Has anyone done a late model rear axle swap?

[turbobuick1]

I have a '72 C20 truck that I'm downgrading to 1/2 ton status, and am looking to see if someone has done a relatively easy (I'm assuming some brackets would need to welded on) rear axle swap, from a newer GM truck.

I have the stock Corporate rear axle with the removable third member with I'm assuming 4.10 gears. I'm looking for a more highway oriented gearset, say 3.42 or so. I could change the gears, but if I can, I would like to swap in a newer, possibly lighter junkyard/used rear axle with gears closer to the 3.42.

Any ideas on this? If it comes down to it, I will look into available rear axle gear sets for my stock axle. But a junkyard/used axle swap would be cheaper and quicker, if it's not terribly involved.

[ChevLoRay]

Is your truck a coil sprung chassis, or does it have leaf springs? I am assuming that you have coils, since you mentioned welding some brackes, etc.

If you have leaf springs, I think it would be easier, although the spring pads on the later axle will probably have to be moved to align with the springs on your truck.

I wish I had the talent to put a coil-spring rear end under my '96 GMC. The ride of my '69 is so much better than my '96.

[turbobuick1]

Originally Posted by ChevLoRay

Is your truck a coil sprung chassis, or does it have leaf springs? I am assuming that you have coils, since you mentioned welding some brackes, etc.

If you have leaf springs, I think it would be easier, although the spring pads on the later axle will probably have to be moved to align with the springs on your truck.

I wish I had the talent to put a coil-spring rear end under my '96 GMC. The ride of my '69 is so much better than my '96.

It is a coil spring truck, I forgot to mention that. I agree, a leaf spring rear axle with close to the same width would be a much easier swap.

But like you I have the coil springs, and wanna stick with it!

[ChevLoRay]

I haven't bothered to look, but I know there are coil-spring swaps for the later trucks. Check Early Classic Enterprises, McGaughey's, CPP and the vendors on-site (Wes at Classic Heartbeat, for instance).

[into69z]

I have a 69 3/4 ton custom camper model that originally came with a 4:10 rear gear. I found a 1986 3/4 ton rearend( corp 14 bolt semi-floater) with a 3:23 gear and swapped that into my 69. I went to CPP for the brackets( they have a kits which provides the axle brackets and brackets for the panhard bar along with a new adjustable panhard bar-$125.00) The rearend cost $100 at pick-a-part. I don't weld, so I had a shop do the work which cost me $780.00

The estimate was $500.00 to remove the old rearend, weld on the brackets and install the "new" rearend-but be warned-the things I did not know were:
the brake lines are different on old(69) vs newer(86), the emergency brake cables were different and had to have later model installed and because the 69 differental was "longer" (front to back), the drive shaft had to be cut and re-balanced.( I had just cut and rebuilt this drive shaft the year before to install the 468 Big block ) So, the $100 dollar "gear swap" cost me $1,000-but it is cool to drive at 70mph and be a less than 3 grand(rpm).

If I had it to do again, I would consider swapping in an overdrive trans or buying a gear vendors unit. Just remember that the old rearends are almost impossible to rebuild because of available parts and no change out gear sets-so that is why I decided to change the rearend and keep the turbo 400. I will be looking to buy a gear vendors unit down the road so I can have more towing capacity and even better rpm at speed.

Forgot-this is a coil spring rearend

[Longhorn Man]

The later model rears are quite wider, you'll want to take measurements and figure if you can use late model wheels with deep back spacing and still fit in the fenderwells.

[profe56]

I did Swap a 94 suburban 3.42, 5 lugs. on my 69 C10
The rear end, I think is an inch wider on each side, but does not look bad.
emergency brake cables are different but you can use the old ones but will need to make a little more big the hole at the back plate I think 5/8. then you have to move back the brackets are on the chassis.
Also I had to change U-join because the yoke are different.
I also need to work on the track bar, if I show you a picture how is now, looks funny that's why Need to buy a sistem like CPP offers.

[montoya22]

im kinda like you man, im doing the same to my 69' a few things ive been looking into is swapping for a 3/4 burben rear end with 3.54 gears, and sill keep the 8 lug look. however swapping to a 5 would be cheaper and more of a selection when it comes to finding rims.
so ive already changed my 69 spindles for 73-78 disk brakes and have a rear end out of the same year about to go in. i actually have a selection. 3.73 and 3.07. not really sure on what one i wanna put in the back yet, so in till then im rolling about with 5 lug in the front and 8 in the rear.
tho to get the best mpg's and keep the total cost of my project down ive been talking to my chevy guy and he told me tht he would build me a 2004r tranny. its simular to a 700 with out less of the factory problems. he had one he built and ran it behind a 502 with juice and said it never gave him any trouble.
so with that in mind this weekend im going to the junk yard and buying a 2004r for $250 and going to have him build it. the 3.73 would most likly be my selection, just because i'll be running down the road at 65-70mph 1800rpm. and still take my truck out on friday and saturday nights to have fun.

[BlazinC5]

I had to do an axle swap on my blazer project too. But I ended up finding a 5 lug 75 axle from a camper special. my blazer is a 71 with coils. It really wasn't hard. worst part was accually cutting the pads off the 71's axle and not destroying them for the 75's axle. It worked out great for me,, and lines and e-brake cables swapped too. Plus with a camper special it had the big brake drums on it. 2.5" vs. 2" wide. It would be easier if you stayed closer to the year of your parts coming out. I couldn't see what advantage there would be with having somthing out of a very new truck unless it contained a special locker or disc brakes.

[MARKDTN]

Originally Posted by montoya22

....
tho to get the best mpg's and keep the total cost of my project down ive been talking to my chevy guy and he told me tht he would build me a 2004r tranny. its simular to a 700 with out less of the factory problems. he had one he built and ran it behind a 502 with juice and said it never gave him any trouble....

Not to hijack the thread, but bear in mind GM never used the 200R4 behind anything bigger than a "mighty" 307 Olds. Never a 350, never a BB. To build a 200R4 that lasts behind turbo Buicks or BBs takes a bit of money. They will not live long in stock form with a lot of power. The 700R4 got a bad rap early on, but is actually a pretty good tranmission IF you adjust the TV cable properly and use a later core.

[nlped]

I put a '90 leaf spring rearend out of a 2wd Suburban (12 Bolt which was a shocker) under my '70 model 1/2 Ton coil spring truck. My truck had the wider of the 2 stock rearends already, so this one was about 3/8" wider than that. My 18x9.5" Boss 338's fit perfectly with this even wider rearend too.

I cut the stock leaf spring pearches off, ordered the trailing arm perches from CPP ($30) and I used the super track bar from CPP so I didn't have to worry about the short stock track bar mount that's on the housing...mine bolts to the right lower trailing arm. Now I already had the McGaughy 13" brake set up on mine, so the parking brake cable swap was a bit confusing at first, but I worked it out. Not including the actual cost of the newer rearend (because I'd already dropped $1K on it with the brake kit, aluminum diff cover, Auburn pro, 3.42 gear set and new bearings & such), I spent right at $140... I even used the O.E. u-joint and didn't have to shorten the driveshaft