GSL LSD Swap help
 

Hey guys back again, fixing my 7 up is halted since the weather is full of snow and my schedule is tightening. Was wondering what I'd need for a first gen lsd swap, can anyone help me if I'm missing anything, I'm trying to get an 83 GSL rear end into an 85 GS, I need
- The whole rear end, axles, discs, and diff
- new E-brake cable
- new brake lines for rear discs
do I need anything else? And if it's a GSL I can keep my 13" 4x110 wheels, correct?

Any help is appreciated, thank you

Brake proportioning valve.

I think the driveshaft flange might be different.

Okay possible driveshaft flange and brake proportioning valve, are the suspension components the same?

yes

Sir Surr - Suspension is the same between a drum brake GS and a disc brake GSL.

Qingdao - what and where is the brake proportioning valve? I am also working on a drum to disc axle swap and didn't know about this. I'm putting in a new axle and GSL-SE brakes on F/R (already have the bearings / discs / calipers / brackets / dustshields / soft lines). I take it there's a prop.valve up by the master cyl?

yes

Just found these Master Cylinder and Brake Proportioning Valve part #'s in another thread listed by year, if that helps anyone. It'll help me.
https://www.rx7club.com/1st-generati...-valve-963266/

1979 P. valve 3591-43-900
Master 8871-43-400A


1980 P. valve 8341-43-900
Master 8980-43-400

1981-82
S & GS Models
P. valve FA07-43-900
Master FA07-43-400

GSL Model
P. valve FA07-43-900
Master FA18-43-400

1983
S & GS Models
P. valve FA07-43-900
Master FA07-43-400

GSL Model
P. valve FA48-43-900
Master FA18-43-400

1984-85
S & GS Models
P. valve FA07-43-900
Master FA07-43-400

GSL & GSLSE Models
P. valve FA66-43-900
Master FA66-43-400

The master and proportioning valve seems to be the different. Drums use more volume than discs. So you'll end up tearing through some rear brake pads (at best) if you don't swap these parts. At worst you'll have rear brake locking issues.

When I switched to disks from drums I did not change the proportioning valve, seeing how they're the same 81-82, or master cylinder. For some reason I feel like I'm getting less braking in the rear than I should.
The car has done track days and autocrosses without issues so far on cheap all season tires. I would think issues with locking would have shown up when I did a few wet track sessions a few years ago.

On drums the proportioning valve holds some pressure so that the full volume is not needed to engage the drums on every press of the pedal. It may cause pad drag on disc brakes but it could be minimal. Also the pressure required for drums may be different that disc so the balance of the pressure provided by the proportioning valve may be a factor.