231j vs 231HD

[Kego814]

so my j transfer case is toast and i caught wind of a direct swap of a 231hd. it appears that the bolt pattern between my 99 xj and the 231hd would be the same but my confusion comes with input splines and output yoke sizes.

is this a simple bolt up and go? (im a mechanic with lift access and a box full of tools) do i have to swap yokes? custom axles? i can get axles made if i have to. i just want to know what im getting into. i've done searching and havent found anything helpful.

 

[ehall]

what vehicle is the 231-hd coming from

 

[1-tonxj]

so my j transfer case is toast and i caught wind of a direct swap of a 231hd. it appears that the bolt pattern between my 99 xj and the 231hd would be the same but my confusion comes with input splines and output yoke sizes.

is this a simple bolt up and go? (im a mechanic with lift access and a box full of tools) do i have to swap yokes? custom axles? i can get axles made if i have to. i just want to know what im getting into. i've done searching and havent found anything helpful.

Bolt pattern on 231 hd and probably all 231 ---6---same will bolt up ...trans output ??? needs to be the same as your aw4 23 spline out put or it will not slide on to your trans output shaft ...lol...you can swap this input on the case ,but need to break down the entire case to remove the planet set to swap...now at this point you probably have a 231 from a Dakota and that will most likely only have a 3 planet gear set you would be taking the time to do this just to get the bigger rear 32 spline out put and a larger chain, which you can get 32 spline sye pretty cheap and I bet you don't need a bigger chain than the 1 inch stocker ...I don't and If I don't you...probably... don't .

 

[clean4drxj]

With upgrading the internals it would have me worrying about the case as the next potential weak link.

 

[1-tonxj]

The 231's case gets a bad rap from folks who...have slacked chains...no skid plates covering it , and bad drive shaft bind under droop or worse when compressed hard and the shafts shuve into the case...If the TeraLo Planet gear set did not look like something that comesfrom HarborFreight when sat next to the OE planet set i would probably have one with the big chain and neve look at the Atlas ,but they do look like they should say Pittsburgh Tools on the side .

 

[Kego814]

Okay so from what im gathering a 231j case with a 6 pinion planetary, wider chain and new fork? I should be good? Or do i use a 231hd case and upgrade the planetary? It'd be helpful if there were a spread sheet that identified various key parts between the common jeep cases. Such as the 241having a 6 pinion planetary and the 231hd having wider everything and the 231 internal specs laid out.

 

[ehall]

The middle digit is the case strength, so NP-231 or NP-233 they are the same case strength. You need to an NP-24x to get the stronger shell.

Some of the GM NP231-C had 4-pinion planetary, some of the GMs came with a 241 with the stronger case and the 6-pinion planetary and the bigger chain too I think (old GM 241 is fairly different from JK 241 and completely different from the 241-OR). Some of the GMs had 32-spline main shaft (an NP-233C is a 231 with a motorized shifter and a few upgrades), but there's no SYE or HnT for them that I know of. I don't know which Dodge came with what but the info is out there.

 

[Kego814]

What do the 1st and last digits denote?

 

[ehall]

1st digit is the number of speeds, 231 and 242 both have high and low speeds, so they are "2"

3rd digit is just the model number

 

[Kego814]

Got it thanks bud i think im going to stick with a 231 and beef it up