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1989 Jeep Cherokee 1 ton swap

There's a year split if I recall at 95 between the gear pitch or whatever

Good to know it's a 23 spline. Maybe it's just a coincidence, the serial number on my two 23 splines start with a 94 and 95 and that's what year I thought they were from.
 
It’s a luck of the draw kind of thing. Since the transfer case was a 242 I was more inclined to believe it was 23 spline, and NO WAY was I buying another 21 spline. I considered putting my 21 spline input into the 242, but I don’t know who would want THAT combination. Especially from a stranger on the internet with no warranty. Maybe I should take one apart for ‘fits and shiggles.’

Turns out I had the overdrive backwards. 21 spline is a 70. 23 spline is a 75.

Everything you ever wanted to know about the AW4

I've gotten enough questions concerning AW4 specs and "will x year AW4 fit into x year XJ?" that I figure I should probably just write it all up once and for all... so here goes! The AW4 transmission was used in 4.0L equipped XJs from 1987 through 2001. It was also rarely used in 2.5L equipped...
www.naxja.org www.naxja.org

Year splits, aka "will this transmission fit my XJ?"
  • 1987-1990, the AW4 had a 21 spline output shaft, a 1 pulse per revolution reed switch Output Speed Sensor, no Input Speed Sensor, and a 0.705:1 OD ratio. 4.0L and 2.5L transmissions are fundamentally the same, except for the torque converter and bellhousing, which are unique for each motor.
  • 1990 and earlier transmissions have a different style and length TV (throttle valve) cable from the 1991 and later unit. This is due to the difference in throttle bodies and linkages.
  • 1990.5-1996, the AW4 switched to a 23 spline output shaft and a 0.75:1 OD ratio. It was no longer available behind the 2.5L engine. Otherwise, it remained exactly the same.
  • 1991 and later AW4s have a new style and length of throttle valve cable to accomodate the changes from the RENIX throttle body and linkages/brackets to the new HO throttle body and linkages/brackets.
  • 1997, the AW4 is exactly the same as the 1990.5-1996 units, except the electrical connector for the wiring harness changed. A simple cut and splice will solve this problem.
  • 1998-01, the AW4 changed electrically, but is otherwise the same as 1990.5-1997 units. The Output Speed Sensor changed from a 1pps reed switch to a 4 pulse/rev variable reluctance pickup similar to the RENIX CPS and most ABS wheel speed sensors. A 16 pulse/rev Input Speed Sensor was also added. The ISS and OSS for these years are the same part number; one may be substituted for the other for spare parts purposes.
NSS:
  • 1987-1996 the NSS is the same. Positions for R, P/N, 1-2, and 3. No connections indicates that the shifter is in OD - OR that the NSS is dirty. The TCU can't tell, this can lead to some common transmission shifting symptoms.
  • 1997-2001 the NSS wiring harness connector is different but the internals are the same - mostly. There is now a circuit for each gear position (1-2, 3, D) on the switch and an extra wire for the new position. This was added to improve feedback to the TCU and likely also to allow the TCU to definitively throw a DTC code if it sees no contacts shorted, which now indicates a bad NSS rather than "bad NSS or overdrive gear, we don't know."
Click to expand...
 
So did you wind up with a 21 spline 242? I'm confused. Or are you just bummed to find the .75 OD ratio?
 
23 spline everything.
I was just saying I could put the 21 spline input I’m replacing in the 242, and have a back up trans/TC combo.
 
I drove my Cherokee briefly on 37s with 4.56 gears in stock axles and it was a total dog. That was on flat ground too. Crawling with a 4:1 tcase was fine though off road.

Don’t fear the gear. I even had 31s on my Cherokee at one point with 4.56 gears. DD that set up for years going 70 mph never had a problem. Like others have said it is probably better to try and keep some of that strain off of the AW4 while it is locked up by gearing deeper. 4.88s might be okay but I would plan on putting a oversized transmission fluid cooler because that transmission will be shifting a lot with any resistance.
 
No question, go 5.38s over 5.12s. You are always going to go bigger on the tire, never smaller.
 
gozuki said:
No question, go 5.38s over 5.12s. You are always going to go bigger on the tire, never smaller.
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You can’t lose with 42s.

