I am looking for a limited slip axle set up for my 85 GS - was wondering if anybody has any input on:

What is appropriate ballpark pricing for a hub-to-hub GSL disc brake limited slip axle assembly from a 12a-equipped RX-7? I found a local wrecker with a couple, and I think their price is high... if it's not I'll suck it up and buy it, if it is I'll try to deal or look elsewhere.

What differences are there between the drum/open rear end assembly and the disc/limited slip setup? I am thinking primarily in the suspension mounting arrangement - do I need to change out additional components going from a GS to a GSL rear end or does it bolt right up?

 

Direct bolt in swap, All suspension mount points are the same. What price is the salvage yard quoting?

 

You will need different cables for the parking brakes setup and different plumbing for the
brake lines. Both fairly straight forward and the parts should be available.

 

I was hoping to avoid influencing the responses by not posting the list price.

Are we talking about hard lines or just the flexible bits at the end?

 

Some hardline differences and flexible line differences. The drums share the end
bleeder with a line running across the axle to the other wheel. The disk have
flexible lines to each disk and changes to the hardline routing because of this.
Drums only have one flexible line that comes down to the driver side of the axle.

Check out this link to the BD catalog and it shows it to you:

 

Factors affecting price will be:

1. Overall condition of the gears and LSD. Is there play? Any grinding/growling noises or history of problems? Does the LSD still work? (Many don't work very well anymore if there is appreciable mileage on the unit).

2. Whether the unit includes brake calipers, rotors and hard lines and if so, their condition (add to the cost anything that will need to be replaced).

3. Where you are located and the overall availability of parts in that area. It's always nice to have several to chose from. If you've already located two units, you're doing pretty well.

For price, I would say you could probably find a serviceable 84/85 GSL LSD rear end for around $150, without the brake parts, maybe a bit less if you're lucky (I gave away or bartered the last two that went out my driveway).

For a decent unit with functional brakes or at least repairable brakes, about $150-$250. $300+ for a unit that's in very good condition, with all the parts and a recent brake job.

Now can you tell us what the junk yard is asking and the condition they're in? This would help us all get a sense of what they're actually going for.

 

Thanks for the link. Looks like the hard line differences are on the rear end rather than the chassis. That's good.

Seems like my feeling that they're listed high isn't out of whack. They're $450 each at the wrecker, 130k on one, 100k on the other (in USA miles). No idea if they have brake parts but my guess is no. The yard has a reputation for being overpriced by 100-300%. I figure they probably paid a quarter that price for the hulks they came in on. I'm not going to take this as an indication of actual value, as they're only worth as much as somebody will pay, and I'm not buying one for that.

 

I forgot to mention, that the driveshaft flanges on the pinion changed in 83, so if you get a pre-83 rear, you will need the driveshaft to match.



$450 sounds pretty steep if you ask me, esp for one in unknown condition. Ide start by searching the "for sale" section of the forum here and/or post a WTB thread, as well as posting a WTB thread in your region specific section of the forum

 

To clarify, the soft line on the driver's side is not the same part between the rear drum version and the rear disk version. IF you order from BD, make sure they send you the right hose. I ordered my hose months before I installed the rear and didn't realize until it was too late that they'd sent me the wrong hose. Luckily you can get this from a good auto parts supplier.

Don't forget the little 3-way joint the connects the hard lines on the GSL-SE rear to the soft line that goes between the joint and the hardlines to the MC. Mine didn't have it, so I had to source it elsewhere.

fm

 

Okay, I can tell you this for certain:

1. I have a '85 GS
2. I paid $250.00 for a complete rear axle assembly (brakes, hard lines, etc.) from a '84 GSL
3. It was a direct swap. Meaning that I did not change any brake lines (just connected new to the old) and did not change the proportioning valve or master cylinder (which many claim is important).
4. It performs flawlessly as-is. I daily drive it. I autocross it (quite succesfully, I might add). It just plain works. The braking balance (front/rear) seems to be perfect.
5. It's worth every penny, even if you have to pay "more than it's worth". The LSD makes the car so much more fun and controllable, and no more drum brakes to deal with.


Good luck man.



.

