ok. heres the quick question. got a 84 gsl lsd rear end to put in my 80. was told the brake lines arn't the same, no problem have the other car. my main questsin is do i need to change the master to? and another question, what is the gear ratio on a lsd gsl? i see the gsl-se are 4.07. are the plain gsl's that or are they the 3.90?

 

1979 and 1980 have different threads than the 1981-1985. They have course pipe threads. You can get SS line from Mazdatrix that will give you SS front lines and the one SS body line in the rear that has the 1980 thread on one side and the 1981-1985 thread on the other side.

I think it is 3.90.

You don't have to change the master cylinder. There is an excellent writeup on how to change the 1979-1980 to the 1981-1985 brakes and lines. You have to change the master cylinder, the hard lines and use the rubber lines from a donor car. It can be done. I have a 1985 rear, the master cylinder with proportional valve and am considering swaping out hard lines and everything. That is if my car stays together long enough.

 

I dont know about the different thread sizes, but do know you dont have to change out master cylinders. If you have it I would, because the MC for the disc gives more pressure to the back brakes. The drums dont need as much pressure as the disc, but the brakes will stil work with the drum MC.

 

There's two ways to do it:
1) get thread adapters from the '80's course to the '81-up fine for the flex line to the rearend
2) replace the entire braking system with the later model stuff; front brakes (in your case, I think you can just swap calipers - I have a '79, so the whole strut had to change), rear axle, MC/prop valve, and hydraulic lines.

(2) is actually easier than it sounds. I did it all ina day. The toughest bit was breaking the fittings loose, the second toughest was snaking the right front hard line through the engine bay.

Write-up here.

 

now where to get the thread adapter is the question for #1. I have heard of people making them but where to actually buy one............

 

http://www.wankel.net/~krwright/cars...ds/brakes.html

Looks to be a complete answer to rear-end swap questions, although at some point I remember reading that a master cylinder swap is unnecessary; only the proportioning valve needs to be changed, because the rear discs now require a different proportion of the brake fluid than the rear drums did. That being said, I snatched the master cylinder off of my -SE donor when I had the chance =p.

 

That's my site, referenced in my previous post.

You don't have to change the MC only if you're swapping from 81-up GS drum to 81-up GSL disc rear. The '79-'80s have course threaded hydraulics instead of the 81-up fine threads, so if you do both ends you have to do everything.
The alternative is to use an adapter on the rear flex line to hard line. dunno who has those.

 

hey, thanks for all the info...
Frankenrex......... you've got a nice site there.

 

Thanks, just trying to get all the crap I've done to the car down so I don't forget what I did
Figured it might help someone else sometime...

 

When I did my swap I didn't swap out my M/C or my proportioning valve. The brake bias seems pretty close to neutral, maybe even a touch rearward. What I did was make an adaptor out of a new hard brake line with the fine thread on the one end and an old coarse end from the '79 axle I took off. After that it was easy to use this short piece of hard line to adapt the fine thread lines on the axle to the coarse thread rubber line going to the M/C.

All you need is a short lenth of hard brake line, 2-3 inches and a flare tool.

 

Kevin Wright, hmmm. You were on the old mailing list back in the day? Sorry just feeling nostalgic.

 

Which old mailing list? The "big list"?
I'm still on the SA22C list, formerly known as the FB list, and the DFW-RX7 list for North Texas rotaries.
And a bunch of non-'7 lists and groups - I get so much email it's not even funny... Gotta pare back on the hobbies and interests a bit, I suppose.

 

You don't even have to go that far, though I do like your solution because it's easily reversible (I'm big on being able to go back the way it was if necessary).
You could actually cut the flare off of the '80 hard line where it connects to the rear flex line, remove the course fitting, put a fine fitting on, then re-flare the tube. There should be enough slack to allow this.