1/2 ton 4x4 vs 2wd rear-end
 

The rear-end in my '86 1/2 ton 4x4 (6-lug) has an Eaton posi and Yukon 3.73 gears and around 10k miles on it.
I am wanting to put this in my '87 2wd 1/2 ton (5-lug).

1) Is this as easy as just awapping the axles; 6-lug for 5-lug?
I believe that the spring perches and everything else of consequece are identical for 2wd or 4x4.
If I am incorrect about this, please let me know ASAP!!!


In the event that this swap is not that easy...

2) The '87 was previously a 3/4 ton (8-lug) and according to the SPID sheet in the glove box had 4.10 gears.
With a T400 I could drive comfortably on the freeway at about 65mph, any faster and it started to wind up a bit (I do not have a tach so I don't know exactly).
The 1/2 ton rear in it now came from an '87 1/2 ton swb that had a 4.3 v6 and a 4-speed manual (with the compound low). No posi.
I have only driven the truck on a highway with a 45mph speed limit but it seemed to be rev'ing pretty good at that speed, so much so that I was convinced that it was still in second gear but that was not the case.
The truck (crewcab) jumps off the line from stops and as nice as that feels, the max comfortable driving speed on the freeway of about 55 is not going to work!
Any idea what rear gears the truck with he 4.3 and manual would have came with; it was a Forrest Service truck if that makes a difference?

PS; 8-lug were 235/85(or 245/75?)-16 and the tires now are 275/60-15.

Re: 1/2 ton 4x4 vs 2wd rear-end
 

i have a 4x4 12 bolt rear-end that i'm going to swap with my 12 bolt 6 lug rear-end. everything is the same, just need to swap the 5 lug axles for the 6 lug axles.

Re: 1/2 ton 4x4 vs 2wd rear-end
 

Just as simple as swapping the axles? Good to hear!

Re: 1/2 ton 4x4 vs 2wd rear-end
 

If the rear end your using in the 2wd is still good you could just change your Eaton diff, gears, maybe bearings instead of having to pull the axles from the truck unless I read wrong

Re: 1/2 ton 4x4 vs 2wd rear-end
 

It is absolutely NOT that easy. Installing a ring and pinion set is a very precise and specialized job. It isn't as simple as un-bolt and re-install into another housing. It will howl something fierce and fail very quickly.

Besides, you have to pull the axles to install gears, so you are not saving a thing.

Re: 1/2 ton 4x4 vs 2wd rear-end
 

Didn't think about the fact that it is precise I just happen to have everything to do this but not everyone is so fortunate my bad

Re: 1/2 ton 4x4 vs 2wd rear-end
 

Big flick...

Use the housing from the 4x4 guts and all in the 2wd. Swap axles, get new drums. If you didn't build the rear in the 4x4, make sure of the spline count before you buy axles if you are getting new ones. 88-91 10 bolt axles went to 30 spline instead of 28 in all the earlier 10 bolts.

When it comes to axle parts, it sure is hard to be Randy's. Local, everything in stock, and good people to deal with.

I still wish I would have bought that forest service truck when you had it for sale...

Re: 1/2 ton 4x4 vs 2wd rear-end
 

Big flick...???

The 4x4 rear-end actually came out of an '85 GMC 4x4. Would the '88-91 even fit width-wise in the housing; I thought the NBS trucks had a different width?

I am suprised you haven't picked up that deisel SWB I keep seeing on CL...

Re: 1/2 ton 4x4 vs 2wd rear-end
 

A machine shop could redrill the axles for 5 lug. They can cut a small groove in the stud centerline on a lathe and then make 5 equal marks and drill. If they know what they're doing shouldn't be a big deal.

You can swap the axles if the rearends are the same width and spline count. No need to mess with the gears.

Re: 1/2 ton 4x4 vs 2wd rear-end
 

I was trying to summarize. That's what I meant by big flick, big picture etc...

I meant suburban and blazer when I mentioned 88-91. They are really common in the u-pull-it yards now and the last rear I got came from one of those.

I hadn't seen that diesel, I'll have to take a look....

Re: 1/2 ton 4x4 vs 2wd rear-end
 

I hadn't even thought about '88-91 Bl/urbans, good info to know that they are different!

Here is that diesel swb.
Seems a lot of money from my perspective, but I am not really into the diesels.
I will list the ad here as it only has a few days left:
"Rare hard to find 85 K10 with 6.2 diesel. Truck runs and drives well. 119K New Automatic transmission with overdrive. Over 20 MPG! Truck is not perfect does have a dent in the bed and a little rust in the passenger rocker panel. 360-xxx-xxxx"

Re: 1/2 ton 4x4 vs 2wd rear-end
 

I had a chance to get some stuff done on the trucks this weekend.

I was talking to a friend of mine and he said to make sure that the backing plates were the same diameter.
While doing that I noticed that althought they are roughly the same diameter, they are shaped different.
The 2wd (5-lug) backing plate is "flat" for lack of a better word while the 4x4 (6-lug) backing plate has an offset to it; they are offset to the inside, towards the diff.

The 4x4 brake shoes are about 2-3/4" wide while the 2wd shoes are about 2" wide.
The drums are about the same width difference also AND this appears to be about the some amount as the offset of the backing plates.

