Overdrive Transmission Options?

[MysticRob]

Being a fan of originality and believing you can improve upon that which already exists, I've been looking into ways of improving mileage on my stock drivetrain 88 GW.

Obviously fuel injection is a good way to ensure proper operation, but being that I want to continue using the original 360 engine, I know doing a transmission swap is the best way to lower RPMs and save on gas over our 3-speed 727s.

Problem is, there isn't a lot of info I've seen on fitment and retrofitting of more modern overdrive transmissions in our rigs. I know there's a 360 block used in some 1998 Grand Cherokees and Durangos, so will those 4-speed overdrive transmissions work behind our rigs or are the mounting holes different? Or is that a different block (aka Chrysler vs AMC) altogether?

What other four or even five speed tranny is available, what's "easy", and what else would need done to swap?
Can the NP229 I have be reused? Is there a better xfer case option with an overdrive tranny option?

I'm looking for "as plug and play as possible", wouldn't mind going with a resized drive shaft, but don't really want to swap out much else or have things fabricated.

Any good info out there beyond the search function not really showing me much?

[tgreese]

Isn't that the Chrysler LA 360? A '98 ZJ could come with a 318, and the Chryco 360 is an upsized version of that. Different. As I recall, some have used the AW4 from an XJ. The WJ Grand Cherokee used the 42RE, a 4-speed overdrive descendant of the 727, with the 4.0L which should be the same bell pattern as your 360. You'd need to work out a flex plate to fit and balance the 360, and the 42RE is electronically controlled - so you'd need some kind of controller. The 42RE in the WJ does not have a stellar reputation for durability, but apparently they can be built to remedy that.

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

[MysticRob]

Isn't that the Chrysler LA 360? A '98 ZJ could come with a 318, and the Chryco 360 is an upsized version of that. Different. As I recall, some have used the AW4 from an XJ. The WJ Grand Cherokee used the 42RE, a 4-speed overdrive descendant of the 727, with the 4.0L which should be the same bell pattern as your 360. You'd need to work out a flex plate to fit and balance the 360, and the 42RE is electronically controlled - so you'd need some kind of controller. The 42RE in the WJ does not have a stellar reputation for durability, but apparently they can be built to remedy that.

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

I just know there's a spec'd up ZJ that came with a 360 in 98 (and special awesome hood vent extractors, LOL), but figure it's the mopar unit, and not an AMC.

I've read the A518 / 46RH is a 727 with an overdrive gear on it, and doesn't require a controller, but would require a different length shorter drive shaft.

I did see a couple mentions of the AW4, which apparently works well, but requires some adapters, etc.

I can see why many people just completely swap out the engine and transmission both, doesn't seem like many easy tranny options to improve mileage.

[J20 project]

1998 Grand Cherokees and Durangos, so will those 4-speed overdrive transmissions work behind our rigs or are the mounting holes different? Or is that a different block (aka Chrysler vs AMC) altogether?




Yur kidding right?..you believe a 70 dodge tranny will bolt onto a 360/5.9 AMc?
\\\\


Good luck sir.

[MysticRob]

1998 Grand Cherokees and Durangos, so will those 4-speed overdrive transmissions work behind our rigs or are the mounting holes different? Or is that a different block (aka Chrysler vs AMC) altogether?

Yur kidding right?..you believe a 70 dodge tranny will bolt onto a 360/5.9 AMc?
\\\\


Good luck sir.

I don't believe anything, hence the word "will" I used in the form of a question.
I know our GWs came with a 727 transmission, which was a Mopar unit, correct? If that tranny worked behind both the AMC And Mopar engines, would a later model Mopar overdrive unit also work behind our 360s?

EDIT: I found this pdf site that specifically mentions the AMC/Jeep 727 not being interchangeable with Mopar engines, so sounds like the later Mopar overdrive units likely won't work on an AMC 360. Too bad, but will do more research.

https://www.novak-adapt.com/knowledge/transmissions/automatic/727

"The reader should be aware that the AMC versions of the 727 transmission will not interchange to Mopar engines. The bolt pattern *looks* quite similar, but is not."

[crazydog]

Being a fan of originality and believing you can improve upon that which already exists, I've been looking into ways of improving mileage on my stock drivetrain 88 GW.

Obviously fuel injection is a good way to ensure proper operation, but being that I want to continue using the original 360 engine, I know doing a transmission swap is the best way to lower RPMs and save on gas over our 3-speed 727s.

