I tried the search function and it was a nightmare so I'm just going to ask outright

Are there any significant issues with running 37s on the Rubicon's D44 axles? Does anything need to be upgraded for it to be strong enough to turn them with proper gearing? What would be the appropriate gears? New axle shafts?

I'm trying to decide whether to get the 2 door or the unlimited and I want to run 37s, would this be too large of a tire for the 2 door? I'm coming from the XJ world so please bear with me on these noob questions.

Thanks

- Kirk

 

i ran 37's on my rubicon D44 and had no problems - well, except for breaking my factory locker twice. i am no running a sahara D44 with arb in it and have had no problems with it. i am running superior chromo shaft though and would definitely recommend getting a set if you plan on going this route. as far as gearing goes, i am running 5.13's with mine and it works well but 5.38's would give you better power. randys ring & pinion has 5.38's now and i know that david at northridge4x4 carries them.

 

I have an XJ now with 4.56s and its super low for those, with the 5 speed. Would 5.38s really be needed with a 6 speed? Not doubting you, just surprised is all. Also, they'll fit in the pumpkins on D44s? I know my D30 front on the XJ cant handle anything bigger than 4.56s with the ARB.

I've also heard that there is no need to buy a new speedometer gear to calibrate the speedometer, is that true? I have had issues with the XJ off and on since replacing the gear in that one.

Thanks!

 

You can recalibrate the speedo with the Hypertech Max Energy programmer or other programmers. Hypertech also makes a less expensive variant that just calibrates the speedo. You should also be able to use other electric speedo recalibration devices such as The Little Yellow Box, though the programmersare easier.

 

Since I'm planning on moving from 35's to 37's I'm upgrading my rear axle shafts to Superior CM's and the front to AlloyUSA with CTM U-Joints. If you go to CTM's website and follow the links to web write ups and publication you can read about people pushing D44's pretty hard with horsepower and larger tires.

You'll also want to weld on ORE's "C" gussets.

 

but, what size tires are you running on your x, 33's maybe? if you're gonna run 37's, 5.13's will essentially return your performance back to stock. also, on the 44, you can now fit up to a 5.38.

there are no more speedometer gears and haven't been since 2003. you will need to get a calibrator and set your computer.

 

With a 6speed I've heard that 4.88s would work but are better suited for 35s. If it were me I'd go to 5.13s at the very least.

Gotta love drive by wire!

 

Awesome info, thanks everyone!

I am running 33X12.50s on my XJ with the 4.56 gears.

Red - What all would the Hypertech Max Energy programmer tune besides the speedo that would warrant the $$?

Looks like I may need to save up a bit more than I thought before this build up

 

I don't see why you need 4.88s for 35s. With a Stick, you can choose the gear so you don't have the same issue as an auto. I have 35 with 4.10's and have no problems. If you want, you can add 4.88 if you move to 37s as it will help with 6th gear.

Personally, I will go to 4:56s if I step up to 37s.

 

It will allow you to correct for gears/tires, run a specific program for the fuel you use, and reset your fan switch. It can also read diagonistc codes and reset the check engine light. There are a bunch of threads on hear about it, just do a search. I personally have mixed opinions about whether it is worth the money or not. The tune that you get out of it isn't going to provide more low end power, which is where we need it. If you are looking just to get your speedo recalibrated, there are cheaper ways.

And yes, this whole modification thing is an endless cycle that ends up costing more than expected.