I don't have the JK Rubi any more but I rolled into a 2010 Hummer H3T with the adventure package. It is stock 4.56 with 33's. It has a 5 speed manual though. I do have to say it is just about perfect. I get 16-17 mpg 80-90% city driving - like clock work. And that is with all time 4wd.

I wish 1st was a tad lower, but as you see below, the JK has a lower 1st gear. Your OD (6th) is not as tall so you will have slightly higher revs in 6th. I run 2200ish at 65 mph. JK will be 56mph or so.

I think you will find 4.56 a good balance. See the gear ratios and the speed acheived in each gear at 2200 rpms on 33's...

JK tranny ratios of
Gear Ratios 1st 4.46
Gear Ratios 2nd 2.61
Gear Ratios 3rd 1.72
Gear Ratios 4th 1.25
Gear Ratios 5th 1.00
Gear Ratios 6th 0.84

Hummer ratios of
1st 3.75:1
2nd 2.20:1
3rd 1.37:1
4th 1.00:1
5th .73:1

Speed at 2200 in the JK
1st Gear (mph): 11
2nd Gear (mph): 18
3rd Gear (mph): 28
4th Gear (mph): 38
5th Gear (mph): 47
6th Gear (mph): 56

vs Hummer of
1st Gear (mph): 13
2nd Gear (mph): 22
3rd Gear (mph): 35
4th Gear (mph): 47
5th Gear (mph): 65
6th Gear (mph): n/a

RB

 

true but for most jeeps with 33's a 4.56 is a good gear ratio.....decent power gains and decent gas mileage......but to be honest i have never dealt with an auto jeep unless it was a V8 so I retract my statement

 

Wowzers Planman . . . okay I've got to think about this all again.

In general, I've been steadfast on 33s simply because my plan has been to build the Jeep up just a touch beyond stock, perceiving that to be the safest compromise between form and enhanced performance at a reasonable cost. My lift for example is only about 2". My increased tire size would only add an inch. I've put on 1.5" wheel spacers rather than new aftermarket wheels. Instead of one crappy clutch driven LSD, I'd planned on two high quality ones. Etc etc.

So the idea has been to improve form and function without terribly increasing the stress and wear and tear on the vehicle or seriously changing its geometry. If I went to 35s with my current set up, I'd solve my gear dilemma but end up with tire carrier issues and deeply challenging my front axle.

But I do like the Rubi take off idea, and that is something that has quite literally never occured to me. I've got to rethink all of this now.

I have been looking to see if anybody is ditching their TrueTracs in favor of some lockers to see if I can find them used, which would obviously mitigate some of the cost of the original plan. I do think that LSDs would be more useful to me than lockers.

But still, rubi take offs . . .

 

Folks are generally pleased with the stock e-lockers in rubi axles such that they're not being routinely ditched for ARBs or something similar? Perhaps an ignorant question I know, but I've just never investigated this route. I'd think in addition to gussets some new ball joints might be in order too, especially if I was going to end up with 35s . . .

 

Final question then I'll stop bothering you about this: It occurred to me that the type of folks that are pulling off their Rubi 44s to swap in 60s might not have been all that kind to their 44s. What would you look other than obviously bent or broken parts to inspire your confidence a set of used 44s? I'd expect many have been beaten like crazy, even if they look okay in pics after a power washing.

 

10 years later. If you're on here, MTH: Did you ever get 4.56 gears? If so, how were your RPMs at 75mph (or 80) with those gears, tranny and 33's on your 3.8?

About to get 4.56 on my 3.8 w/ manual and 285/70r17s. Getting to Moab or St. George from where I'm at requires going on I-15 where the speed limit is 80mph., which does ok at 80 on flat. But, when the hills come... I get ANGRY and so does my clutch and motor on 3.21s. I'm excited.