Edit: I don’t ever see myself goi g to 42s with this. 40s are enough and I’d rather stick with what I know than go bigger just to say I have 42s or 44s and redo everything.

I don’t know anything about gearing or tire sizes beyond what a chart tells me. I’d like to retain the ability to drive down the highway at 65 without the engine screaming at me. I also don’t know how much of a difference I’d see between 5.13 and 5.38s in crawling or city driving. It’s roughly a 5% difference. Am I even going to notice it?

4.1 vs 5.38 sure. Big difference.
 
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I was on 33s with 4.56s. Worked great, driveshaft has to be well balanced though, it’s spinning super fast.

You’ll want shorter than stock RPM for certain. 40s weigh a lot and will sap power just trying to turn.
 
RunningProblem said:
You can’t lose with 42s.

Edit: I don’t ever see myself goi g to 42s with this. 40s are enough and I’d rather stick with what I know than go bigger just to say I have 42s or 44s and redo everything.

I don’t know anything about gearing or tire sizes beyond what a chart tells me. I’d like to retain the ability to drive down the highway at 65 without the engine screaming at me. I also don’t know how much of a difference I’d see between 5.13 and 5.38s in crawling or city driving. It’s roughly a 5% difference. Am I even going to notice it?

4.1 vs 5.38 sure. Big difference.
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4.0 likes to spin. Like I said I used to drive 3k rpm in OD for hours at a time. Zero concerns.
 
I pulled the transmission. It was smoother than I remember. I also remember the install taking a shit ton more work than I ever wanted to put in.


I have to take the transfer case apart to put in the new to me input. I should have drained the fluid while it was in the jeep.


The thing no one told me about 40s is how many new problems they create. The transmission Jack didn’t go high enough to support the transmission. I had to take the wheels off, put the jeep on 12 ton Jack stands, and put the axle on some 2 or 3 ton jacket stands
 

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Lol similar to what I just experienced, but not cuz of 40s. I just had it high on Jack’s, put a block on the trans jack to reach, but then once it was down the block made the trans too tall to go under the “frame” so I had to carefully slide it off the jack. Then reverse that and figure out how to lift it on the jack under the Jeep
 
harbor freight has big heavy duty tranny jack, i have the small one and it worked good, but borrowed my buddies HD one that fucker will jack up 24 plus inches off the ground. just fyi
 
chaplinfj60 said:
harbor freight has big heavy duty tranny jack, i have the small one and it worked good, but borrowed my buddies HD one that fucker will jack up 24 plus inches off the ground. just fyi
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I have it. Works great. I trashed the brackets and welded some D-rings to the sides and throw the trans on top with some cribbing and a strap to hold it in place.
 
chaplinfj60 said:
harbor freight has big heavy duty tranny jack, i have the small one and it worked good, but borrowed my buddies HD one that fucker will jack up 24 plus inches off the ground. just fyi
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I’m using the 800 pound one because I didn’t think I’d need the 2,000 pound one. This has a 22 1/2” max lift height. I guess I need to remember everything has to go to 24” now.

I did learn why I WOULD NOT want the off road Jack as my primary Jack. When I was jacking up the axle I had to rotate the Jack with weight on it. I’d have to have more space for the off road Jack since it only goes forward/backwards.


Edit: the 2,000 pound transmission Jack has a max height of 30 3/4”. :homer:
 
chaplinfj60 said:
harbor freight has big heavy duty tranny jack, i have the small one and it worked good, but borrowed my buddies HD one that fucker will jack up 24 plus inches off the ground. just fyi
Click to expand...
Good to know, I have the same small one in the pics.

the minimum height matters too though
 
fl0w3n said:
Good to know, I have the same small one in the pics.

the minimum height matters too though
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I guess I don’t think of minimums when I’m already 2 ft off the ground. I’m sure it was a problem when I had 33s and rock sliders sticking down.


Not to self….a 2 post lift is awesome.
 
23 spline swap mostly complete. I need to put fluid in the transmission and transfer case, then install driveshafts and maybe check and make sure it’s all torqued.


