Trans Am disc axles

[Bonnewagon]

I was told that the axles used in the '79-'81 Trans Am disc brake rear were different than the same year drum brake rears. Yes? No? I ask because I have some disc brake parts that I could either use on another leaf spring rear or a G-body rear. If the axles are the same it is a no-brainer swap and I can build another F-body disc rear. If not, then I was figuring to drill the G-body axle for the four bolt rotor brackets like they do for the four bolt bearing retainer kits. The two bottom bolts should line up and then mount the rotor brackets after drilling the top two holes. Since the G-body drum axles locate the drum almost exactly like the F-body I figured they would interchange. I am relying in GM cheapness here thinking they would not make different axles, just adapt the rotor brackets to fit. That way the disc parts would swap over.

 

[MY6.2SS]

I was told that the axles used in the '79-'81 Trans Am disc brake rear were different than the same year drum brake rears. Yes? No? I ask because I have some disc brake parts that I could either use on another leaf spring rear or a G-body rear. If the axles are the same it is a no-brainer swap and I can build another F-body disc rear. If not, then I was figuring to drill the G-body axle for the four bolt rotor brackets like they do for the four bolt bearing retainer kits. The two bottom bolts should line up and then mount the rotor brackets after drilling the top two holes. Since the G-body drum axles locate the drum almost exactly like the F-body I figured they would interchange. I am relying in GM cheapness here thinking they would not make different axles, just adapt the rotor brackets to fit. That way the disc parts would swap over.

I have put together a couple disc brake rears on my 75 Trans Am and 78 Trans Am using the factory 79 and up stuff. The only difference I could ever find is, on the true disc brake axles the center hub was a little taller so it could stick out to catch the center bore of the wheel. If you use non disc brake axles you will see that it is just about flush with the disc brake rotor. That has been what I have found.

 

[spidereyes455]

Mark, the Hollander book says they interchange by replacing the wheel studs. I'm guessing that the disc ones are a smidge longer due to the extra thickness of the rotor as opposed to the drum.

 

[Bonnewagon]

they interchange by replacing the wheel studs

Jim you are the MAN!! That is what I needed to know. Thanks for posting the Hollander pix. I can use that. I didn't think cheapola GM would make two different axles but they did. Good thing a stud change will work. MY6.2SS I can see where that hub height would be a problem with a hub centric wheel. But a lug centric wheel like a snowflake would not even notice.

 

[Bonnewagon]

I had my wheels off the Bonnewagon today to change to my summer rubber. I noticed how deep the register is on the hub. Plenty of space for a disc rotor. But then I noticed that the shocks are not staggered like on the TA. Then I read about Cadillac, Buick, and Oldsmobile using these TA brakes on Sevilles, etc. Some had non-staggered shocks and they used two of one side to get around that? I can't see it- the bleeder would end up upside down.

 

[carnutjw]

There was a Seville at the salvage yard when I went last week on a recon trip(minimal tools). The wheels were on it, but I reached behind and it did have disc brakes. Is there any demand or current use for these if I could grab them pretty cheap?

 

[L92 OLDS]

There was a Seville at the salvage yard when I went last week on a recon trip(minimal tools). The wheels were on it, but I reached behind and it did have disc brakes. Is there any demand or current use for these if I could grab them pretty cheap?

Last time I checked you can still buy those parts new. That’s what I used on my rear end so I could clear the 15” SSIII 442 rally’s. Aside from the E brake set up those calipers are the same as the front calipers on a G body.

 

[Bonnewagon]

The e/brake cables are key. But I only saw re-built clipers for sale and those were going for $50 with a $50 core charge. Worse, there is no guarantee you will get the parking brake levers that are bolted to the caliper, nor the cable brackets and big return spring. I would most certainly grab them, as well as the backing plates/mounts. That means opening the rear end covr to release the axles. But those plates are probably the most hardest to find and going for BIG bucks.

 

[Texas82GP]

We have the WS6 rear disks on my brother's 78 Z28. When we started restoring his car back in 2006, it had an open drum brake 2.41 rear in it that he and dad had put in back in the late 80's. They wanted to replace a wheel bearing in the stock rear but the lock pin broke and they didn't know what to do about it. Their answer was to replace the rear but they didn't know enough to realize they were changing the ratio. They thought all V8 Camaros came with 3.42 gears, when only the Z28's did (at least in the late 2nd gen models).

We initially found a Z28, drum brake 3.42 open rear, hanging on a rack in a junk yard, which we bought. My brother wanted the WS6 discs so later, we ended up buying a WS6 3.08 posi rear on eBay from out of state. We had the guy strip the axles, caliper brackets, calipers and all the brake hardware and ship all that to us. We let him keep the housing and the 3.08 posi because of cost of shipping. I had him send the axles as a "just because."

We put all the WS6 brake parts on the 3.42 drum brake rear end. It was a good thing we had that guy out of state send the WS6 axles. One of the axles in the drum brake 3.42 was bent. I guess it either slapped a curb or it happened in the junk yard. We swapped in one of the disc brake axles and went with it. I don't remember any difference between the disk brake and drum brake axles. Unless I'm mistaken, the car has one disc brake axle and one drum brake axle. I'm not aware of any difference.

 

[Texas82GP]

There was a Seville at the salvage yard when I went last week on a recon trip(minimal tools). The wheels were on it, but I reached behind and it did have disc brakes. Is there any demand or current use for these if I could grab them pretty cheap?

The Seville rotors will not fit the F-Body axles. You would have to turn down the O.D. of the axle flange so the rotors will fit. We bought a Seville rear for my brother's car hoping to adapt the rear discs to it but we abandoned that effort to find the correct F-Body (Pontiac) parts.

The levers, brackets and springs don't come with the rebuilt calipers. I would imagine they are hard to find separately.