Axle swaps m-715 to J-3000

[New in'69]

Hello. Has anyone ever heard of someone swapping in a set of M-715 axles into a J-3000? I have a '69 J-truck, and wanted the heavier axles and running gear associated with the 5/4 ton trucks. Plus, if I get a trailer, I want all the wheels the same size. Should I try to just swap the front fenders et al., onto the M-715, and use it's frame or will the axles be sufficient (with the appropriate spring hanger mods?) on my '69? Any help would be appreciated.

[randyscycle]

I'd suggest using something more modern in your J3000. The M715 axles are geared as 5.87:1 stock and I think the only thing available anymore are 4.88:1 gears and those are getting scarce.

Brake shoes are only avialable from military parts sources, and drum brakes seem like a step backward if you're doing an axle swap anyway.

Then there is the wheel bolt pattern. Only M715 wheels, or custome built wheels fit the stock bolt pattern.

Strength-wise, you're looking at axles that are around the same strength as modern Dana 44's.

[Ronner]

Well, to be fair, the rear D70 is a pretty stout unit. But other than that Randy is right on point. And since the stock wheels are the kind where you have to run an innertube they are a PITA too.
The spring pack is super stout and you could maybe put them on your J3000. But since yours is already a 1ton it isn't worth the effort.

[New in'69]

Ok, thanks, I think this rig ('69) had heavy duty leaf packs on it from it's former life, (unless 8 leaves in the rear and 7 leaves is normal) (2nd owner). It has a few custom mods done since the original owner (I'm 3rd) ordered a bunch of cool stuff from the factory to make a purpose-built rig he could push his way through the woods with, (and he owned a welding shop in the 60's).
I've actually talked the wife into making a road trip to Alaska one day, and will need to have a trailer with all the spares, plus our stuff, and should I need to climb over something in the road, or ford a stream or something, I was wantingto use something 'old and reliable' I've been planning and plotting for two years and can't seem to figure out which way to go with it.
Are you talking something like mid 80's Dodge/Chevy 1-ton axles, and all the mods required? I figured with the same axle/ spring perch widths and all that, that it might go easier.

[New in'69]

If I found a M-715 in a field, (I'm still working on a guy who has two) would they have the 5.88's if it's still stock?

[brute4c]

Stock axle ratio is 5.87 ratio...so if its unchanged from the actory, that is the only gear they put in these...

[New in'69]

Thanks again.

[Ronner]

Especially on a incredibly LOOOOONG drive to Alaska you don't want the 715 axles. The 5.87:1 gearing is cool if you want to push a building down or climb rocks - just not Hwy friendly. And they aren't much better than modern 1/2ton running gear plus as they have said - getting parts is murder
The normal axle swap involves the Chevy military vehicles from the 1980's - the CUCV. Same weight rating of 5/4ton, but much stronger, has disk brakes, normal chebby 8 bolt wheel pattern, and you can get parts at any store out there. They also come with a Detroit locker in the rear and a more Hwy friendly 4.56:1 gear ratio. Super easy to do a spring over in the front and a shackle flip in the rear so you can go with bigger tires if you want. I have done this swap but kept it spring under as the 38.5" XL's I have are probably the biggest I'll ever need. Plus it puts the seat just the right height - well, if you are 6'4" that is
Do you know what axles are under that J3000 already? As a 1ton I'd think that they would be pretty stout already. Be a whole lot cheaper & easier to put a locker in the rear & a posi in the front of the axles already under there if they are up to the task.
Good luck!

[New in'69]

BBM715,
They are supposed to be Dana 44's, closed-knuckle types, with 4 drums. I'm ok with the drums, but I think the CUCV's would be ok too. I'm still researching to find a resonable compromise.
I don't need to get tires over 35, I would think, but that's because I've mainly been a trail rider up to now, with a little cross-country every now and then. There are some places in Co. b/w Idaho Springs and Georgetown that I've wanted to revisit, and I'd need the toughest setup I could feel confident with. There are some places around here (in Arkansas anyway) that are hairy too.
I thought of running some J-20 axles, but they are pretty scarce around here. Besides everything I've read about the turning radius, I'd think if you ever went up (and especially down) a real-mountain fire road series of switchbacks, you could sympathize. I've literally seen places you would drop hundreds of feet before you hit ANYthing, and then roll/tumble forever. So. I guess that's another argument in favor of the upgraded brake setup. Thanks for all your help.

[Ronner]

lol
Then I'd definitely go for the CUCV axles - or chebby 1 ton axles from that era - they should all be about the same. D60 up front with disk brakes and a 14 bolt out back with drums (easy conversion to disks). The things I like about the CUCV axles are the 4.56 r&p and the Detroit locker already in the rear. On my truck right now I have 35x12.5x16 Goodyear MTR's and they are the bomb! Quiet on the road, great on snow & sand, pretty good in the mud, and I hear that they rock on rocks! (sorry for the pun)
This is a good site to use for calculating what r&p/tranny you would want to use with your set up: http://www.4lo.com/calc/gearratio.htm
Civilian axles have the 4.10 ratio a lot of the time and are usually cheaper - but if you decide that the 4.56 (or bigger) ratio is more to your liking the CUCV axles become cheaper considering the cost of 2 new r&P plus the carriers - and you get the Detroit too.
Modern version of the old saying - Research twice and buy once - saves you a ton of cash & headaches in the long run.

Ron