 

^ agree with the master cyl/proportioning valve thing, many say it should be changed with the swap, but I disagree. Im still running my drum brake hydraulics on my S2 GSL rear and I think the brakes are balanced very well, much better than when I still had drums. I cannot give a fully unbiased opinion though, as Ive never driven a true GSL

 

According to the 84-85 parts catalog, both disk and drum brake models use the same MC/prop valve. I think the earlier models are the ones where they are different, thus should be changed. I have an '85 and didn't change the MC or prop valve either.

As I stated before, there is one soft line you will have to change to go from drum to disk...the driver's side rear line that connects the hard lines on the axle to the hard lines that go to the MC. Your drum brake soft line will not work. Also, make sure your axle comes with the 3-way connector for the hard lines or you're screwed. Mine didn't and I had to hunt for one...I was lucky and found one on a GSL-SE part-out.

And 3x what Kentetsu states. This is easily the most worthwhile upgrade for anyone wanting to get their car around the track faster, and I wouldn't balk at paying what your local yard is charging.

fm

 

I was going to ask about the MC and booster stuff when I logged in but you guys beat me to it haha. Thanks for all the great info.

 

after I upgraded my RX-3 to rear disc brakes with RWD 626 MC, i didnt have any problem with rear disc brake locking up. then i modified the 626 MC rear brake port per whatever I read on the forum, I didnt notice any difference in braking. then finally, for much better braking, I upgraded all of my RX-3's to FB brake/clutch pedal assembly with GSl booster, MC, proportioning valve (front and rear) and clutch master.

My sons 84 GS has been upraded the GSl rear only. no iasues.

 

^ except for autocrossing, this has been exactly my experiences with this. aside from the emergency brake cables, everything bolted right up from drum rear to disc rear - nothing tricky about it. worked perfectly once bled.

 

diabolical1 and Kentetsu,
Are you saying you didn't have to replace the soft line between the MC and the rear hard lines? In my base S model '85, I had to do this...there was no way stock drum soft line would work...completely different connector to the 3-way joint on the axle.

fm

 

i'm 99.9% sure i did not. the last time i changed a rear was on my '84 GS and it was sometime in 2004. what i can say for sure is that the whole thing took me about an hour and a half and i drove the car about 230 miles back to school within a couple days. aside from the brake cables, i didn't need to buy any other parts. so i know for sure there were no lines that required extra attention.

if you're speaking of the line i think you're speaking of, the 0.1% left is simply because i can't remember one came attached on the GSL rear i installed.

 

are you guys referring to the soft line between the hard line and the wye to both rear brakes? if so, they are the same. in fact, you can use the clutch soft line. pre-81 has a different thread pitch so more work is required.

 

Siraniko,
We're talking about the soft line that goes between the axle and the hard line that goes to the MC, not the hoses that connect the hard lines to the calipers. The caliper lines don't need to be changed.

The line I'm talking about is not the same...the end that screws into the 3-way joint for the axle hard lines is different, and the hose is slightly longer (12+ inches, IIRC). The other end, however is the same and connects right into the existing hard line to the MC.

diabolical1 brings up a good point in that some rear end swaps will have that hose already on it. If that's the case, it truly is a plug-n-play deal. Mine, unfortunately, had neither that soft line nor the 3-way joint that connects the MC to the axle hard lines. If you are missing either, you will need to be sure to get the correct line. The line is easily purchased, but the joint...not so much.

My point here is to be sure you're getting EVERYTHING you need with the axle...if it's missing that stuff, plan (and pay) accordingly.

fm

 

Its a much more involved job on an SA thats for sure. I guess on FBs it pretty much is plug and play.

 

I'm about to do this so I thought I'd revisit the discussion.

I got a complete small flange GSL rear end in very nice looking shape for $250 via a want ad on local Craigslist. I named the price I thought would be fair for one in good condition based on this thread, pretty easy deal. No surprise it came from a serial RX-7 owner and rotary enthusiast.

Anyhow, besides the brake cable from the car to the axle, are there any other gotchas or tips for making this job go smoothly? I had "fun" getting the transmission into position and the axle is way heavier so I'll be a lot less effective wrestler vs. that.

Need some advice on parts - RockAuto has several brake lines listed: rear upper, rear lower, rear, etc. Which one? Also, it's a '81 GSL rear end going onto a '85 GS - are there any differences between years on that brake line; should I have a preference between a part listed for the '81 vs the '85?

(yes I have a small flange prop shaft to go with it)