63-66 vs 67-87 front cross member differences?????

[64-454ss]

I've read several posts/threads about guys changing the front crossmember when they add disk brakes off a donor truck. I'm curious as to why the extra work? Am I missing something? When I swapped the front A-arms/spindles from an 81, they bolted right on with no issues. Can anyone please clarify if there is an actual difference? It's not a part that wears with age. Is there a difference in track width or ride height??
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[Captainfab]

There's no difference that I know of from '63-'72. The '73-'87 crossmembers have larger LCA U-bolts, which of course can be drilled out on the earlier crossmembers. Then there are some applications where swapping the entire suspension, crossmember and all is necessary. Thiswould be when converting a C20 to a C10, and also when upgrading a '60-'62 truck. When I started doing this conversion in the early '80's, I would leave the entire suspension assembled, and install it that way. It is quick to get the truck back on the ground as a roller, and then worry about what needs replaced later. That is unless of course there is something obviously unsafe that needs attention.

I have also seen a few guys, purchase the later model suspension and completely rebuild it as money and time allow. Then once it is done, swap the complete suspension, with minimal downtime.

[64-454ss]

That does make sense. Thanks for the info! When I bought my parts, everthing was already stripped off for me. Kinda wish I would have known 15 years ago when I did it that I could have just done the whole thing as a roller. I probably wouldn't have had that wrench slip off one of the bolts and hit me in the 2 front teeth..... Ouch!
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[kieth]

We rebuilt the 91 burb front end off the truck, then just slipped it in place on my 66 gmc, also used all the later model steering components so it all worked properly. it does widen the track 3/4" per side......

[64-454ss]

Thanks for the info, Kieth. So, if I were to put a later model sway bar on the front, (finally) I'm taking that the holes in the lower A-arms are not going to line up for the end bushings. Another question would be, do you know if the wider 3/4" per side is in the crossmember or A-arms. Seems like it would have to be in the arms because the upper arm mounts in same place against frame (a constant width on the trucks). If the lower (attached to crossmember) was 3/4 wider per side, I'm thinking that would cause some crazy alignment issues! Now I'm ready to grab a tape measure and head to wrecking yard to compare on trucks with original parts. Haha!!
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[Captainfab]

The later model ('73-'87) front sway bars bolt right up. The C20 camper specials and the C30 have a larger diameter sway bar. IIRC it is 1-3/16" or 1/4".

The increased track width is in either the spindles, the rotors, or both. The CPP modular dropped spindles are supposed to move the wheels back in that 3/4" each side.

[66-PMD-GMC]

Originally Posted by Captainfab

There's no difference that I know of from '63-'72.

Speaking of the 4 bolts that go through the side of the frame into the cross member on 68-72 cross members, I found the top 2 bolts and the bottom rear bolt holes in the same location as the 63-66 units but the front bottom bolt is off and the frame hole needs to be oval-ed out.
On the 73-87 cross members 1 top hole and the bottom forward holes are different.
I also found with 67-87 cross members that the holes that locate the bottom leg of the motor mount frame perch are in different locations depending on year, original motor and 1/2 or 3/4 tom units.
I prefer the 3/4 ton cross members because the upper A-arm locating bolts are beefier but still take the 1/2 ton A-arms. I really cant see any differences in the upper A-arms other than the ball joints that are used and I believe they are all interchangeable.
Speaking of A-arms, the screw in bushings are way easier to deal with than the press in. I can do the screw in type in my driveway.
I have only done about 7 of these conversions so far and probably about 9-10 frame swaps, (67-72 frame under a 63-66) so I am still discovering new things.

[stsalvage]

Originally Posted by 66-PMD-GMC

Speaking of the 4 bolts that go through the side of the frame into the cross member on 68-72 cross members, I found the top 2 bolts and the bottom rear bolt holes in the same location as the 63-66 units but the front bottom bolt is off and the frame hole needs to be oval-ed out.
On the 73-87 cross members 1 top hole and the bottom forward holes are different.
I also found with 67-87 cross members that the holes that locate the bottom leg of the motor mount frame perch are in different locations depending on year, original motor and 1/2 or 3/4 tom units.
I prefer the 3/4 ton cross members because the upper A-arm locating bolts are beefier but still take the 1/2 ton A-arms. I really cant see any differences in the upper A-arms other than the ball joints that are used and I believe they are all interchangeable.
Speaking of A-arms, the screw in bushings are way easier to deal with than the press in. I can do the screw in type in my driveway.
I have only done about 7 of these conversions so far and probably about 9-10 frame swaps, (67-72 frame under a 63-66) so I am still discovering new things.

I have said that until i was blue in the face to all the guys that get the 1973--87 front clips.Me i like the screw in one so much easyer to work with and that last longer

[66-PMD-GMC]

Is that a 63-66 truck in the photo?

[65truckowner]

I just completed the complete swap from an 83 chevy truck . The reason I swapped the whole thing was the one under my truck (65) needed some attention and the one I put under it had a whole lot of new parts already installed. Quick and easy I am also converting to power steering.

[66-PMD-GMC]

Originally Posted by 65truckowner

I just completed the complete swap from an 83 chevy truck . The reason I swapped the whole thing was the one under my truck (65) needed some attention and the one I put under it had a whole lot of new parts already installed. Quick and easy I am also converting to power steering.

Yeah that 63-66 front suspension is weak! unless I changed the U-bolts I ain't driving in it.