Allright, I got a rear-end off a member from this board, I swithching from my drum-brake, worn out posi rear-end to a disc/posi rear. But anyways, I pulled my rear-end out and then I called the guy, it turns out he is busy so I can't stop by and pick it up. So I'm gonna go get it in about 2 weeks when it's convenient for both me and him.

Anyways, I was telling my friend, he's saying I NEED to take measurements when I swap rears. What measurments do I take? They're both 7.5" 10 bolt 3rd gen rears, so they'd be the same right? He told me that I still need to take some measurments so when I put the new one in the car doesn't go down the road with the rear-end crooked. How would this matter though, I mean even if I did take measurments and it was off, what can I do about it? Nothing like the LCA's or Panhard bar is adjustable, so I wouldn't be able to really change it anyways. So what should I do, take measurments? And if I do, where do I take them?

One more thing. Since I'm going from drum-disc, what exactly do I need? Should I get all the brake stuff from the junction block back or what? Also, I know I need the proportioning valve too, but where exactly is that in the braking system? I can't get my brake lines to seperate from the junction block either? How should I go about getting them off, I've used plenty of PB Blaster on them and they still won't budge......



-Thanks, Brandon

 

No measurements necessary.

Just nod politely, appear to agree, and go on about your business.

As far as the brake thing, that would depend on what brakes you're putting in. If they're the crappy cast-iron Saginaw calipers, you need the master cyl and the proprtioning valve. If they're the better aluminum PBR calipers, you don't really need to change anything.

The proportioning valve is the thing right under the MC with all those lines going to it.

 

Hmm.... I'm picking it up for $130, and it's just outta an '88 Trans Am with an L98, so is there anyway to tell whether they're aluminum calipers or not? Also, Why would the master cylinder have to be changed, what's wrong/different about the old one? Thanks.

 

Hmmmm.... 88 would be the old cast-iron ones. Bummer. The PBRs started in 89.

The hydraulic needs of the 2 are different. The MC bores are sized differently, so that a given movement of the pedal, moves the correct amount of fluid. I could be wrong but I believe that the Saginaw calipers take ALOT more fluid, such that if you use a drum MC, they'll work even less than they otherwise do (which isn't much to begin with); but I could be wrong about that. The proportioning valve is different for similar reasons. The PBR calipers on the other hand use about the same amount of fluid flow in normal operation as drums do; so they same MC & PV will usually work OK with them. In fact in 91 & 92 the factory part #s were the same for both disc (PBR) and drum brakes.

There's things you can do to make the Saginaws sort of somewhat work sometimes. Rebuild the calipers, and ADD THE GM RECALL KIT; and do the legendary proportioning valve mod, once you get the right PV & MC. Then, use the parking brake EVERY TIME YOU GET OUT OF THE CAR, and twice on Sundays just for good measure; because that's how they adjust. They're not exactly self-adjusting like front discs are.

 

Hmm..... so would this even be a huge improvement over the stcok drums? Is it even worth it? How much more $$$ would you say this is going to cost me over $130? $50 or so? How much is the approximate cost of a disc rear w/posi and PBR calipers?

 

Alot of folks don't like the rear tires sticking out the extra 1.5 inches, but if you wouldn't mind the look, a 4th gen rear can be gotten for not much more, with nice LS1 disc brakes and posi - I got mine for $175 - bolt it in, swap the prop valve, rig the E-brake cables, and your there. You can search on TGO - there are pics of the 4th gen rear "look" with 3rd gen wheels.

 

I've heard it's 2" wider total, is that true, or is it 2" wider total on each side? And if it's 2" wider on each side.... then yeah I mind, that looks like ****.

 

 

Closer to 2 inches each side - but I know mine doesn't stick out that far - Like I said - I remember reading that the LS1's were slightly narrower, but I can't confirm. Unless your getting the better brakes on a 3rd gen rear, I wouldn't think it would be worth it - unless you were getting 373 posi anything, then you could do a brake swap on the 373 rear, whether C5, LS1, LE1, or whatever floats your boat (and fits your wallet).