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engine/tranny swap

RenegadeT

NAXJA Forum User
Location
GSO, NC
I just picked up a '91 XJ 4.0L/AW4 4x4, somethings wrong with the transmission, mechanical issue, I can hear an internal rattling by flex plate/torque converter and it doesnt seem to build pressure. The fluid is brand new red, and if anything, its overfilled. PO said it needed a torque converter and filter.
The odo shows 275k (PO said the PO^2 swapped an engine in 2-3 years ago, not sure if I believe that). This engine has some blowby issues, oil all over the valve cover and in the airbox. I checked the compression (112, 109, 130, 136, 135, 110 psi), not as bad as I expected actually.

I have another trail-only '95 XJ 4.0L/AW4 4x4, and really the only good thing left on it is the 4.0L/AW4 combo. 160k on the odo, engine compression is slightly higher (125, 131, 134, 130, 129, 111 psi). The body/chassis is trashed, I will be pulling the engine/tranny out abd scrapping it.

I am thinking it would be best to put the '95 4.0L/AW4 into the '91, instead of trying to swap just the transmission. Will this be plug-n-play, or is there any differences between 1991 and 95? Do the ECU and TCU need to stay with the original components?

FWIW, the only good transfer case (NP231) I have is on the back of the bad '91 AW4.
 
Both the 1991 and 1995 should be the HO engines with the Chrysler OBD-I controllers. Everything should be a straight bolt up. Keep the 91 ecm and tcu. You checked that the t/c is still bolted to the flexplate?
 
havent inspected the TC/flexplate yet. Either it is bolt up or it isnt right? The tranny acts like it needs to build up a little pressure before the engine starts pulling. Once it starts rolling, it seems good.
 
Check the torque converter to flexplate bolts, they work loose. Use a bright light and a pry bar and see if you can detect any cracks in the flexplate, they like to do that.

Adjust the throttle pressure cable--it effects the amount of pressure available to the valve body at different throttle positions.
 
Dropped the 95 engine/tranny in the 91XJ today, found 3 differences between the connectors/sensors.
1- Oil Pressure sender.
2- Coolant temp sensor (on the rear of the head)
These two are fairly easy, I'll unscrew the old sensors and put them on the good 95 engine.

The third is a the CPS on the bellhousing. I wish I noticed this when the engine was hanging on the cherry picker, it would have been much easier to swap then.
Is it as simple as just pulling the 95 CPS from the 95 engine, then installing the 91 CPS in the 95 engine? The connectors are differnet, I'm not sure if thats it.
I think I've got most of the electronics hooked up now, except the ECU/TCU's and starter. Is there anythign else that might be different?
 
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