Decisions on how to proceed on 87 GMC

[MTCK]

I believe 12 bolts stopped being made after 1982 or so. That is likely a 10-bolt you found. I would be suprised if it bolted in. I would try to find a rear end from a 73-87 truck. You might think about regearing if all yours needs is a brake job. In my experience hunting around the 2.73's, 3.08's and 3.42's are much more common than the 3.73's or 4.10's...

[Jonboy]

The earlier 4x4 trucks were pretty common with 3.73's. The 2wd and 4wd axleshafts directly swap on a 12 bolt, so that may give you a couple things to look for.

If it is pulling your trailer just fine with 3.08 gears, anything lower has got to help. You could probably swap to 3.73 gears in your existing rear and see quite an improvement. Also, running a lot taller tire (like the 31x10.50) will kill a lot of your gear as well.

[nlped]

The 88-98 rearend isn't a direct bolt in. I did this in my '87. It isn't terribly difficult, just time consuming and requires a welder, and right angle grinder or torch/plasma cutter to do.

The spring perches have to be cut off the newer rearend and moved slightly as do the shock mounts. The advantage to this swap is a slightly beefier axle package (30 spline vs. 28 spline) and larger drum brakes and of course, the many different final drive ratios.

[Tech_Ed88]

Originally Posted by Jonboy

The earlier 4x4 trucks were pretty common with 3.73's. The 2wd and 4wd axleshafts directly swap on a 12 bolt, so that may give you a couple things to look for.

If it is pulling your trailer just fine with 3.08 gears, anything lower has got to help. You could probably swap to 3.73 gears in your existing rear and see quite an improvement. Also, running a lot taller tire (like the 31x10.50) will kill a lot of your gear as well.

Yes, The 4x4 axles seem to be easier to find and a reasonable price too.
They have a different bolt pattern for the wheels though right?

I think my best choice is too have the local tranny shop re gear my axle.

3.73's with the 255/70 R15

4.10 with 255/ 70 R 15 or 31 x 10.5

So, there goes my money I was worrying about burning a hole in my pocket.

[Tech_Ed88]

Hmm,
Well, I found two of the correct axles for 200.00 each

one is a 3.73 from an autosalvage yard.

The other is a 4.10 from an 82 shortbed that was a mild sport truck which also happens to have some american racing 5 spoke wheels and 295 rr and 255 tires too.
I'm going to go take a look and see about it.

[nlped]

Cool, good luck!

[Tech_Ed88]

Thanks.....

The guy with the 4.10's didn't reply after I sent him an email....

but another guy that builds them did. He recommended going with a rebuild instead of buying one from the salvage yard.
That seems to be the best idea if you have the money to do it.

The guy that rebuilds them recommended a 4.10 with a locking diff. since I have the overdrive.
I thought the locker was a bit much but I understand that because it is a 2wd you don't want to get stuck on gravel or soft grass.

Don't these trucks have a limited slip posi anyway?

I haven't got stuck yet though, and I've always parked it in my yard ( on a gravel pad) and drove up through the yard without any problems.

[nlped]

No, they don't have a limited slip typically. When I put the '96 rear under my '87, I put an Eaton Limited Slip in the new set up. It has made a world of difference when I pull the boat out on a wet boat slip. The weight of the trailer makes a world of difference when it comes to pulling

[Tech_Ed88]

Well, I just got off the phone with Bob.
He's the guy that said he could build me a rearend with 4.10 gears and limited slip.
Drop it off on a sunday and have it back that night.

Listen to this price..... I had to call him back to make sure it was both parts and labor.

550.00 out the door. re-geared to 4.10 with posi trac

A deal that I can't pass up.

I think I'll go with either the BF goodrich 31 X 10.5 LT tire or the BF goodrich 255/70 R 15T/A
both very nice tires...

and I'm sticking with the stock ralley wheels too. just going to repaint them and polish the chrome.

[BIG10]

Originally Posted by snc4life

nothing looks better than 255/70/15 bf goodrich radial t/a's on a stock height ralley wheel truck

I completely agree, but I would recommend an LT tire for this application. You can get a LT235/75/15 in several brands/styles with white letters that will still look sharp. Snag that hard cover for $200 if its worth it and have it painted to match your truck. Your 350 shouldn't have trouble with that load. My uncle bought my truck in 1979 and towed a large travel trailer for many years with the stock 350. Add a tranny cooler and temp gauge too. I know you're only going 20 miles, but sounds like you're tackling some mountains. You'll want to keep an eye on those temps. Figure out your brake issue. Otherwise, keep it out of OD, take it easy and enjoy.

[BIG10]

550.00 is a good price. I'm glad you're sticking with the ralley's too. I hope you take some pics of the trailer hooked up and share.

[Tech_Ed88]

How about any of these...

http://www.explorerforum.com/forums/...ad.php?t=82290

[BIG10]

I've only seen BFG Land Terrain's at Wal-Mart and don't know anything about them. The Liberator is also a Wal-Mart tire made by Uniroyal. My dad put some on a Jeep Wagoneer a few years ago and they didn't hold up very long. The BFG Long Trail Tour is a good highway tire, but I don't know if they make an LT. The Michelin LTX is a great tire also. I've been getting good tire prices at Sears lately. You might check out what they have to offer. I know they carry BFG (my personal preference).