[chrisflock]

I am trying to replace the rear axle in my 87 chevy 1/2 ton pickup. It's toast.

Anyway, my dad has a pair of work vans that are destined for the junkyard, and I was thinking of taking the rear end out of one of those.

Both vans had posi rear ends, but my dad knows the rear in the 91 van was replaced once, almost certainly with an open diff (this is confirmed by a burn-out test in a wet parking lot)

The other van should still have the original posi rear, although it appears that it doesn't lock up anymore.

I figured it will probably be a lot easier (cheaper) to rebuild the posi rear in this than to buy an entire posi rear for my truck. My real question is what type of posi unit might this be? I know that it is a 10 bolt rear axle, but haven't had a chance to yank it nad see if the numbers are still readable and whatnot...

Anyway, the van is an 87 3/4 ton with a TBI 305. Anyone know offhand what type of posi would be used?

Chris

[M&M CUSTOM]

It could very well possibly be the not very desireable Gov-Loc which requires some amount of traction loss to allow the counterweight to swing out to match the teeth and lock up both sides.

It doesn't always work, and with a good amount of abuse they can engage with enough force to basically "explode" some of the internal parts, thus the reason they were given the nickname "exploding locker".

I have pics on here somewhere to be able to determine which type of traction enhancing carrier you might have.

[jimfulco]

Here's a pic of a Gov-Loc

[Bumpstick]

Uh the van rearend is around 4" wider than the pickup rearend... Not that it would`nt work but would look kinda funny...?


Also Gov-loc`s suck... I destroyed 2 just as described above until I bit the bullit and bought and Eaton posi unit with Richmond gears and have never looked back...

[Crosley]

yes they blow up..... mine pitched parts through the sheet metal cover

Originally Posted by M&M CUSTOM

It could very well possibly be the not very desireable Gov-Loc which requires some amount of traction loss to allow the counterweight to swing out to match the teeth and lock up both sides.

It doesn't always work, and with a good amount of abuse they can engage with enough force to basically "explode" some of the internal parts, thus the reason they were given the nickname "exploding locker".

I have pics on here somewhere to be able to determine which type of traction enhancing carrier you might have.

[chrisflock]

What about the spring mounts? Are they at a different width?

I also see that the 91 chevy vans list as 31 13/16 axles, so maybe I should try to use that rearend (even though it isn't posi)...

I guess that I can get a cheap lock up...

Anyone know if the powertrax lock-right is any good? I am on a very small budget.

Chris

[M&M CUSTOM]

Your interest in the Powertrax unit is probably going to increase.
These are true lockers with 90º tooth to tooth engagement unless there is sufficient traction to disengage one side or the other to allow somewhat normal differential action, but with enough foot into the go pedal you can keep the teeth engaged.

They are a true gearhead do it yourself upgrade.

[chrisflock]

So, perhaps if I gank the rear axle from one of the later vans, pop a powertrax locker in it, throw it into my truck...

I'd be able to get around a little better in the winter, powerslide when I want to, but still go around corners without clicking or tire chirp?

If those powertrax are all they claim to be, they'd be great for just about anything!


Chris

[M&M CUSTOM]

Originally Posted by chrisflock

I'd be able to get around a little better in the winter, powerslide when I want to, but still go around corners without clicking or tire chirp?
Chris

You WILL have both tire chirp AND clicking, and some axles make this more evident than others.

From a little curiousity search, I came up with your truck most likely having the 14-bolt 10.5 inch ring gear axle, and possibly having the 14-bolt 9.5 inch ring gear axle.

The 1991 ¾-ton van you mention should have the 10-bolt 8.5 inch ring gear axle.

These are interchangeable but some careful measurements must be made to ensure you aren't getting into more work than you want. Here are some things you should do or consider.
Measure the axle from flange-to-flange.
Measure from the middle of both leaf spring perches.
Measure from axle centerline to middle of axle universal joint (difficult).
If those numbers all compare relatively close, you can move to the next step.
You will most likely have different size universal joints, they make a joint that will adapt the differences into one joint.
You will most likely have smaller axle tubes on the van axle, requiring smaller inside diameter U-bolts and the plates that go with them (you already have them on the van axle).
You will most likely find that your driveshaft will need to be extended as there will be a smaller axle swapped into the truck.

The differences in width can be made up with a swap of rims with proper backspacing to more match what you already have now.

Let us know what you find out.

[Bumpstick]

I dont think a 1987 1/2ton pickup will have a 14 bolt rearend...? More likely it will be a 10 bolt 8.5 just like the van...? Possibly a 12 bolt but doubt it...

Also with that in consideration the rearend in question has metal in the bearings from the minor catastrophy... So a complete rebuild would be a better option... The van rearends are wider and since they both have issues I would leave them to the junk masters... The idea of the Powertrax setup is also a crutch (also it will not fit your gov-loc carrier)... Take it from someone that has used the more expensive unit its for pulling boats out of the water not any kind of racing or even much playing around (they kick out when both wheels spin above a certain RPM and make god awful sounds)... Do it right and simply look here and with a little work you have something that you can trust...


BTW the better Powertrax unit cost over $400 by itself so for a little extra its all new and right...

[chrisflock]

My truck has a 10 bolt rear...

And it's trashed. I don't think it's rebuildable, I think the tubes are bent. Not to mention the shock mounts are both bent, and its so rusty that it probably won't be long before the rust holes go all the way through.

I'm going to try checking with the junkyard and see if they'd have a whole rearend they'd give me in trade for the vans or something...but I don't think I'll be able to survive the coming winter without posi, at least not it i snows like last year.

I'm starting to think maybe I should ditch the ol girl and get something else. I would like to get a jeep wrangler, or maybe a 4 wheel drive pickup...

Chris

[M&M CUSTOM]

Originally Posted by chrisflock

I am trying to replace the rear axle in my 87 chevy 1/2 ton pickup. It's toast. . . .

Anyway, the van is an 87 3/4 ton with a TBI 305. Anyone know offhand what type of posi would be used?

Chris

OOPS!! I mis-read which one was where for the ½ ton and the ¾ ton, all three vehicles should have the corporate 8.5 inch axle. I mis-read which one of the 87's had the ¾-ton rating.

Both of the 87 axles have 28 spline axleshafts, and the 1991 has the 30 spline shafts. The spider gears and axleshafts will interchange as a whole.

I have never had the opportunity to work on any full size GM vans so I cannot say what the length difference is.

[chrisflock]

We popped the diff cover on the 87, and it's an open rearend. I kind of suspected this, as I was pretty sure that this was the truck the rear end fell off (literally!) a couple of years ago, and was replaced with a non-posi. This was also confirmed by the new spring mounts to the frame, and some visible scratching to the underside of the frame where it hit the ground, the new gas tank, and the loose bumper with all the crome worn off the bottom and half of the bolt/nut on the bottom of the hitch ball cround off (the truck was going a good 30 when the rear end ripped off, so the truck skidded for a ways...

Anyway, it was dark and we were getting tired, not to mention I was doped up from having my wisdom teeth ganked out ('dry socket' is not fun. A more appropriate name for this condition, since it has more to do with the socket getting saliva in it, would be 'Dear god why does it hurt so much! What did I do to deserve this! Why!") so we didn't try taking the cover off on the other van. Also, since that van runs and drives, we didn't want to dump the fluid (as we didn't have any to put back in).

Also, I noticed the fluid that glooped out of the rear end was green. I mean really green. Is that normal? I've never seen green fluid for a diff...


Chris