Manual transmission choices

[brucecooner]

On 2/17/2024 at 5:33 PM, 89 MJ said:

A Rubicon case may also have an electronic speedometer sensor. I'm not sure if you can put a conventional speedometer gear in or not. Many people run stock 231Js offroad. The biggest difference in capability will be gears and a limited slip in the rear. That said, if the Rubi t-case is a good price, it may be worth buying anyways. 

 

I don't plan on doing any rock crawling, mostly just bumpy rough trails. 

A super low crawl would be nice but without any lift (yet), I can't go anywhere extreme anyway.

Everything I've read indicates the 231 is a medium duty case plenty suitable for bumpy wheeling.

This Jeep already has a Dana 44 in the rear with limited slip, which I hope makes a pretty good setup with the 231.

 

The seller said the case is from a TJ, I don't know if their speed sensors were geared or electronic.

 

 

On 2/17/2024 at 7:33 PM, ghetdjc320 said:

Are you talking TJ rubicon or JK rubicon? 

He said it is from a TJ.

 

 

On 2/17/2024 at 7:59 PM, Eagle_SX4 said:

If you do get an AX15 drilled for a wrangler you will need to redrill for the Cherokee/Comanche transfer case clocking. The transfer case will not bolt up to it unless you cut or severely bash the floor. The problem then becomes you might need to make new seat brackets or find different seats.

 

My truck had an AX15 in it when I bought it. But someone put the wrong fluid in and it ate the synchros. I managed to buy a second one for cheap and rebuilt it. Only after I swapped the freshly rebuilt one in did I realize it had come out of a wrangler. The transfer case would not line up with the holes drilled in the output flange. I ended up drilling the new holes in the transmission with it under the truck. It was not fun.

 

Aw man, not much is fun to do under the truck.

I've seen a video where a guy had to drill his AX for a Cherokee, but he was able to level it on a bench. 

 

When you said it requires body mods, did you mean only if the clocking is wrong?  Or is the Rubicon case just too darn big even with the correct angle?

 

I believe the product page at Novak said you can request an XJ clocking on a new transmission and they will do it for you, which is my best hope.

Apparently you can get a jig that goes over the spline and uses the existing (Wrangler) hole for registration, with another hole off by 10(?) degrees to tell you where to drill for the XJ.

 

 

 

The guy selling the Rubicon transfer case said something that shocked me though.

He said the AX swap would require new driveshafts.

 

But I've read plenty that says even though AX is about 1/4 inch longer, this will be taken up by the slip yoke on the back of the 231 (unless you want to go with SYE and driveshaft mods).

 

Can anyone speak to that? 

Am I really looking at new driveshafts here? 

Because if so I might as well set up for a future lift.

 

 

[ghetdjc320]

The tail housing is not hard to drill at all (with a jig and out of the truck) but a clocking ring will work just fine too. Plenty of spline engagement still on the tcase. That way you can clock it wherever it needs to be. The 241 is slightly bigger and it does use an electronic VSS with no provision for a mechanical speedo on the output. The 242 is even larger and will fit under an MJ with some very slight mods. 241OR also has a different driveshaft coupler but can be simply adapted. 

The length difference of the tranny doesn’t necessitate a driveshaft change for most installs. 

 

https://www.ebay.com/itm/303597948710

 

[Eagle_SX4]

5 hours ago, brucecooner said:

Aw man, not much is fun to do under the truck.

I've seen a video where a guy had to drill his AX for a Cherokee, but he was able to level it on a bench. 

 

When you said it requires body mods, did you mean only if the clocking is wrong?  Or is the Rubicon case just too darn big even with the correct angle?

Yes it would have been easier to drill it on the work bench. By the time I realized the clocking was different the transmission was already in the truck and I didn't want to take it out again.

 

5 hours ago, ghetdjc320 said:

The 242 is even larger and will fit under an MJ with some very slight mods.

