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Engine swap with AW4

The Merg

NAXJA Forum User
'95 XJ (~180k) with AW4, getting a 4.0L (126k) from a '92 and a 231 from a TJ...

I know nothing about autos, all my Jeeps have been manuals up to this point. So:
What do I need to watch out for?
Anything I should look at/fix/replace while it's out?
Do I need to do anything with the torque converter before bolting everything back up?
Should I clean the NSS while the trans is out and then adjust it when everything's hooked up? Or just wait?
 
A torque converter is not a clutch, so don't install it like one. It goes in the transmission all the way, all 3 or 4 sets of splines, until it won't go any further. Then bolt the trans to the engine. A quick check: without drawing the two together with bolts, do the trans and engine mate completely, leaving the converter to come back forward a little bit to the flexplate? If not, the converter is not seated all the way.

It's a simple thing, but it gets done wrong. A lot. That gets expensive.

My preference would be to install the engine/ trans as a unit then put the tcase on.
 
Thanks, I'll make sure to be careful. I haven't actually removed it from the trans, and won't unless I have to.

Do I need to/should I replace the fluid in the torque converter?

The whole thing came out without too much effort (save me forgetting to unbolt the fuel line bracket from the intake manifold - thank god for donor XJs). Having a hoist and 3 extra sets of hands makes yanking and reinstalling drivetrains much easier
 
Hey Greg,

The torque converter will fall right off the transmission if you don't remove it. You need to remove it to keep it from falling off.

The fluid in the converter is the same as what's in the rest of the transmission. Basically an automatic uses a pump to spray fluid into the torque converter, as pump speed increases the fluid force increases, which creates the power for the rest of the transmission. You can drain the converter and it will fill up again with fluid from the pump. You don't need to do it though, and it can damage the converter in the right scenario, so leave the fluid in it is safest. You should do a fluid swap and replace the filter while everything is out. It's a pain to drop the pan for filter when it's in the jeep.

One thing to pay attention to is the size of the shaft between the transmission and transfer case. The spline count changed once but the shaft depth changed a few different times. Here's the reference thread http://www.naxja.org/forum/showthread.php?t=1053970

Also some of the Wranglers used a different clocking of the transfer case I think, might check to make sure the bolt holes are in the same position
 
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That's a good call, also replace the water pump if you can, and check the harmonic balancer. I also replaced the gasket on the oil pan, manifolds, and valve cover when I had mine on the stand. Hopefully I won't need to service anything on it for another few years
 
You can drain the converter and it will fill up again with fluid from the pump. You don't need to do it though, and it can damage the converter in the right scenario, so leave the fluid in it is safest. You should do a fluid swap and replace the filter while everything is out. It's a pain to drop the pan for filter when it's in the jeep.

Thanks, Eric, I was hoping you'd see this.

I was planning to replace the fluid and filter in the trans, but I've heard lots of weird things about the fluid in the torque converter so I had to ask (essentially the bolded above, but I think I distorted it in my head). Like I said, I know close to nothing about autos.

Motor is getting a full gasket replacement, including RMS. I'm swapping the brand new water pump from the other engine.

NP231: Looks like I'll be fine? But I'll cross that bridge when I come to it. I'll inspect and compare both cases thoroughly to make sure.
 
Eric was right, input shaft on the transfer case is too long. I'm going to throw the original one back on there, build some new linkage, and hope that was the problem.


Can anyone give me a quick rundown on what I need to/should/shouldn't remove if I take out the AC? I do plan on OBA down the road if that matters - not any time soon, though.

Also, it turns out the fuel lines on my donor XJ are trash, too. Time to hit the junkyard.
 
For the A/C you should have the system evacuated somewhere, disconnect the hoses from the compressor and the evaporator pipes going through the firewall, then plug them off until they are going to be used again. You can pull out the rest of it, including the condenser in front of the radiator (might be able to sell that).

Any decent shop should be able to bend up hard line for the fuel supply
 
Almost finished, it started and ran today. Just gotta button a few things up, fill fluids and such.

I've got a few plugs I can't account for, can anyone help me out? Sorry for the bad cell pictures.

plug #1, on the driver side of the transmission
IMG00066-20110417-1749.jpg


Plug #2 and #3, passenger side of the engine bay. They appear identical
IMG00065-20110417-1748.jpg



And then there's this thing... thought it was a horn, but it's not. Might be a speaker of some kind?
IMG00062-20110401-1443.jpg
 
If the connector on the side of the transmission is s a yellow/black and red/black pair then it's the plug for the full-time light are for the 242. Tuck it behind the plate.

One of the plugs might be for hood lamp. Or if you have disconnected the A/C then they might be for the compressor and/or low-pressure refrigerant switch. The cruise control server is usually on the passenger fender wall too if you don't have that. Maybe the battery temperature sensor? Could also be the connector for the outside temperature sensor (looks like it with the red connector, actually). What year and model is the engine wiring harness?

That looks like an air horn to me
 
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If the connector on the side of the transmission is a yellow/black and red/black pair then it's the plug for the full-time light are for the 242. Tuck it behind the plate.

One of the plugs might be for hood lamp. Or if you have disconnected the A/C then they might be for the compressor and/or low-pressure refrigerant switch. The cruise control server is usually on the passenger fender wall too if you don't have that. Maybe the battery temperature sensor? Could also be the connector for the outside temperature sensor (looks like it with the red connector, actually). What year and model is the engine wiring harness?

Neither of those plugs is the A/C, that's a different one-wire plug. I have cruise control; I'll check it, although I don't know why I would have unplugged it.
Battery has no sensors that I can see. I don't have an overhead console, so outside temp sensor could make sense.

The wiring harness is the stock '95 XJ harness. I basically only swapped block and head, pretty everything else was retained.

That looks like an air horn to me

I thought so too, but trying to power it produced nothing but crackles. :confused:



For the A/C you should have the system evacuated somewhere, disconnect the hoses from the compressor and the evaporator pipes going through the firewall, then plug them off until they are going to be used again. You can pull out the rest of it, including the condenser in front of the radiator (might be able to sell that).

Does anyone sell any sort of pulley that I can put in place of the compressor? Seems silly to leave it there. Or can I move the alternator up?


Any decent shop should be able to bend up hard line for the fuel supply

Found the lines from the parts XJ, thank god. *victory*
 
Dorman makes A/C bypass pulleys but not for 94-95 (refrigerant changed from R12 to R134a in 94, and the serp belt setup changed a bit in 96). You might be able to fit the 93 or 96 pulley if you can convince Autozone or Advance to order them and let you compare the compressor bolt patterns.
 
If the connector on the side of the transmission is s a yellow/black and red/black pair then it's the plug for the full-time light are for the 242. Tuck it behind the plate.

That was it, yellow/black red/black.
I also realized one of the blue plugs with red connector actually is from the A/C, pulled from the canister next to the motor mount.

Now I think I have a timing issue, but I haven't had a chance to trace it. The dizzy can only be in two positions, right?
 
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