i have a gsl rear for my 82' and i was wondering is it the proportioning valve i need from a disk rear or is it the MC that i need?

 

The proportioning valve

 

thanx

 

I do not know if there is a difference with the proportioning valve BUT I do know when you replace the drum brake rear with a disc brake rear you need the master cylinder fron a disc brake car. The disc brake master cylinder is a larger bore than a drum brake. The disc brake rear cylinders require more fluid than the drum brake rear. When I did the same change it was to a road race car & I took out the OEM proportioning valve & implemented a Wilwood manual valve.

 

I did this conversion when I installed an 85 gsl rear end into my 79. I personally did not change the master cylinder, and seems to work fine for me. I do not know if I am correct in doing it this way but I have not noticed a difference.

 

The easy way to figure this out for sure is to look at the part numbers listed for the non-gsl vs the gsl cars. I think you need to change out both.

Rear disks take less pressure than drums. Without changing out the proportioning, more force goes into stopping the rear wheels than ideal. This can lead to:

Rear locking in emergencies (which isn't safe)
Premature rear brake pad wear
Longer stopping distance than optimal

Not changing the proportioning may not be something you'd notice under normal driving, or maybe even ever, but it's definitely not the best thing to do.

 

The proportioning (bypass) valve is different for the disk brakes. Different part number.

The master cylinder is also different. I would strongly recommend replacing.

 

Really? When I swapped my 85GS rear for an 84GSL I didn't change anything else. Brakes work great (and I do mean great), so I'm not sure if I should be worried about this....

 

If your gonna do it, do it all. Better to do something once, than twice. Or better yet, never again...

 

Just imagine how good they'll be if you finish the job.