 

 

I have a 242 in my truck. It fit nicely once I redrilled the transmission for the proper clocking angle. If the 242 is larger than the 241 you should not have to modify the body at all as long as the transfer case is clocked correctly.

[pizzaman09]

Having recently changed the output shaft seal on my factory installed AX-15 with NP231 T-case, I'd estimate that there is an extra inch of length the driveshaft could move into the t case at the slip yoke.  So a quarter to half an inch could work with your stock shaft.

 

If not, just take your driveshaft to a drive shaft shop and have it shortened.  I had that done for another truck and it was easy and affordable.  Same goes with if you need a different end installed, it's quite easy work for someone that is setup to do it.

[brucecooner]

I got a recommendation from the local speed shop for a transmission shop today, and they pointed me to a guy I've already been recommended to by someone else, so I gave him a call.

 

Unfortunately he doesn't do installs, he's just a builder, but he's done lots of builds for the AX swap and for what I'm doing he highly recommended keeping the 231.

 

Which is fine. 

I haven't heard anyone disparage the 231, I'm going to baby this thing no matter where I go, without a lift I can't take it anywhere extreme anyway, and I'll save some dollars for that future lift (or maybe someday I'll just get a TJ for wheeling *GASP*).

 

On the upside, he can provide a rebuilt AX without a core for a reasonable price (cheaper than the online suppliers I've seen) and he's not far down the road so no shipping.

 

He'll rebuild a 231 with the new input for installing at the same time, and this is where it gets interesting.

My plan has been to source another 231 to attach to the AX, because I can't disable my Jeep for however long this takes.

But this guy said I have to be very particular about the 231 I get. 

It has to be clocked for an XJ (or I guess I get an adapter ring), but it has to have the same speedo, linkage, and actuator mechanisms.

I did plan on updating the linkage though.

He said to get the assembly number off of mine and go by that.

I looked at the tag on mine and found 89530 04301

 

So I've got some kind of plan, but now I'm wondering where and how I get the exact case I need.

 

ebay has a lot of listings, but they are literally ALL for Wranglers.

I guess I'm down to checking the for sale forums, and snooping for Cherokees at the u-pull-it.

 

 

[ghetdjc320]

Couple of things to clear up, the 231J’s all have the same clocking. The difference is in the transmission tailhousing not the tcase. As for the Speedo provision, pretty much any jeep np231 will have the Speedo provision you need. There are different speed senders over the years but they all fit the same Speedo hole in the case. Same goes for linkage. Your variable is the type of tail housing as some have an accordion style rubber and some gave a fixed metal tail one with seal for the slip yoke and also the spline count. You’ll need a 23 spline input which are super common anyway. No need to hunt down a specific serial number case.

[brucecooner]

15 hours ago, ghetdjc320 said:

Couple of things to clear up, the 231J’s all have the same clocking. The difference is in the transmission tailhousing not the tcase. As for the Speedo provision, pretty much any jeep np231 will have the Speedo provision you need. There are different speed senders over the years but they all fit the same Speedo hole in the case. Same goes for linkage. Your variable is the type of tail housing as some have an accordion style rubber and some gave a fixed metal tail one with seal for the slip yoke and also the spline count. You’ll need a 23 spline input which are super common anyway. No need to hunt down a specific serial number case.

 

I'm on the hunt.  You'd think a city the size of Phoenix would have a few old 231's for sale but no luck yet.

ebay's always a possibility I guess.

 

I do have some rando questions though.

