what did i do wrong? 63 c10 axle swap with 71 not working out

[neverwinter]

i really tried to do a ton of research. from what i read the 71 or 72 rear ends from c10s were the best donors due to using coils springs and trailing arms. i assumed that it also meant the axle perches would be in the same spot and that the panhard bar mount would be close. either i made stupid assumptions or somehow my stuff is way off.

i have a stock 63c10 longbed 4-speed floor shift 283 with the original 12 bolt rear. i wanted to get a better gear ratio and 5 lugs so i looked for a new rear axle.

i had a 79 c10 rear axle but it would need the kit from speedway to get the panhard on there and to weld the axle perches. no problem but then i found a 71 c10 near, me so i grabbed that one. so i got everything from the 63 and the 71 apart.

tried to install the 71 rear axle onto the 63 trailing arms and the axle perch pads arent close to the stock locations - meaning i will need to get the stock perches removed and weld in the new ones from speedway anywa. and the panhard bar is way off.

can someone tell me why people recommend using the 71 or 72 rear axle if it takes the same work as making anything else work? just curious as i was told numerous times to try and find a 71 rear as it drops in - when mine clearly doesnt. just trying to sort where i went wrong.

[neverwinter]

ps - wondering if i can try and pinch the trailing arms a bit to narrow the gap and then get the axle perches located with the ubolts?

[fleetsidelarry]

the axle perches should be the same for the '71 and the '63. and, no, I don't think the panhard bar is the same.

the '60-'62 perches are wider apart (by about 4" per side, IIRC) due to the big difference in the frame. does your frame have a couple of inner rails running parallel to the trailing arms?

[neverwinter]

ill check the frame when i get home but i think everything is stock. ugh what a cluster lol

[padresag]

perhaps you are on a 60-62 frame. there is quite a bit of changing bodies going on and this is one of the downfalls if it is the case here. believe that the 71 axle is a little longer , but the perches should line up
ron

[fleetsidelarry]

note the differences between the '60-'62 frames and the '63-'66.

http://67-72chevytrucks.com/vboard/s...43&postcount=5

the '60-'62 was 42 inches wide at the rear, the later frames were 34 inches.

also, if yours is a '62, it should have torsion bars instead of coil springs in the front.

[jchav62]

Originally Posted by padresag

perhaps you are on a 60-62 frame.

This is what I was thinking. Do you have coils up front or torsion bars?

[neverwinter]

i had coils up front also. no torsion bars. i replaced the front crossmember and everything with one from a 79 for disk brakes but the setup that was on the truck was a coil setup. this is getting odd.

[1963c-10]

And the 12bolt wasn't a 62 option. Must be a 63 up frame unless someone already swapped the diff out. Possible the 71 rear isn't a 71.

[neverwinter]

yah the 71 had coils in front and rear also. everything seemed to line up/bolt in as it should unless perhaps someone did swap things out. but even if they did swap rear axles and use the stock trailig arm locations, should the rea axle drop into the 63?

[redneck6]

post pics of frame , axles in ? may be a big help . there should be a D.O.M date stampe in to the axle tubes wanna say drivers side axle tube .

[GMR-PERFORMANCE]

My truck is a 62 with X frame and it never had torsion.. so as we all know most auto makers are great at using up parts or swapping in the new ones if they are short.. My truck was built in may and it was coil up front.. But are not all of the old wider rear ends the 8.2 front load??? I have found that to be a quick check as to what frame it has for width. As well the X frame is not a true 100% c channel frame.. IF your front section was partly boxed then there you have it..

[neverwinter]

ok so i just tried to get some measurements and somehow the stock rear end seems a bit longe than the one from the 71? maybe someone did do a swap into the 71 i really dont know. heres some pics of the 71 rear end on the stock 63 trailing arms. not the gap on the drivers side tailing arm where the u bolt is - i really think the arm is cockeyed a bit too. you cant see from the pics but with the ubolt in the on the drivers side the pass side is off by about an inch (the axlepad is inset 1 inch too far to use the ubolt).

there are pics here and ill try and post them too:
http://neverwintercycles.com/autos-1963-c10.php

[neverwinter]

the next 2 photos are the stock 63 rear axle. and the last 2 are the gap i a seeing with the 71 axle atop the 63 trailing arms. hope this helps. i do have a 79 c10 rear axle that i can also use but that will obv need to have the pads and panhard welded to it.

does this clear anything up?

