1987 gmc axle swap ??

[jesdude7789]

Hey guys,

I am looking to swap the rear axle on my 87 gmc truck because it is a 2.73 ratio. Crappy I know, and it's my daily driver. I have been living with it for 6 years now and I'm thinking that it's time to get a better ratio in it. I found this axle on craigs and it's from a 1991 g20 chevy van that is a 3.42 ratio and I'm wondering if it is a direct bolt-in swap? Can anyone help me out? I tried finding an axle interchange list somewhere but haven't found anything yet. I'm not going to modify my suspension to make something work either.

thanks for any info

[Keith Seymore]

I'm not exactly sure - hopefully some other guys will chime in - but it should be close.

Keep in mind a "G20" is really the same as a "C10" with the 5 hole/5" bolt circle. G vans didn't get the 8 lug setup until the G30 series.

The only thing that might be different would be the positioning of the spring perches. If you jumped on this one and they weren't right it would still be a (relatively) easy fix.

K

[Katrina/10]

It won't fit, van axles are wider than trucks.

[RandyP]

I'm fairly certain it is not a direct swap and fear the width is even different.

Have you tried looking on car-part.com for a local salvage with the rear end you want? I see several 3.42 rear ends that appear to be local to you. Remember, when buying stuff from these salvages, cash is king and they will negotiate usually.

[Tx Firefighter]

Look for 87-91 Suburbans. A ton of them had 3.42 ratios.

[jesdude7789]

Originally Posted by RandyP

I'm fairly certain it is not a direct swap and fear the width is even different.

Have you tried looking on car-part.com for a local salvage with the rear end you want? I see several 3.42 rear ends that appear to be local to you. Remember, when buying stuff from these salvages, cash is king and they will negotiate usually.

thanks a lot. that will help for sure. I didn't know about that site.


What do you think is a reasonable price?

[nekkidhillbilly]

you can use the gears in your axle.

[jesdude7789]

Originally Posted by nekkidhillbilly

you can use the gears in your axle.

what are you talking about?

[nekkidhillbilly]

if your truck is a 8.5 rear. you can take the gears out of the 91 8.5 and put them in your axle in your truck.

[jesdude7789]

Originally Posted by nekkidhillbilly

if your truck is a 8.5 rear. you can take the gears out of the 91 8.5 and put them in your axle in your truck.

I can't be doing that. I don't have the special tools to rebuild an axle and this is my only vehicle that's drivable right now and it's my daily driver. I have to get a whole axle so I can swap it out on the weekend without any possibility of problems.

[RandyP]

Complete axle swap is easy peasy stuff that any old do it yourselfer can accomplish. Swapping gears though, different story, different time zones and different planets usually.

I sell rear axle housing assemblies for $150 - $175 when I have them. So getting one from a licensed salvage yard I would guess $200. As I said though, ask about a "cash and carry" price. Hell maybe you'll at least get tax knocked off or something.

Another positive from buying at a salvage yard, you normally get a 30 day warranty. That gives you a few days to get the part installed and put a few miles on it to make sure it does not have issues. Whereas if you bought from a CL person, once you exchange the money for the part, it's all over.

[nekkidhillbilly]

find somebody who can swap for you. shouldnt take more than a hour or 2. used axle your going to deal with bad bearings and all that, have to replumb your brakes. me id have a the gears swapped with a posi out of another 8.5. replace all the seals bearing and needle bearings while in there. you gotta think a used axle from 91 is going to have a whole bunch of miles and age on it and if a needle bearing goes you got to pull it apart anyhow. just my .02.

[jesdude7789]

Originally Posted by RandyP

Complete axle swap is easy peasy stuff that any old do it yourselfer can accomplish. Swapping gears though, different story, different time zones and different planets usually.

I sell rear axle housing assemblies for $150 - $175 when I have them. So getting one from a licensed salvage yard I would guess $200. As I said though, ask about a "cash and carry" price. Hell maybe you'll at least get tax knocked off or something.

Another positive from buying at a salvage yard, you normally get a 30 day warranty. That gives you a few days to get the part installed and put a few miles on it to make sure it does not have issues. Whereas if you bought from a CL person, once you exchange the money for the part, it's all over.

I did one years ago on my old 89 1/2 ton I used to have until my brother needed it. The stock 3.08 blew out on it one day and my dad got me a used 3.42 axle somehow or another and I swapped it out on a saturday. That gear combined with the holley tbi I had on it made it a good hauler for sure. gas mileage was in the toilet though haha. I am keeping the stock tbi on my 87 so I should be okay.

Originally Posted by nekkidhillbilly

find somebody who can swap for you. shouldnt take more than a hour or 2. used axle your going to deal with bad bearings and all that, have to replumb your brakes. me id have a the gears swapped with a posi out of another 8.5. replace all the seals bearing and needle bearings while in there. you gotta think a used axle from 91 is going to have a whole bunch of miles and age on it and if a needle bearing goes you got to pull it apart anyhow. just my .02.

I wish I knew guys like that but I don't. Any local shop won't do anything but a full rebuild for around $1000 so that's out of the question. I need to get more gearhead friends haha

[Houston Ben]

Hey, another square in my town! I was looking at that exact van a while ago thinking the same thing!! lol

[nekkidhillbilly]

Originally Posted by jesdude7789

I did one years ago on my old 89 1/2 ton I used to have until my brother needed it. The stock 3.08 blew out on it one day and my dad got me a used 3.42 axle somehow or another and I swapped it out on a saturday. That gear combined with the holley tbi I had on it made it a good hauler for sure. gas mileage was in the toilet though haha. I am keeping the stock tbi on my 87 so I should be okay.



I wish I knew guys like that but I don't. Any local shop won't do anything but a full rebuild for around $1000 so that's out of the question. I need to get more gearhead friends haha

yeah i know some guys that can do it for like 200 or so plus parts. i wonder if you would best to buy the tools and do it yourself.

[Keith Seymore]

Originally Posted by Katrina/10

It won't fit, van axles are wider than trucks.

Dang. Sorry bout that.

Didn't mean to lead the OP astray.

K

[kape]

Hello, I swapped the g20 axle on my c10.
G20 axle is 1.968 inch wider on both sides than c10 8.5" rear and. Measured to bearing to bearing.
What i did , narrowed g20 rear end to 5 cm (1.968 inch) on both side. And then i used the old drive shaft. (28 splines.) and cut off all leafspring and shocks supports and relocated them like a original c10. works fine.

[andrewmp6]

If the used rear end is in good shape its cheaper to swap then rebuild what hes got with different gears.