AW4 Transmission Swap

['89_Wagon]

Looking into transmission coolers... I'm thinking of getting something in the 20k-26k BTU range. Is that overkill or not enough?

['89_Wagon]

Similar reasons here for keeping the NP229. My vacuum shifter works well for now.

But...the vehicle speed signal for the TCU comes from the 242 VSS. I'm not sure yet how I will handle that. Originally I figured I'd just replace my speedometer with a not-cable driven unit, but I just fixed my cruise control and that gets it's speed signal from a speedometer cable in-line vss.

Either way I figure I will have to create a VSS, either for my cruise or for the TCU.

I could be wrong, but I think the VSS for the AW4 is near the output shaft of the AW4 and not the NP242. This might be different depending on the year. But, this would make sense to me based on the harness and transmission I have sitting in my garage. Technically, it's the trans output sensor.

Check out the pictures in this link.

https://www.cherokeeforum.com/f2/transmission-speed-sensor-location-243436/

[yossarian19]

Looking into transmission coolers... I'm thinking of getting something in the 20k-26k BTU range. Is that overkill or not enough?

Overkill.

Plumb it through the radiator, for sure, and add a small cooler (think OEM sizing for a similar rig)
It's easy to go overboard here. What you want to remember is that a transmission has a designed operating temperature the same as an engine and that the lower tank of the radiator, lo and behold, is about that temperature.
Somebody chime in if they can show me wrong, but colder is not always better on a trans.

['89_Wagon]

Overkill.

Plumb it through the radiator, for sure, and add a small cooler (think OEM sizing for a similar rig)
It's easy to go overboard here. What you want to remember is that a transmission has a designed operating temperature the same as an engine and that the lower tank of the radiator, lo and behold, is about that temperature.
Somebody chime in if they can show me wrong, but colder is not always better on a trans.

Do you know what thread size the fitting is on the radiator?

Edit: seems like 1/8 npt... Will test. I've read the aw4 runs hot but could I just run it with the radiator cooler only? I do not plan on towing but do plan on many drives through the white mountains with camping gear which has some steep grades

[rocklaurence]

Regarding Trans fluid temps, I bypass the radiator on all my vehicles because the engine is running at 195/210 degrees and the danger zone for a trans is 220. With a separate cooler of 24000 GVW they run at approximately 160-180 degrees and under heavy use approach 200. I dont live up north and dont need to concern myself with startup temps bellow zero but you can control the temps somewhat with a controlled aux' fan. It wouldnt turn on until after reaching a higher temp. Ive worked around hydraulics all my life and if any of it gets to hot to touch--its getting too hot.
Note: I had a 93 Ford with A4LD electronic trans and it would get hot and puke the fluid out during Off Roading. This left me stranded twice at the worst possible time. I resolved the issue by bypassing the radiator and it never did it again and the were no negative effects to running it cooler.

['89_Wagon]

Appreciate all the advice on coolers. I've leaning towards routing it through the rad and then to an external cooler, like the OEM setup. If it didn't get so cold where I live, which it often does, routing to just an external cooler would make sense just to keep things simple and get the lowest temps.

The AW4 I bought came with a Hayden 24K GVW cooler so that's what I'm using. Maybe overkill but I'm thinking with the bottom of the radiator temp at 180, the trans fluid temp might drop to 160 by the time it exits the external cooler. Operating range for the AW4 is 125-176 so this setup seems good.

Bought more parts.... mostly fittings, lines, and clamps. Will post some pics. So far, I've spent ~$650. Big items were the transmission ($200), wiring harness ($100), and spacer ($75). All the little stuff adds up quick! I'm sure buying a parts jeep would have been less costly, but there's no way I could have one in my yard and be happily married .

[Mikel]

For those with AW4s, other than having an overdrive, how do you like it compared to the 3 speed auto it replaced? (in terms of gear ratios, gear spacing, shift patterns, lock-up in the lower gears...)
Thanks.

[yossarian19]

I haven't driven mine in the SJ much at all yet. In XJ vehicles with the 4.0, I've got a *ton* of miles driving them.
First gear is a bit deeper than the TH400, second is darn similar and third is the same.
Lockup in lower gears is seamless, I can't think of a time I've really noticed it.
The only obnoxious thing is that when you put it in 1-2 (first two gears are in a combined shifter position) it will wind out to like 5000 RPM before it shifts to second. There are modifications to fix this, so you can select full automatic or lock it in a specific gear. But then, how often have I wanted to lock it in second? Like... maybe once or twice, in ~12 years of driving rigs with AW4 transmissions. It's a very specific off-road-only use case where that is annoying.

['89_Wagon]

This swap will move the transfer case 4 inches back. I read a bit about clocking axles for double cardan joints, which would apply to the front axle. Is this something that needs to be done?

[pickledtoast]

4" eh. I'm getting no where near that with my tape measure, but you are further along than I am.

['89_Wagon]

4" eh. I'm getting no where near that with my tape measure, but you are further along than I am.

Honestly, I haven't confirmed that yet. I just remember reading that somewhere. What measurements did you get? I plan to start the actual swap later this week.

[rocklaurence]

Dont try and Clock the front axle to meet the CV because it will likely make too big of a change to the Caster. The rear axle can be clocked without issue.

[pickledtoast]

Honestly, I haven't confirmed that yet. I just remember reading that somewhere. What measurements did you get? I plan to start the actual swap later this week.

I was getting almost the same, until you pointed out we need the 7/8 spacer to reuse the NP229. So now I have 7/8" further rearward.

That's me measuring bellhousing to transfer case flange with a tape measure on the A727, not very accurate. (I digitized the aw4, it's 25.300" bellhousing to transfer case flange). But I shouldn't be 4" off.

['89_Wagon]

I was getting almost the same, until you pointed out we need the 7/8 spacer to reuse the NP229. So now I have 7/8" further rearward.

That's me measuring bellhousing to transfer case flange with a tape measure on the A727, not very accurate. (I digitized the aw4, it's 25.300" bellhousing to transfer case flange). But I shouldn't be 4" off.

I did not measure my A727, but grabbing the length from advanced adapters and Novak sites, here's what I come up with in inches for the relevant pieces. I'll tape measure as well just to confirm.

A727
Transmission Length: 22.625
Total Relevant Length: 22.625

AW4
Transmission Length: 25.375
Adapter: .875
2-Transfer case gaskets: .125 (optional?)
Total Relevant Length: 26.375

Difference = 3.75

Here's a link to advanced adapters A727 length.

https://www.advanceadapters.com/tech-vault/torqueflite-727/

AW4 length link

http://www.novak-adapt.com/knowledge/aw4

EDIT: Measured the AW4, A727, adapter+gaskets and the values above check out.

[pickledtoast]

Yeah you're right. I just rough tape measured my A727 at around 23", so that 22.625 value is probably right. I don't know what kinda crack I was smoking before.