[padresag]

i would just put a jack between the backing plate and the trailing arm and mate it up. there should be some lateral movement there to move it and put the ubolt in. could just be the spring holding it over.
brake line shouldn't run under the ubolt either
you can measure from centre to centre on your perches to see if the are the same measure if that is not to difficult. that will easily tell you if there is a difference
ron

[chevy_mike]

First off, Get that brake line OUT from UNDER the U-bolt!!!! That is not the correct location and will get pinched off/rub through if you leave it.

Second, I am not sure about '63 but I know '64-'72 coil rear axles have the panhard bar mount cast into the housing and a stud that came out, that the bar bolted to. The "'63" rear end has the early style bracket setup. Two things come to mind, one, someone swapped the rear end at some point in its life. Second, this might be an early build '63 and GM was still using the early style mount until they switched over to the later style. I ran into an early build '68 C10 that had a factory ram style PS system.

As for the later axle not lining up, the springs are likely your issue. When the trailing arms are not connect to the axle but still have the springs mounted, they can pull the arms in directs that don't line up with the axle. I have found removing one end of the spring (frame or arms) allows you to move the arms enough to line up and tighten the u-bolt to the axle. Then connect the springs (without the panhard bar connected). Once connected, use a ratchet strap and pull the axle one way or the other to line up the panhard bar.

Hope that helps.

[fleetsidelarry]

what padresag said. your's is not the problem with the earlier axles, their pads are WAY off. you may need an adjustable panhard. the '71 axle IS 1.5 inches wider, overall (wms to wms), than the '63

and good catch on the brake line, chevy_mike

[Captainfab]

Your '63 did have the correct 12 bolt differential, and your new one does look typical of a '71 truck 12 bolt. The '63 and '64's had the longer panhard bar with the mount on the passenger side axle tube. You can use the '65-'72 panhard bar, but the frame end will need to be bent slightly. An aftermarket adjustable panhard bar wouldn't be a bad idea, but the same bend will be necessary. As for the trailing arms not lining up with the mounting pads, this is typical of when they are unbolted from the differential. Built up stresses from years of use and abuse will cause them to spring out of position. I would use any of the previously mention methods to just pull them back into line. If you want to double check, just measure the spacing of the trailing arm mounts on both differentials. I'll bet they are the same. Of course the overall width of the '71 differential will be 1.5" wider than your original differential.

[LostMy65]

Yes, as Captain suggested;
Check to see if the mounting pads are in the same place for both axles.
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[3757chevy]

Did you ever get this to work?

[Tx Firefighter]

Originally Posted by 3757chevy

Did you ever get this to work?

I doubt the original guy is around much anymore since the thread is so old, but I have personally put a 72 rearend into my 63. Somewhere on here I have a build thread with "Farmtruck" in the title or something like that. There's probably pictures of it in there. The axle itself was a straight bolt in deal. No mods. To overcome the differences in panhard bars I simply used an aftermarket bar since I was lowering the truck anyway.

The original poster just needed to pry his trailing arm a little to line up the ubolt holes. Old trailing arms, tired bushings, etc. They move side to side a modest amount if needed to line everything up. I'd probably have used a ratchet strap over to the frame to nudge it sideways as needed to line it all up. The panhard bar will center everything properly in the end.

[88Stanger]

I agree, simple manipulation of the arm is all that is needed, I used ratchet straps, one on far side frame then to arm, ratchet into place.

Originally Posted by Tx Firefighter

I doubt the original guy is around much anymore since the thread is so old, but I have personally put a 72 rearend into my 63. Somewhere on here I have a build thread with "Farmtruck" in the title or something like that. There's probably pictures of it in there. The axle itself was a straight bolt in deal. No mods. To overcome the differences in panhard bars I simply used an aftermarket bar since I was lowering the truck anyway.

The original poster just needed to pry his trailing arm a little to line up the ubolt holes. Old trailing arms, tired bushings, etc. They move side to side a modest amount if needed to line everything up. I'd probably have used a ratchet strap over to the frame to nudge it sideways as needed to line it all up. The panhard bar will center everything properly in the end.

[3757chevy]

I really just wanted to bring this back to the top as I have a friend who is getting ready to put a '71 C10 housing under his '63 Suburban and wants some info on the swap. I told him he would need 71-72 K10 axle shafts to keep the 6 lug pattern. Thanks for the reply.