I am pretty sure that there are at least two different size rear brake shoes; 2" light duty and 2-3/4" heavy duty.
We are theorizing that the axles are the same width 2wd vs. 4x4, no matter what brakes are there and that I need to order new drums and shoes for the 2-3/4" brakes and everything should be hunky-doory.

Anyone confirm or refute this?

Re: 1/2 ton 4x4 vs 2wd rear-end
 

ask keith seymour

Re: 1/2 ton 4x4 vs 2wd rear-end
 

You guys are right. Both housings are the same width the parts in either housing would fit the other housing.

You can swap axles and drums to make a 2wd into a 4wd and vice versa. The 4 wheel drives all had the big (2 3/4" wide) brakes while the 2 wheel drive stuff could be had with the 2" or 2 3/4" brakes. I've never had a truck with the small brakes, I think they were mostly on the bare bones type trucks.

You can swap the whole backing plate and drums from the 2wd onto the 4wd housing and use all of your original brake parts OR you can use the big brake backing plates from the 4wd and get some new 5 lug heavy duty drums.

If your brakes worked well in the first place, I'd reuse them, then you don't have to mess with the parking brake cables either. They are a pain...

Re: 1/2 ton 4x4 vs 2wd rear-end
 

The 2wd axle was in a bare bones forest service swb, 4.3, 4-speed truck. I don't think they could be had any more bare bones than that!

The brakes shoes were down past the rivets and the drums showed that.
Also, after driving the crew around the block, the wheel cylinder on one side leaked brake fluid badly and it was quite a mess once the drums were pulled off. Smelled pretty good too!

This is in my crew project so I think it would be in my best interest to get the best brakes possible. When we converted the front end to 1/2 ton I bought all new parts for the 1-1/4" rotors.

Re: 1/2 ton 4x4 vs 2wd rear-end
 

I went to Randy's Ring & Pinion at lunch to schedule getting the rear-end done.
They told me that the axles for the 2wd are 1-3/4" different in length (I believe he said narrower?) on each side.
They said that with out having both assemblies in front of them that they couldn't tell me if what I wanted to do was possible.
They kept talking about "brake offset"?

BUT, when I look on RockAuto.com, the axles are listed as:
- 6 lugs; 28 spline; 10 cover bolts; 8.5 ring gear; 31-5/16" length
- 5 lugs; 28 spline; 10 cover bolts; 8.5 ring gear; 31-3/8" length
So that is a 1/16" difference.
They are also the same axles listed whether a 1986 or 1987.

???

Re: 1/2 ton 4x4 vs 2wd rear-end
 

I had always heard you just swap axles and be done.

I have seen guys weld up the holes and have the redrilled or order axles, but I'd swap guts before I did that.

I've done it before without setting anything up and it has never howled or broke, but you really should take the time to set it up right, then there's no chance of it screwing up or giving you problems, you can do it once and know it's done right. Or have someone do it for you. All you really need is a dial indicator and some marking compound.

Re: 1/2 ton 4x4 vs 2wd rear-end
 

OK, so I just about got things wrapped up this weekend but ran in to one last little hitch.

I believe that the e-brake cables were designed for the "flat" backing plates with the 2" brakes. The distance between the "beveled" backing plate and the bracket that the end of the cable attaches to is different enough between the 2" and the 2-3/4" brakes that I can't get the cable to work.

The passenger side has adjustment so I was able to get it done.
But I could not see any adjustment for the driver side; am I missing something like there is an adjustment farther up the frame or something?

Re: 1/2 ton 4x4 vs 2wd rear-end
 

Dang it.
I think I found one difference between the 4x4 and 2wd housing...

My driver side drop shock has been bottoming out and couldn't figure out why.
I bought a DJM shock extender and it came nowhere near mounting to my bracket.
If you look at the pictures, the "flatter" shock mounting bracket that I am holding the shock extender next to, that is the 4x4 housing.
The bracket that hangs farther below the axle (on the red jack-stand), is a 2wd housing.

This wouldn't be an issue if this wasn't a lowerd truck.

Dang it!

Re: 1/2 ton 4x4 vs 2wd rear-end
 

Came up with a solution; using the shock extender as inspiration and having access to SolidWorks, a full sheet-metal/fab shop at my disposal, and with the help of a friend well versed in the art of welding, got this problem solved...

Re: 1/2 ton 4x4 vs 2wd rear-end
 

hello fellow gm lovers I am a newbie to the forum but no stranger to chevy

sorry for adding to the old thread but Kevinr1970 you never posted what you had to do in order to overcome the 1/16" issue I am very interested to find out what you had to do to make it work

was it in the heavy duty drums?

did you file off the 1/16" from the axle ends?

I have an 85' c10 long box 2wd with 2.73 non posi

I was thinking of taking all my 2wd axles backing plates and drums hardware and shoes and put them on 87' 4x4 posi w 3.73's that I got for next to nothing and am just itching to wake my motor up with.

I put a 2' lift on mine plus an add a leaf so i dont think i'll have the shock problems

I could really use any insight from someone who has just gone thru this process 1st hand. I have no doubts i could figure it out with both diff's torn apart but i use my truck for work and the less down time the better

thanks in advance

Re: 1/2 ton 4x4 vs 2wd rear-end
 

I was just thinking that and found this old thread... so the c10 2wd backing plate fit just fine on the other rear end..

Re: 1/2 ton 4x4 vs 2wd rear-end
 

Any chance you're still on here? If so, what are the chances that they could make another set of those?