patmac6075

iTrader: (26)

I have an opportunity to pick up an '85 GSL rear end to swap into my '83 GS. Couple of things....#1 Will the drive-shaft just bolt up? #2 How difficult is it to hook up the e-brake? What additional cables do I need. #3 I've heard conflicting information on whether or not I need a proportional valve (I think that's what it's called).

This also leads to a larger question.... What is your opinion on this swap? Is it better to do the entire swap, or is it better to just swap out the pumpkin/keep the drum brakes? Obviously, not in this case because the large axle/small axle, what I want though, is the limited slip diff. I've heard there is no substantial weight savings going to disc brakes, there in not a mechanical advantage in stopping power, and the drum brake e-brake is simpler and has better holding power. What's your opinion?
Thanks

patmac6075

iTrader: (26)

Bump....Nobody's got an opinion?

Kentetsu

I swapped a '84 GSL into my '85 GS. Did not change the Master Cylinder, or the P-valve. I love the upgrade, the LSD is awesome, and my brakes work like a charm.

Go for it, just bolt it in and enjoy it.



.

OneRotor

iTrader: (3)

Is your car an early or a late '83? If it's an early '83, you may have a small bearing (S2) rear end, in which case you'll need an S3 ('84 or '85) rear end, as the input flange is different. Other than that, bolt it up and enjoy.

Kentetsu

Or, I think you can just use the drive shaft that goes with the rear end...

Speeder165

iTrader: (7)

The flange to the stump can be pulled out & changed to mate to a different driveshaft. I ran across this problem awhile back. Easy to do. Took maybe a minute or two after I had unbolted the driveshaft.

OneRotor

iTrader: (3)

You don't ever want to do this. There is a crush collar that sits around the pinion shaft that allows you to set pinion lash/mesh, and when you remove the flange, you must replace this part to ensure proper gear mesh.

I found out the hard way that someone had removed my flange at one point. Launched the car @ 5500rpm on some rather old 185/70R13 BFG all season radials, the crush collar was smashed by the gear separation force (two gears, meshed together, will attempt to push away from one another when a torque is applied) and it popped my front diff seal. Just get the proper driveshaft. It will save you a ton of headaches in the future.

Speeder165

iTrader: (7)

Haven`t had any problems with mine but then again, I don`t launch my car at 5500 RPMs either! Luck of the draw perhaps?

mazdaspeedrex

It's the same driveshaft from at least 81 to 85. I once swapped an 85 GS shaft into an 84 GSL-SE. Now I have an 81 shaft and axle in the 85 GS. I had to swap park brake cables since I did go from drum to disc. You just need cables from the disc brake car. Everything else bolted right up. And there is a substantial increase in stopping power from drum to disc. Why do you think front brakes have been disc since the mid seventies. I just worked on a 72 Mustang with drum all the way around and it didn't stop for anything.

patmac6075

iTrader: (26)

Not an expert on this, but my understanding is the front brakes do like 80% of the load while stopping a car, hence the advantage ( not disputing disc brakes have a tremendous advantage in front) in front. I would even agree that in the rear discs carry an advantage.....But if they are only handling 20% of the load, is there a noticeable difference? Do they just "lock-up" earlier (Today's cars with ABS can adjust for this)? And lastly, doesn't the Drum set-up work better as a parking brake?
Not looking to start a war......just looking to get a better understanding from the experts.

mazdaspeedrex

The main reason I prefer disc on the rear is there are less parts to break. The springs on the drum system will stretch and weaken over time. The "self-adjusting" park brake doesn't "self-adjust" very well and if you want the same pressure as new brakes you have to adjust it yourself. As long as the disc caliper is in good working order you never need adjustment. As a mechanic, I see more problems from malfunctioning drum brakes than disc. They all wear out but I see broken spring hardware and leaking wheel cylinders more often than bad/leaking rear calipers.

wankelnewbie

iTrader: (2)

I'll second this^^. Pad replace = 10 minutes, shoes replace= an hour, then another 2 trying to figure out how to roll back the parking brake! (don't ask where I get these figures!)

Discs do stop better and have a more linear curve when you plot braking force against pedal pressure. Seems like a lot of people on the forum do this without a prop valve. I mean maybe the difference in the response curve equals everything out? I'd go ahead and do it and if you feel like there's too much rear brake just throw a prop valve in? I mean it's not more than a days work.

Kentetsu

A lot less fade with disc brakes too.