Regear or not?

[cburgess72]

Regear or not? I've been researching, and want to ask some advice. I have been working on my my m725 for years; stock motor with civy 2 bbl car runs great, stock transmission, stock t-case with driveshaft mod. These all in great shape. Humvee wheels made to fit stock hub, ps they look great, Trail Worthy Fab. So i like what i have, will prObably swap for a np205 later. I am only cruising the streets, would like to get on the highway and not get ran over. My question is, swapping the front and rear gears to on my stock axles to 4.56, will I be happy or sad with the ride and milage for the $1000 it costs to regear? I'm interested to hear if any of you with similar setups are glad you made the change.

[randyscycle]

I did 4.56's in my truck and I wouldn't go back.

I do have a Chevy Big Block and a TH400 with 38" Michelins. I can now drive up to 65 no problem and the transfer case doesn't heat up nearly as much with the lower driveshaft RPM. Off-road, I haven't noticed any significant difference.

I am not sure where you'd end up with stock tires and driveline, but it would still be a major improvement if you plan on doing any real road time. You won't regret doing it.

[Kozmo]

I'm glad you asked that. I was pondering exactly the same thing this morning after having read some stuff on the Novak adaptor site yesterday concerning engine swaps.

Is there a thread available which gives a run-through regarding what it takes to do this kind of change-over? Any info on where that $ 1000 figure came from?

Since I have "Noob" permanently tattooed on my forehead, any info would be helpful.

[randyscycle]

There isn't any one thread about re-gearing that I've seen, simply because there is a lot to understand when it comes to setting up a ring gear and pinion. Backlash, pinion depth, gear patterns, and other factors are all things covered in detail for the M-series in the TM's and that is the place to start.

To do a 4.56 re-gear will cost you more than $1,000 in parts if you go new, just for the gears and bearings, then you need a different carrier up front, seals, gaskets, etc.

[Barrman]

To continue as if I was finishing what Randy wrote:

Which is why so often this discussion turns into. "What do I need to put in CUCV axles?" You get stronger shafts, bigger u-joints, 4 wheel disc brakes, 4.56 gears, open knuckles, common 8 lug wheels a locker for sure in the rear and if it is from a M1028, a locker in the front too.

Most people would prefer to cut, weld, grind, pick up huge parts that are several hundred pounds, look for months, drive hundreds of miles and spend more money to get the CUCV axles than attempt to put in new gears. Axle gears and automatic transmissions are still considered black magic by a lot of people and therefore, just aren't attempted.

[kwai]

Not to nitpick, but the M1028 front axle differential is a limited slip and not a locker.

Now back to the original discussion.

[Barrman]

Correct. The front axle on the truck for Sermis has a locker and I forget it has been changed. Sorry.

[cburgess72]

http://www.bjsoffroad.com/prod-957.htm
Kit available. Anybody that has done the swap with this kit please chim in on installation. Also what other rebuilds, or maintence jobs should be addressed while the axles are pulled apart? I am going to get some paid help, which adds to $1000 or so in parts.
If I were starting my whole project over I would buy new cucv axles, but I'm to bought in now to even think about it.
Oh, and the kit looks complete, any other parts needed to complete this project?
Thanks in advance.

Side note- I have fresh paint and wheels on my m725, I'm a lawyer in Ft. Worth, TX, and I've parked that bad boy right in front of the Court House, too fun. Truck is down, losing to much oil out the rear main, can't wait to get her back on the road.

[Mikel]

Unless you are worried about originality, going with newer axles gives you FAR more bang for the buck than messing with the stock ones. Open knuckles, disk brakes, usable gearing, larger shafts, parts availability... Here in CT you can get a set of 1-ton axles for $600 if you look.

[randyscycle]

That kit looks pretty good. It has the shims, seals and bearings pictured. Now, just out of curiosity, are the ring gear thicknesses changed? The M715 D70 rear is different than a common D70 and has a thicker ring gear because the offset is different, and the front 60 has a carrier break at anything below 4.56, so I'd ask before I pulled the trigger on the kit just to be sure.

Its surprising to me that someone had gears manufactured for the military axles and offers them as a set. They must have figured there was enough demand.