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th 400 swap

crutch

NAXJA Forum User
Location
levelland, tx.
I have been given a amc th 4oo transmission from a friend and was wondering if any one has done this swap. I have a 93 xj with ax 15 tranny. the tranny also came with an adapter for 231. Any feed back would be helpful.
 
It is 1.5" longer than my ax15, I'm also doing a box for rocks doubler kit, so I was planing on new driveshafts anyways. I also planed on running a manual valve body. i just hope that adding 400, 231, and dana 300 will not be to long
 
I wouldn't mess with a manual valve body. They work pretty good on a dragster, but they're kind of a PITA for a street rig. The manual kit usually increases line pressure, allowing tighter clutch/band lockup, but that's not really necessary behind a 4.0L. with 200-odd HP.
 
The good news is that it should bolt up once you get a flex plate drilled for the torque converter. All of the AMC 6s and 8s share the same bell housing pattern. Very handy.
 
I would start with a flex plate from the AW4 and a flex plate for the TH400 as well (for cheap, say the JY?). Compare the two and get the advice from an automotive machinist on how to modify the AW4 plate. I would also look at the relative positions of the flex plates as compared to the bell housing mounting points.

Be very careful with this. The engagement of the Torque Converter to the pump has a narrow margin of error. In too deep and it will destroy the pump.
 
Thank you for the info. I talked with a mech today and he thinks that a flex plate from the original jeep that the 400 came out of should fit my 93 xj. I'm not so sure, I will just need to do some more research.
 
The 4.0 flex plate carries a stator ring for the crank position sensor. If you're going to use a flex plate from a non-injected jeep, you'll have to affix the stator ring to the new flex plate. Probably easier to mod the 4.0 flex plate to bolt up the TH-400 converter. Also going to have to drill the TH-400 bell housing to accept a 4.0 CPS.

There's a kit to move the CPS to the front of the engine. It costs a couple hundred bucks, but it would solve both problems.
 
I was planing on using the kit from hessco, and moving it to the front of the crank. I did some research last night trying to find out what year and make that the th400 came in. All I could find was that it came in the grand wagoneer but no year model. The guy I got the 400 from said he thought it came out of a cj, but I'm not for sure that it did. Thanks for the info.
 
I found out that the fly wheel for a 75 cj has the same number of teeth, same teeth pitch, and same od as the flex plate that is in front of my ax 15. So now I just have to drop my tranny and check the id of the crank, and the od of torque converter.
 
Point of information... Last time I checked, the AX-15 is a 5 speed manual transmission. That being the case, there is a flywheel with a clutch not a flex plate with a torque converter. If you have the auto, you already have the flex plate as it is an AW4 as it was used from 1987 through to the end of production...

The flex plate from a 4.2 will fit as that crank is used by the Stroker Crowd without issues.
 
The trans may have come out of a CJ.

AMC offered a pretty weird drive train option in the late '70s. It was called "QuadraTrac"
Had a Borg-Warner full time 4wd transfer case,(with an optional bolt on low range unit) that had passenger side offset front and rear drive outputs similar to the old Dana-18 T-case.
The QuadraTrac system was only available with an automatic, which was the TH-400. While not exactly rare, it is kind of uncommon.
 
Well AMC... the
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AMC did a number of strange things mixing Ford and GM parts on a regular basis. AMC grew out of Nash after Nash (remember the Rambler?) purchased the dying Hudson Corporation. Nash started on the "adopt what works" concept at that point lifting the entire front suspension from the Hudson along with the "Monobuilt" frame/body that Hudson pioneered. We call it "Unibody" today. Invented, by Hudson, circa 1950. And yes, I have been a proud owner of a 1953 Hudson Hornet with the Twin-H Power option on my 308 cuin (thats a 5.05L) Flat Head inline 6 with a 4 speed Automatic behind it. My first car... And no, I will not admit to just how early in the 60s that was...
 
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