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Gears/Axles shafts

trustyrusty77

trustyrusty77

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Hopefully this is a quick one. I have a 77 K5 with a 350/350/203. Dana 44 front and 12 bolt rear. stock gears ( 3.73s???) I have 35" LTB's on there now with a 6 inch lift. im adding a couple more inches and want to go to 38" tires. what gear ratio do you all recommend for the front and rear?

secondly, will I need to upgrade my axle shafts to something like chromoly shafts? I have a ton of experience in offroading and this sort of stuff but the knowledge stops at 35" tires and 4.56 gears. I've never ventured past that realm and don't want to start breaking axles. down here in Houston there isn't a lot of rocks but I try and stay away from mud. its a trail rig mostly but one day MOAB is in the works..

appreciate everyones feedback!
 
You sir have opened a big can of worms!

If your dead set on keeping it 6 lug, I'd say go with a 6 lug s.f 14 bolt from a 88-98 obs truck.

Also you can 8 lug swap the front axle and toss a 14 bolt FF in the back.

A truck 12 bolt isn't worth spending the coin on.

You can go the 1 ton route like I did, never had any issues with my 10 bolt front. Just this site got the best of me and one thing lead to another :haha:
 
For 38s id say 5.13 gears. Id agree on the 12b rear being a waste for the money you will put into it. 14ff is what id do over the 14sf if I did it again. 14sf is expensive to buy new parts for.
 
As mentioned skip 12b. Get a 14 bolt full float for the rear and try to find a dana 60 for the front. Carry spares if you wheel a D44 on rocks. If your going to be driving your rig to the trail on 38s you have to make the judgement of comrpimise for gear ratio.

I just went through the Rubicon with 40s and 4.10s...it wasnt too bad but obviously needs to be lower. Im going to 5.38s but i trailer to the trail.

4.56s are pretty easy to find used and cheap but a huge advantage over 4.10.

If it were me and i was driving to the trail it would be 4.88 so your not screaming down the freeway. 5.13s would work great but are you ok with sitting at 3000 rpm at 65?

http://ratfactor.com/gear-ratio-tire-rpm-calculator#scroll-to-results
 
I tend to agree. 12 bolt is not worth it if you gonna run 38s. Look for some 3/4 ton axles.

I had to do 38s on my 73 with 4.10s crawling sucked but I love that combo.

I suggest looking for a matched set of 8 lug axles. If you wanna stay 6 lug look for a sf 14 bolt. That said I have seen a locked 12 bolt hold up to 38s pretty well. Course he had over a grand in his axle when it was all said and done and would still break every now and again .

He eventually sold his 12 bolt and bought a 14 bolt ff
 
well looks like its time to start saving. there is a gentleman here in town that every now and then acquires axles, rebuilds them, and sells them with whatever gear ratio you want

would I need any upgraded axle shafts in the 14bolt and 60?

thanks for all your replies, I was afraid of them though!
 
Not on 38s. Most guys never upgrade 14 bolt shafts. Dana 60s are pretty reliable up to 40s with a front locker.
 
Depending on how you use it, you could possibly get away with a GM 10 bolt or Dana 44. A 3/4 ton swap is a lot cheaper.

Martin
 
I would highly recommend going at least 3/4 ton which means a 14FF rear and 8-lug D44 or 10-bolt front (or swap over the current axle). These axles can be had pretty cheap. The big expense when going 1-ton is the D60 front axle.

If you go 14FF you never have to worry about swapping to another axle again, they are relatively cheap and easy to work on. Swapping the front over to 8-lug is cheap and easy also with the advantage being you are already set up for 8-lug if you need to go to a D60 down the road.

The other thing I always tell people is that having a beefy rear axle is a big plus. On the trail you can break the front axle and usually the worst that happens is you shift into 2wd, maybe need a few pulls to get back to the road, and then drive home. Breaking a front axleshaft also usually isn't that big of a deal to fix on a trail if you go that route. On the other hand if you break the rear 12-bolt (same pertains to a 10-bolt) it often completely disables the vehicle. A broken axleshaft is a big PITA. You can limp off the trail if you can keep the tire from falling off and maybe limp down the road at 5 mph but that is it. A lot of diff failures will also cause it to lock up and make the truck undriveable. With the front axle you just unlock the hubs and go.
 
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