Front crossmember swap - junkyard searching for 1-1/4" rotor model - 1/2 vs 3/4 ton?

[Chuck78]

I searched the junkyards a bit today, looking for a suitable front crossmember to swap into my 62 GMC panel truck. I wouldn't really mind keeping the torsion bars to keep it simple and have the cool adjustment, but at the same time, it'd be nice to have piece of mind that I could get replacement parts locally fairly easily, or if I was on a road trip. Also, it would make swapping to newer power steering and disc brakes pretty simple if I could just swap out the whole crossmember.

I found three '83-87-89 suburbans today. Measuring the rotors, I saw the 3/4 ton model definitely had 1-1/4" 8 lug rotors (forgot to check the diameter!!!! doh!!). Another was a half ton, rotors were almost 1-3/16" thick (I'm guessing 1-1/4 that's been worn down and turned/machined). Another two actually, now that I remember (might have been a pickup of that era) was definitely 1-1/8" rotors. I was expecting to see something like either 1" or 1-1/4", but the different rotors were much closer in size.

I know that people say on here that the rotors were 1-1/4 73-87, but then I see some people saying they can be found on 80-87 also. Don't forget, Suburbans (and maybe 1 ton trucks?) held over on the chassis changeover until 1991. A 1991 Suburban looks just like an 87/88/89/90.

Now if my choices here are either 1" vs 1-1/4", I would assume that maybe since the burbs are a heavier body all around, that maybe they all have the 1-1/4" rotors, and I was just seeing some really worn or machined rotors in the boneyard? Were there 1-1/8" rotors in that era?


Also, is the crossmember/subframe/suspension the same for this type of swap if I got it from a 3/4 ton? The springs would do me good with the heavy GMC big block V6.

Still looking at a $125 kit that I can use with my current setup to keep the torsion bars and use 73 Calipers and aftermarket 6 lug rotors. I'd almost want to just swap the whole member if I can do it cost effectively.

Lastly, what MC and power booster is an easy swap into these vehicles? I'd prefer to go with the dual diaphragm style booster for performance and space savings as well. I picked up a clutch MC with remote reservoir from an 85 C10 or C20 today, so that solves that problem with the integrated 62 clutch/brake master cylinder. If I use the slave from it, looks to be slightly different diameter from the stock, so I'll most likely need to and fab a mounting bracket for the slave unit.

Thanks,

Chuck in Ohio

[bagged74]

the rotors will be 1" or 1.25" all of the suburbans should have the 1.25" rotor. to my knowledge all 2wd blazers and suburbans had the 1.25" rotor. I cant say for sure on the trucks i guess it just depends on the specific equipment on the truck.

[Chuck78]

That's good to know, then. I had a hunch that was the case, due to the large body and the 5200lb weight of the 'burbs. There were 3+ suburbans there in the yard, but only one C20 2WD pickup, and one 4WD that obviously has no parts that I'm looking for.

What about a 3/4 ton crossmember and a-arms vs. 1/2 ton? Like I said, it'd be nice to get the heaver springs due to the GMC big block weighing about 220lbs more than an all-iron sbc. If other parts were more heavy duty on the 3/4 ton, that might be nice as well, although my 1/2 ton 1989 'burban seems pretty darn well built up front, as is, but I was just curious.

Still up in the air about keeping the torsion bars, and buying the $125 bracket kit to use the early 70's calipers, hoses, and aftermarket rotors. Easy parts availability is definitely a plus with the x-member swap, but the original stuff is fairly unique and it is adjustable ride height is a very cool feature!





Also, I saw a seriously beefy rear sway bar on a suburban, leaf spring rear. I can surely make it bolt up to the coil spring/trailing arm rear end of the 62 with some work, but is this a good thing to use when crossing over from a leaf application donor vehicle to a coil rear?

[bagged74]

I believe the control arms are the same on 3/4 and 1/2 ton. i believe the 3/4 has different ball joints though. i think you could change the ball joints and spindles over to 1/2 ton pretty easily. as far as the crossmember itself it should be the same.