Checking the pan for scrap metal chunks.
D99FFABA-D6D5-499D-9D11-431F974A3356.jpeg



Installed.
7A91766E-410F-49E4-AC79-0747AEE078B0.jpeg
 
I’d only go to a rubicon case if I found one for a good deal AND I could replace the yoke on it. I’m 1350 at the transfer case and a rubicon case is 1310. It MIGHT be the same spline count front and rear as my current case, but if it isn’t then I’m stuck with 1310 joints at the case where probably most of the torque will be applied. Yes it creates an easily repairable weak point. I just don’t think 40s and 1 tons are what the engineers had in mind when going 1310 on the yokes.

Edit: there is also the problem of my speedometer gear no longer working, and the shift linking needing to be replaced. The 241OR shift pattern is the opposite of the 231. Novak sells a shift conversion kit for about $180, and I think a few companies make 1350 holes ( Adams driveshaft) I could used since the rear is a 32 spline. But again it’s just ‘a couple hundred bucks’ for each part added to the cost of a 241OR just to get it to work.
 
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Another option is this…a mechanical drive speed convertor for $400 from Jegs.

JEGS 41800: Mechanical Speedometer Converter with Built-in GPS - JEGS High Performance

Order a mechanical speedometer converter with a GPS online from JEGS High Performance. This electric to mechanical speedometer cable drive conversion kit fits Ford, GM or Chrysler speedometers and is easy to install. Visit JEGS High Performance and buy a SpeedBox speedometer for your vehicle now!
www.jegs.com www.jegs.com

JEGS SpeedBox is designed to operate a cable-driven mechanical speedometer using an electric speed signal from GPS, CAN-Bus speed data through the OBD II or Vehicle Speed Sensor (VSS). The SpeedBox can be installed in the dash or under the hood.

Special Note:

The SpeedBox is not Waterproof
Click to expand...
 
RunningProblem said:
I’d only go to a rubicon case if I found one for a good deal AND I could replace the yoke on it. I’m 1350 at the transfer case and a rubicon case is 1310. It MIGHT be the same spline count front and rear as my current case, but if it isn’t then I’m stuck with 1310 joints at the case where probably most of the torque will be applied. Yes it creates an easily repairable weak point. I just don’t think 40s and 1 tons are what the engineers had in mind when going 1310 on the yokes.

Edit: there is also the problem of my speedometer gear no longer working, and the shift linking needing to be replaced. The 241OR shift pattern is the opposite of the 231. Novak sells a shift conversion kit for about $180, and I think a few companies make 1350 holes ( Adams driveshaft) I could used since the rear is a 32 spline. But again it’s just ‘a couple hundred bucks’ for each part added to the cost of a 241OR just to get it to work.
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It appears that you can replace the yoke on 241OR. If you have a deal on one, definitely go for it. Yokes are cheap.
 
Locally an NP205 is like $600 and to make a doubler it’s almost worth buying a rubicon case to have something more ‘bolt on’ at which point it’s JUST another $1,500 for an Atlas, and I’ll still need numerically higher gears. It might be smarter to buy gears first.
 
RunningProblem said:
Locally an NP205 is like $600 and to make a doubler it’s almost worth buying a rubicon case to have something more ‘bolt on’ at which point it’s JUST another $1,500 for an Atlas, and I’ll still need numerically higher gears. It might be smarter to buy gears first.
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If only you knew someone who had a 203 taking up space in his garage...
 
Just go wheel it, it’s not like you can’t as is. Don’t let that stop you. When you can, I would probably gear it first. Then go from there.

Maybe do some shift lockout switches so you can stick to 1st.
 
M92PV4U said:
If only you knew someone who had a 203 taking up space in his garage...
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HE couldn’t have told me that when HE hung out with me last year so HE is on my shit list.
Plus it’s probably chevy crap I can’t use because driver/passenger drop nonsense. It WOULD help web wheeling to say I have a 203/205 doubler until someone asks how it works with a Ford axle and a Chevy transfer case. :lmao:
 
RunningProblem said:
HE couldn’t have told me that when HE hung out with me last year so HE is on my shit list.
Plus it’s probably chevy crap I can’t use because driver/passenger drop nonsense. It WOULD help web wheeling to say I have a 203/205 doubler until someone asks how it works with a Ford axle and a Chevy transfer case. :lmao:
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Oof... you need more cardin joints in your front driveline :flipoff2:. Yeah I have all chevy stuff.
 
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