Problem is, there isn't a lot of info I've seen on fitment and retrofitting of more modern overdrive transmissions in our rigs. I know there's a 360 block used in some 1998 Grand Cherokees and Durangos, so will those 4-speed overdrive transmissions work behind our rigs or are the mounting holes different? Or is that a different block (aka Chrysler vs AMC) altogether?

What other four or even five speed tranny is available, what's "easy", and what else would need done to swap?
Can the NP229 I have be reused? Is there a better xfer case option with an overdrive tranny option?

I'm looking for "as plug and play as possible", wouldn't mind going with a resized drive shaft, but don't really want to swap out much else or have things fabricated.

Any good info out there beyond the search function not really showing me much?

As has been said, the 727 used in FSJ's has a specific case to bolt to the AMC block. As does the TH400 used in the 70's.

Here is how @ristow adapted a Mopar OD transmission to an AMC block.

http://www.ifsja.org/forums/vb/showthread.php?t=51307

If you want an overdrive automatic transmission you can use adapters from Novax to attach a 700R4 to the AMC block and the stock NP transfer case.

https://www.novak-adapt.com/catalog/adapters/transmission-to-transfer-case/th700r4-to/kit-137/

https://www.novak-adapt.com/catalog/adapters/engine-to-transmission/amc/kit-437amc/

[MysticRob]

Ah, very bueno post, thank you!
I'd seen mention of Novak in another thread, but had no idea how much stuff they had available. I'll research them and do a cost analysis. Likely will stay with the ancient 727 and NP229 for a while till they need rebuilding/replacing.

[SC/397]

Like mentioned above...
A dodge/cryco 360 is NOT an AMC engine no more than a ford 360 is a AMC engine.
Any transmission that will bolt up to the 4L AMC Jeep engine will bolt up to the AMC V8 engines.

The two automatic overdrive choices for direct bolt up to the AMC V8 and go are the Aisin AW4 or the chrysler 500SE.
I am a believer in the AW4. It is the best automatic transmission I have ever ran.
I have one in my Javelin that works great. Other than these two transmissions, you will have to use an adapter kit.


AW4 Aisin Warner Aluminum 4 oil/water 242 (4.0) 1987–2006 Jeep

500SE (42RE) Chrysler Aluminum 4 oil/water 242 (4.0) 1993–2004 Jeep

['89_Wagon]

I have a AMC 360/aw4/np229 setup with 3.31 gears and it works well. Also running a GM style TBI. I have not measured the mpg. I did the swap for similar reasons the OP did it for. One thing I don't like about it is the shifter situation. Unlike GM transmission swaps, there's no off the shelf solution so I just used a u-clamp to hold the shifter linkage together. So far, it's fallen apart once. I'm sure there's a better way though. I have a AW4 swap thread on here if you're interested.

With all that said, I'm pretty sure my engine has piston slap so faced with rebuilding the 360 or going LS, I'm going LS with a GM 4 speed.

[tgreese]

...
I've read the A518 / 46RH is a 727 with an overdrive gear on it, and doesn't require a controller, but would require a different length shorter drive shaft.
...

I would expect any of these swaps would need new driveshafts. If not mentioned, it's because it's so obvious. More speeds implies more guts in the case and a longer case. Plus the car companies have no reason to make different transmissions the same length.

[80Limited]

I have done the AW4 it is worth it.

[MysticRob]

I have done the AW4 it is worth it.

It's funny I'd never heard of an AW4 before buying my GW, so imagine my surprise when I discovered it's short for Aisin-Warner, both of which I've heard of separately.

I shall research this some more and see if I can figure out how to economically swap at some point.

[80Limited]

I have a thread here on the site of what I used.

[80Limited]

I think the thread is: AW4 swap complete.

[fastjeep]

Has anybody looked into the 6L80 from GM. Has chevy bell pattern so adapter to AMC engine thru Novak or AA. Novak has adapter to Dana 300 or NP 208 in fsj transfer. There is a controller now to operate the electronic valve body that only needs a rpm and tps signal from any engine so with Fitech injection I have on my J10 will fill those signals. The 6L80 has a 4.02 first gear for great starting torque and 5th and 6th gears are overdrive lowering cruise rpms. The trans are found in 07 to 14 various models as silverados and escalades and corvettes ( are rear mounted to transaxle ) I have one from a caprise police unit that was crashed. Will need to go to a floor shifter as column will not have the required detents. You can also use paddle shifters if you want to. The over all length is only about 2 inches longer than 727 trans.