I've been going back and forth about what gears to put in my military K5. I've got a D60 for the front and 14ff for the rear. I'll be running 37" tires and have a TH400 trans. I'll use it for driving to the trail as well so I do need some highway ability. What do you think? 4.10? 4.56? It has 3.73's in it right now?
CK5
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Please help! What gears for my 6.2?
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4.10's if 37's are as big as you're going. I have a M1008 with the 4.56 gears and the same drivetrain and even with the 38's it's a bit low geared.
Thanks. I've got a set of 4.10's for the front. I can use those and just try to find a set for the rear. I have a set of 4.56's for the front as well but I'll wait to put those on until I move up to 42's? Meanwhile, I'll be looking for a set of 4.10's for my 14ff. Oh, and a detroit for it too. Know anyone selling these off hand? I'll start searching now.
thedrip
1/2 ton status
same drivetrain with 42's, and 4.56's seem to work out alright. Could use more gear in town, less on the highway, so its a happy medium
MaxPF
1/2 ton status
I'd leave it 3.73's since you lack OD. If you want better trail gearing I'd consider a doubler. It probably won't cost you much more than buying and installing a set of gears, but you will be able to keep a better gear for street & highway and have much better crawl gears for the trail.
I would keep the 3.73's also. That will give you a decent cruising rpm on the freeway. Going to 4.10's would be a complete waist of time and money IMHO as you likely wouldn't be able to tell the difference either on the road or on the trail.
There is a guy in our club that just built a CUCV and did a 3/4 ton swap with 3.73's and 36's, overall he's pretty happy with it (he drives it almost daily, and to and from the trails).
There is a guy in our club that just built a CUCV and did a 3/4 ton swap with 3.73's and 36's, overall he's pretty happy with it (he drives it almost daily, and to and from the trails).
Yeah stick with the 3.73 and if you feel on the trail the low range doesn't give you enough, you can get a doubler for just a bit more than the gear swap, best of both worlds.
I didn't need deeper gears, the deisel low end torque worked fine for that.
I ran 2.73s with 35" boggers -- It was brutal, but actually did just fine in low range off-road 
I could go almost 55 mph in low range with that gearing...
I stepped up to 4.56 with the same 35" boggers, and found I was typically starting off / wheeling in 3rd and 4th gear while in low range. On the highway I was at perfect a perfect cruising RPM in 5th gear at 70 mph. Without overdrive, I think that 4.10s would have been a bit better for the 35s. With your 37s, I betcha your engine would be just fine at 70 mph with 4.56 gears.
I could go almost 55 mph in low range with that gearing...I stepped up to 4.56 with the same 35" boggers, and found I was typically starting off / wheeling in 3rd and 4th gear while in low range. On the highway I was at perfect a perfect cruising RPM in 5th gear at 70 mph. Without overdrive, I think that 4.10s would have been a bit better for the 35s. With your 37s, I betcha your engine would be just fine at 70 mph with 4.56 gears.
