998 to AW4 swap

[doc65]

Ok, so I did a search & read all the threads that came up, but didn't really find what I was looking for.  Has anyone actually installed an AW4 behind a 4.0/4,2 in an eagle?  I know about driveshaft lengths, longer in front & sorter in back, and that I'll need the trans controller, also  possible shifter issues. I can easilly deal with all those, my main concern is really the trans tunnel & how much if any floor pan mods are needed, secondarily would be the cross member, weree you able to make the stock work in any way, but ultimately I can build a replacement for that if I need to.

Just figure I'll see if it's really been done vs just imagined/planned

Thanks
Doc

[carnuck]

It's smaller diameter than the 998 or 727. I have an AW4 with NP208 if anyone needs measurements.

[captspillane]

I've got one from a rolled Cherokee I parted out. Its destined to be installed in a Eagle Station Wagon. The body is longer but obviously smaller diameter than a 998. It should fit without a problem.

I plan on using an Eagle transmission crossmember with holes drilled to mount an original Cherokee AW4 transmission mount. Its the same way I plan on installing the AX15 and other transmissions. The crossmember will be the original Eagle unit, but it will no longer use the original studs. The subframe continues straight back for at least 8 inches, however, so I expect to line the crossmember up laterally and pinch it against the subframe with a jack with the transmission bolted to the engine. I'll drill four half inch grade 8 bolts through the entire subframe. The head of the bolt and the washer will be inside the car under the carpet. I will put a nut and washer to tighten the bolt against the subframe so that it will not spin. A second lock nut will tighten the crossmember against the first nut. There will be a space the thickness of the first nut between the subframe and the crossmember.

I plan on using the XJ transmission shifter. Its a cable unit so I can line it up where I want it in the cab. I will still need to cut a hole because the shifter was recessed through the sheet metal.

For driveshafts, I will be using a slip yoke NP242. On my SX4 I've had a slip yoke driveshaft for several years. I put a piece of metal pipe about 3 1/8" long inside the driveshaft's slip yoke to disable it and then connected the XJ slip yoke right to the original U joint. The balance of the drivehsaft was not affected enough to make a noticeable vibration. For the AW4, because it is about 3.5 inches longer, I expect to use the original driveshaft without any modifications.

With the axle fully pressed down against the spring stops the slip yoke at the transfer case and the slip yoke in the driveshaft will take up the difference in length of the transmisson. Fully extended there will not be enough travel for the driveshaft to pop out of the back of the transfer case. With my SX4 and its original short transmission I needed that 3 inch pipe spacer to keep that from happening.

In the front the driveshaft slip yoke only needs to travel about an 1/8 of an inch to compensate for vibrations because the front axle is bolted to the engine which is bolted to the transmission and so forth. The front slip yoke, however, has about three inches of travel available. I suspect that the original driveshaft might actually be long enough to work. If its not long enough, I was going to try adding an XJ cardigan u joint to extend the driveshaft. Either way I hope to make the original driveshafts work without any welding or custom work.

[doc65]

Well looking under the wagon last night at the stock setup, if the aw4 really is 3.5" longer (ish) it's going to hit the floor boards & a brace that runs across the trans tunnel.  You might get away with an inch, but otherwise the T-Case is gonna hit.  That hump that's raised for T-case clearance is not a small thing either.  I MAY need to rethink this, making it run is one thing(i've done it in a ZJ and hooking up the TCM isn't really a big thing), that much masageing of the cars floor pan, well I'd like to avoid it. 

[carnuck]

Did that account for the tcase length? I was thinking an NP208 (since it's shorter) with the AW4. Trans crossbar would be hard for me since I don't have a shop anymore (no welder either)

[doc65]

Carnuck,

I wasn't aware of the NP t-cases being different lengths, at least not in the dimension I'm concerned with.  The only one I see as being difficult is the mounting surface with the trans to the major portion of the rear face, specifically the rear face of the drop area, that's what's gonna hit as far as I'm concerned(on my wagon that is), the SX4 is a stick and will stay a 5 speed stick, the measurements I have is that the AX15 & NV3550 are both 5/8"(if memory serves) longer than the T5, that much I can get away with...

Doc 

[carnuck]

This thread was about the automatics. No wonder we're confused! LOL!

[doc65]

Yeah, it's the auto that I'm concerned with.  I REALLY want an OD trans, and I've owned a few AW4's, I know it will bolt up with little to no issue, the clearance with the trans tunnel & floor boards is my only real concern.  The OTHER car, which is a manual, should be a NON issue as the length of the stock trans & anything I'd use as a replacement is so close.

I won't know till I get closer to it with the seats & carpet out, but I envision being able to take a rectangle out of the floorboard that includes the rear of the T-Case hump, move it back about 4", then bake a patch to fill the hole left by lengthening the tcase clearance hump.  Sounds like a job for the plasma cutter.

[captspillane]

My measurements of my NV3550 and NSG370 were both 24" from bell housing mounting surface to transfer case mounting surface. For the T5 I got 6 5/8" for the bellhousing and 15 1/8" for the trans, so 21 3/4" total. Thats a difference of 2 1/4".

The TF998 I had 22 3/8" and the TF727 I had 22 1/2". I haven't measured my AW4 yet.

[doc65]

I don't remember where I got the 5/8" figure, you might be right, I can verify the AX15 at 24" as I have one sitting out right now, also the 42RE used in the ZJ grand cherokee is approx 26 1/4", go that sitting out as well, the AW4 I'd have to crawl under something to measure, so it'll wait a little.

[captspillane]

Oh wow, I planned on replacing the drivetrain in my 06 Rubicon with something stronger and putting that 42RE in an Eagle SW. Thanks for taking that measurement. I didn't realize it was that much longer than a TF998.

[carnuck]

42RE is also notoriously weaker than the AW4 and eats more gas due to high friction and mass. When the '93 Grand Cherokee went from AW4 to 42RE, they lost 4-5 mpg!