I have a 1983 GSL w/ a SP 12A.

Should I just keep the stock rear with disk and LSD?
Or should I go with the GSL-SE rear with vented disk and LSD?

I don't care about the change in bolt pattern. They already both have a LSD. The change in gearing would be nice but I can live without it. I don't make enough power to hurt the GSL rear.

Basically is having the vented disks make that much of a difference in stopping power to justify the cost to change over?

 

well id go half and half the GSL-SE rear end. but put the GSL LSD gear in it it has better teeth on it less likely to break.

 

ditto, better clutch packs on the gsl.

 

Is your rear a early 83 small axle or late 83 large axle, if it is the small axle the GSL-SE is going to be significantly stronger.

As for the brakes, you will never need much more at the rear, these cars lock up the rear under severe braking too easily anyway, we usually put in a brake line adjuster to reduce rear lock up (cheap brake bias valve)

 

The rear is an early 83 small axle.

What do you mean by a brake line adjuster?
I will do some searching to see what I can find.

 

Ive gone both ways,and the change in gear ratio is minimal at best.
The GSL has the better LSD,but if its under 200HP and your not beating it,the SE LSD will hold up just fine.I broke my SE LSD's single drive plates,but it took 6-7 years behind a 300HP TII engine to do it.

The brakes are also a minimal improvement as aussie said.They will hold a little better in regard to the parking brake, and they will fill up an open spoke wheel better,but thats about it.With stock size tires,its easy to lock em' up.

The larger axles of the 84-85 cars is always a good thing,but its hardly an issue with an N/A 2 rotor unless your very hard on the car.I had 10 years of rough driving on the 82 GSL rear that I put in my 78 GLC,and it had a torquey little Chevy V-6 in it. No breakage,no twisting and no LSD failures.

 

Thanks for all the help.

The plan is to keep the existing '83 small axle rear. The motor will probably never be over 200hp at the wheels. I plan on going to a 15x7 wheel but not any taller tire. The car has about 175k on it and the motor has 630 miles on it. I plan on rebuilding the trans this year and the rear within the next two.

I never push the car too hard. I will probably take it to a drag once or twice but that is it. This car is my DD and I plan on using it for autocross.

 

Uh oh here's that myth about the "early vs late" 83 rear end's again, there is only one 83 rear end, it has small axles and the large driveshaft flange, there is no supporting part numbers or documentation proving that the 83 had a mid-year change to the larger axles, they are all small axles....
Anyway, I would probably just keep the 83 rear you have in there, which is what it sounds like your doing, the SE really doesn't have much advantage, other than the stronger axles...

 

Well my old 83 disagrees with you, I had a large axle 83 GSL..........I don't care what part numbers you have, I owned one. There's nothing new about a particular model getting upgrades throughout its life time.

 

Mine has a build date of late '82.

 

Then yours if definately a small axle, that said it will take a LOT of abuse, and its not worth the hassle and mismatched wheel lugs for no real reason.

Rebuild your calipers(its cheap and easy), check the rotors for thickness and buy good pads, if you are worried about your brakes

 

I wonder then if the mid year change was just on the GSL, because all Ive owned nothing but 83's, 3 of them, ranging from build dates of 9/82 all the way to 4/83 (which i got from the original owner) and all had small axles.
Also, are you sure the rear on your car wasn't swapped at some point? I don't doubt you that it had the large axles, just trying to find the truth