DIFF GEARS and axles? (1 Viewer)

[Beach80]

Rig: 93 HDJ81, 37" tires, Gturbo green wheel, pdi intercooler, Manta 3" exhaust, WAT extreme valve body, 3.11 low gears and 10% underdrive in xfer case. Rig is used offroad but 3 to 7 hr highway drives (usually in mountains) are not uncommon to reach fun destinations.

Question: What diff gear ratio would you go with and what brand?

What chromoly axle brand? Or would you stay with stock axles?

I'm looking for input from 1hdt owners on how their diesel performed with diff ratios

 

[tmarx]

4.56 Nitro Gears

 

[AussieHJCruza]

4.10 and 35s seemed fine with a H151, so 4.56 most likely, but given the auto has a taller overdrive, maybe 4.88?

 

[Outono]

I have a similar build, but running 35" tires on stock axles. I've regeared to 4.88. The revs are a little high at highway speeds, but with 37" you'd be pretty comfortable. I have zero trouble going up hills.

 

[Beach80]

Here are the rpm #'s for different gear sets in my rig. The numbers include that I already have a 10% underdrive and low gears. Let me know your thoughts.

 

[mudgudgeon]

4.56 is very close to stock.
4.88 is 10% lower gearing than stock.

If you're intending to use it offroad a lot 4.88s would be an advantage.10% more torque for hills before you need to use low range.

10% more torque for hills on the highway too. But it also means more RPM and engine noise on the highway.

 

[bug616]

I have 1HDT with 37s and 4.88s. I do a lot of off-road and mountain driving. In my opinion 4.88 isn’t quite enough. I’m going to install the 10% under drive as well.

RCV CVs and axles are the way to go. Stock rears are fine unless you’re super aggressive in the rocks or towing.

 

[Beach80]

I have 1HDT with 37s and 4.88s. I do a lot of off-road and mountain driving. In my opinion 4.88 isn’t quite enough. I’m going to install the 10% under drive as well.

RCV CVs and axles are the way to go. Stock rears are fine unless you’re super aggressive in the rocks or towing.

If you haven't already, do the 3.11 low range gears in your xfer case when you do the 10% underdrive. Gives you 3.3 out of low range combined with the underdrive. One of my favorite mods so far.

4.56 is very close to stock.
4.88 is 10% lower gearing than stock.

If you're intending to use it offroad a lot 4.88s would be an advantage.10% more torque for hills before you need to use low range.

10% more torque for hills on the highway too. But it also means more RPM and engine noise on the highway.

I'm still trying to decide......thank you for the input.

 

[mudgudgeon]

If you haven't already, do the 3.11 low range gears in your xfer case when you do the 10% underdrive. Gives you 3.3 out of low range combined with the underdrive. One of my favorite mods so far.

I plan to do this at some point. Will do 4.88 gears and 35s or 37s next time I need tires.
I have a H151 5 speed though. It has a high 1st gear.

I'm still trying to decide......thank you for the input.

My previous cruiser, I changed the gearing by about 10%. Higher gearing.
The drop in torque was quite noticeable. And on the highway the drop in torque meant it had a hard time in 5th gear at times.
The constant shift back to 4th for hills got annoying. The reduction in cruising RPM didn't outweigh the more frequent gear shifts

10% in the opposite direction will help with hills, and will mean you hold high gear or OD longer on hills.