Thinking about axle swaps...

[Ochre]

Ok, so I've got a '71 K5 Blazer with no rear axle that I recently purchased...first order of business is going to be getting a rear axle and tires under it to facilitate moving into the machine shed...it's too damn cold to work outside!

I'm not a serious 4x4 guy (though I have friends that are), however I frequently get called upon to pull people out of ditches and occasionally help in recovering friends who have gotten stuck at the local mudhole...my driveway is rather steep and so if its icey I need a 4x4 in order to actually get out onto the roads occasionally, so a 4x4 truck is a necessity.

I do, however, tow a lot, and have a custom 20' flatbed trailer and will soon be getting a towing dolley so I can stop borrowing my friend's to move smaller vehicles when the need arises. I have a converted truck bed trailer to haul tools in, and I also occasionally tow a duck or ski boat for friends. When finished, my blazer will definitely be equipped with proper wiring for any sort of trailer, a brake controller, leaf load leveler and quite possibly towing airbags.

I realize that a K5 isn't the best vehicular option for pulling a trailer, and if I had the space and money I'd invest in a late '80's K or V2500/3500 crewcab, however, I don't have either and for the time being I want the best I can reasonably get as far as handling and controllability both with and without a trailer.

Since the rear axle is already gone, I'm at a good point for changing if I want to, and I'm considering my options. I want your opinions on doing the following:

1) Replacing missing rear with stock 6-lug 12-bolt. Local guy has a posi 6-lug from a 69-72 blazer for $150
Pros: Easy, nothing to change, bolt-in, posi
Cons: 6 lugs (can't interchange with most used trailer)
Unknowns: Nada

2) Replacing missing rear with 8-lug 14 bolt FF from 73+ 3/4 ton. Different local guy has a front and rear pair in the same ratio as my blazer's front for $100 (both)
Pros: $50 cheaper for axle, get both axles (can sell original front), 8 lugs, front will bolt right in, don't have to change front right away.
Cons: Will need to move spring perches and possibly shock mounts for rear
Unknowns: How far in/out will the tire spacing change?

3) Replacing missing rear with 8-lug 14BFF from 88-98 3/4 ton. Local junkyard has a couple for sale, varying prices ~100-200 (rear only)
Pros: 8 lugs, will move tires out farther than the 73+ rear
Cons: will definitely need to move perches & shock mounts, front tires might not be as far out as the rears, not enough money/time to go IRS in front
Unknowns: How would the wider rear effect handling? Towing?

Right now, #3 seems like a pretty far out option, but its one I'm considering anyway. I'd really like to see before/after pics of either K5's or pickups that have had the #2 and #3 swaps if anyone has them. I'm leaning towards #2, but concerned about changing the tire spacing - if anything I'd like to go outwards a little bit so the tires aren't so tucked into the wheel wells. #1 would be basically replacing stock, and the 6-lug rims I currently have (could sell in a heartbeat) won't interchange with any of the trailers I have.

Ideas? Concerns? Suggestions? I'm open to change before I make up my mind and buy whichever rear is actually going under the truck.

Also, assuming #2 or 3, is it reasonably easy to move spring perches and reuse the old ones, or would it necessitate buying new spring perches to weld-on? I have confidence in my welding ability and equipment (220A stick welder), but haven't moved spring perches before. If I do need to buy new spring perches, where should I get them from?

[b454rat]

I would go with the pair, front and rear. It's not that big a deal to relocate spring pads. Find out what the gears are in the front, and if you find a 1 ton 73-87, it will bolt in, maybe change the shock mounts. The 1 tons have the same spring pad width as 72 and older trucks. I wouldn't go with the 88-up stuff, the rear is fine, but why go thru all that when you could probly get one to bolt in. And, I never measured them, but buddy mine told me that the 88 and older ones are actually WIDER than the 88-up. I thought the opposite cause of the offset that GM uses in that style. You could also use a Dana 60 rear out of a HD 3/4 ton. I have one in my 62 burban, bolted it in, didn't do nada. They use the same gears as GM, so finding a match won't be too hard.

[Ochre]

Originally Posted by b454rat

I would go with the pair, front and rear. It's not that big a deal to relocate spring pads. Find out what the gears are in the front, and if you find a 1 ton 73-87, it will bolt in, maybe change the shock mounts. The 1 tons have the same spring pad width as 72 and older trucks.

Unfortunately I'm betting I'll be hard pressed to find a 1-ton axle in 3.73 ratio, I'd go for higher if the blazer wasn't so light and I wasn't too poor to afford something with an OD gear.

I wouldn't go with the 88-up stuff, the rear is fine, but why go thru all that when you could probly get one to bolt in. And, I never measured them, but buddy mine told me that the 88 and older ones are actually WIDER than the 88-up. I thought the opposite cause of the offset that GM uses in that style.

I recently helped a friend swap an $86 gov-lock rear from Upullrparts (www.upullrparts.com) from a '87 Sub into his '97 K1500 (his rear end ate the pinion bearing and was destroyed). I'm fairly certain it's not as wide, as with the same rims the fronts jut out about 1-2" more than the rear, with the old rear they were the same spacing.

You could also use a Dana 60 rear out of a HD 3/4 ton. I have one in my 62 burban, bolted it in, didn't do nada. They use the same gears as GM, so finding a match won't be too hard. I'm actually taking out the 60 rear and gonna sell it, in case your interested.

Well, NY is a bit far from MN, even if your price was good shipping would still kill me. What years HD 3/4 ton? I know the 67-72's got the Eaton Axles, don't know too much about 73+ GM trucks.

[1969 GMC]

Not all 67-72's got the Eatons. My GMC came factory with a D60 rear with 4.10 gears.

That being said, go for the pair. That is a smokin deal, even if you do not use them you can resell and make a few hundred. my 2 cents

[2wdBlazer]

I would go with the 73+ FF. I have one in my Blazer. Your stock rear would be naturally not as wide in the rear. The Corpaorate FF will make your front and rear the same width. I am very satisfied with mine.

[Coleman]

My $.02 worth. I just replaced my old eaton rear (68 K20) with a 14 bolt FF. I found one at my local salvage that appeared to be only an inch off of my current setup. I finally got to this project last week and the new 14 bolt was an exact match, I didn't have to do much other than swap some cables and move one shock mount. Literally a direct bolt on. No drive shaft or spring perch mods. I don't think this is typical but the rear end I used was from an 81 C20.

good luck!

[1967k30]

[QUOTE=Ochre]Unfortunately I'm betting I'll be hard pressed to find a 1-ton axle in 3.73 ratio, I'd go for higher if the blazer wasn't so light and I wasn't too poor to afford something with an OD gear.

I have a set of 1ton's with 3.54's.

[Ochre]

Originally Posted by 1967k30

I have a set of 1ton's with 3.54's.

Nebraska is a ways away...wonder what motor/transmission combo a truck that big with a ratio that small would have gotten?