 

I'm looking at this one:

https://www.ebay.com/itm/126324479362?itmmeta=01HQ7HGHQ1HFEF6TKCKNGDHRP4&hash=item1d69869582:g:rr8AAOSwi9xlxoGr&itmprp=enc%3AAQAIAAAA0HzP%2FqzUPm%2BfBXCWCxdA60XO9cOCCWNmijd1Q4XppxL04%2B%2BuI1dO2WvPQTEUr2oZ8167EZpJYP%2BG%2FeZKyCrmXPheq3A3chpRxdDph%2F82pICCMPGsJTckunponoxiGf%2FVI07581fFZdjT22t5j0GDOWD1XaXmc8ArL0l3ZPF940zVT6eV5jfEFPHHCvNPRLvjYnGg0Pf4N53VhLWTSP4RjVBh0gJcx890W77EeoteGGujG1FbcITjO8xUZn9TxBa2pZDisPDfZKPTZ%2BWCs061JJI%3D|tkp%3ABk9SR9CbwvG5Yw

 

The listing says "Automatic" in the title.

I haven't seen any indications that the manual/standard transmissions led to any differences in the TC.

I assume all 231's will have the exact same bolt pattern, and I don't even have to think about manual versus standard sourced cases.

 

I've seen "short input" on some listings.

I assume that's something on the input side, is there anything I should be aware of there?

 

My output side is definitely NOT the accordion style, which I see on a bunch of listings for later tc's.

I took a picture of my tail shaft today.  Part of me wants to say that tail housing is longer than the one in the ebay listing, but I really don't think

that is possible.  Or did tail shafts vary from year to year?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

But yeah, thinking that may be my next tcase...

 

 

 

[Eagle_SX4]

According to Novak's website that one should be a 21 spline input shaft which is not what you want you will want something with 23 splines.

 

Here is Novak's write up on NP231 input shafts.

 

https://www.novak-adapt.com/knowledge/np-nvg-input-gears/

[cruiser54]

Check with Christian. 

[pizzaman09]

If you need any evidence to support how sturdy the NP231 is, Matt's off road recovery recently stated that the transfer case in their Cherokee (Banana) was the original NP231.  That Jeep has a 4.6L stroker and has been beat on harder than most.  

[brucecooner]

3 hours ago, pizzaman09 said:

If you need any evidence to support how sturdy the NP231 is, Matt's off road recovery recently stated that the transfer case in their Cherokee (Banana) was the original NP231.  That Jeep has a 4.6L stroker and has been beat on harder than most.  

 

I read this just today on the Novak site...

 

"The standard duty OEM 231 transfer cases are capable of transferring from 1600 to 1900 ft. lbs of torque (as claimed by NVG - actual experience puts this number quite a bit higher)."

 

I don't think my motor is going to put out anywhere near those numbers anytime soon.

 

Speaking of Novak, I called them today to inquire about a rebuilt 231, and he said the input side should be the short option for an AX, but that it was pretty forgiving, the output shaft is long enough to work with a range of cases.

 

And they can get me a completely, and I mean completely, refurbished 231 for not much more than I'm out getting it from the builder, considering my options here...

[pizzaman09]

11 hours ago, brucecooner said:

 

I read this just today on the Novak site...

 

"The standard duty OEM 231 transfer cases are capable of transferring from 1600 to 1900 ft. lbs of torque (as claimed by NVG - actual experience puts this number quite a bit higher)."

 

I don't think my motor is going to put out anywhere near those numbers anytime soon.

 

Speaking of Novak, I called them today to inquire about a rebuilt 231, and he said the input side should be the short option for an AX, but that it was pretty forgiving, the output shaft is long enough to work with a range of cases.

 

And they can get me a completely, and I mean completely, refurbished 231 for not much more than I'm out getting it from the builder, considering my options here...

I assume that torque figure is at the input shaft of the transfer case.  First gear on the AX-15 is 3.38 so you need to multiply your engine torque by 3.38 to get how much torque is going into the transfer case.  There can also be a little more torque if you rev up and drop the clutch as the inertia of the flywheel also stores energy that becomes torque.  Regardless, it is likely that for most any one with a 4.0 derived engine in their truck, there is not going to be an issue with strength of the NP231.

 

More likely if you manage to send that much torque through your transfer case, your tires will break traction first, which limits torque getting to the ground.  

[cruiser54]

They're strong enough for built Chevy 350s. No worries.