapter to mate the fine thread pitch from the newer brakes to the coarse thread pitch on the flexible hose. What I did was hack an end off the old brake lines on the '79 axle and use in and one fine pitch end on a short piece of hard brake line to make a little adapter that will mate the two lines.

Good luck.

82transam

iTrader: (18)

The diff you put in wasn't an 82, or the rear end in your car wasn't an 83, or maybe someone had swapped flanges and driveshafts for some reason, cause 83 has the larger flange, I know this for a fact. Oh and as moses correctly notes, the 79/80 rear ends are totally useless, you must swap to a 81-85 rear axle assembly in order to do anything, so you might as well just find the GSL rear and then have disk brakes as well.

Rusty Shackleford

i thought only an SE had the lsd.......but since i have an 85 that mens i can swap a 84-85 lsd from a gls and a glsse ????

82transam

iTrader: (18)

both GSL and GSL Se's have rear disks and limited slip. The Se has the different lug pattern and a different rear ratio, but both are LSD. And yes since you have an 85 any 84/85 diff will fit in your housing.

alien_rx7

Yup, '83 has a larger flange. I had two '82 diffs and an '83 to compare with to make sure. Also could have been a change halfway in the year but I don't think so.