87 YJ 4.2 -> 4.0 swap questions

also - one more question - the suspension on my YJ is pretty well shot as well - esp the front leafs which are bent with frozen bushings - can one use the front springs from a cherokee on a YJ? how about the rear ones? thanks. bennett

You will need a fuel tank with the electric FI fuel pump in it, or an equivalent external pump. External pumps are problematical, because the suction side typically doesn't work right and is very very sensitive to leaks. You will need some way to fit a crank position sensor. Advance Adapters has a bell housing for this purpose, but I don't know how many models are available or whether there is an AT version. There is also a crank pulley CPS adapter available.

Your transfer case input shaft spline count and depth will be different from what the Cherokee AT uses. The quickest way to solve this problem is to change the TC input shaft, which requires disassembly of your TC. Don't know about the drive shaft, but I'll bet the AT from the Cherokee is longer than what you have now.

Earle

I hear that you can't fit the transfer case with full time 4 wheel drive into a wrangler. I forget the exact name, is it Selectrac?

Troy

thanks earl - a few questions then: can i take the fuel pump out of the cherokee and install it into the YJ? and what if i was to swap out my entire engine/TC/trans with the one from the cherokee? wouldnt that eliminate the need for installing a CPS and the adapter plate? i suppose i'd need a different driveshaft... and perhaps front drive shaft? and the springs? thanks for your help... bennett

The full time is Quadratrack. It has only 4hi-N-4lo

The fuel tanks are different, so you can't put the pump from the Cherokee in the Wrangler tank. Now I don't know whether the Cherokee tank fits in the Wrangler, but I do know that you need an FI tank to make the 4.0 work. An external aftermarket pump will "work", but as I pointed out they are problematical.

Before thinking about swapping the entire drive train, you'd better get out a tape measure and see what is what. The Wrangler drive shaft is too short as it is, as people find out when they install lift kits. If the Cherokee engine mount to TC tail shaft distance is longer, then it won't fit. If it's a Selectrac, it "really" won't fit. I haven't made this measurement myself, but I am pretty sure that you will find out, that the Cherokee drive train is too long.

Wrangler springs from

are not too expensive. The stock springs on a Wrangler are pretty flat, so your existing springs may not be as bad as you think. The best way to get the old bushings out is with a gas wrench.

Earle

thanks all. Earl - can i ask you to clarify some things?

1st off - i am clueless as to the nature of the 'Selectrac' and 'Quadratrac' so what l do i need to look for to detemine their presence? 2nd - besides the driveshaft length - which is pretty obviously different i would imagine - can't i just swap my tired old Peugeut 5sp with the AT that comes with the Cherokee? since this is the tranny and TC that comes with the motor, it would thus eliminate any need for adapters for the CPS, as well as the problem of pilot bushing mismatch, and for finding a 4.0/5sp manual computer... isnt that right? all i would need would be a YJ driveshaft with the correct spline count yes? i assume my stock (5sp) shaft wont fit - correct? sorry for all the questions, trying to figure out if this is a good idea... cheers, bennett

The big problem you are going to have is that I am 98% sure that the AT you want to use is too long. If the Cherokee has a Selectrac, then the combination is definitely too long. Look at the 4wd shift knob on the Cherokee. If it has 2h-4h-n-2l like your Wrangler, then it is Commandtrac, which is the manual option. This means that the TC is not too long, but you still have to worry about the transmission. If it has something else that looks like full time four wheel drive, then it is Selectrac. The difference is that the Selectrac has an interaxle differential in it, which is real good for slick roads, but adds too much length to fit in a short wheelbase vehicle like the Wrangler.

What you need to do is first measure from the back face of the engine block, where it bolts to the transmission housing, to the back end of the transmission, where it bolts to the transmission case. If this dimension is longer on the Cherokee, then the transmission will not fit. Then make another measurement, to the end of the TC where the rear drive shaft sticks into it. It is important to realize that the rear drive shaft on the Wranglers cannot be any shorter than it is, without increasing the likelihood of problems such as vibration. People have installed longer transmission/transfer case options, but not without welding a custom driveshaft or resorting to expensive constant velocity joints or slip yoke eliminators, that seem like they would be way out of range of your budget.

The spline count I am talking about is on the shaft between the transmission and the TC. You would have to change this, if you decided that you could use the transmission but not the TC. As far as I know, the output splined shaft is likely to be the same. In other words, your existing drive shafts will work, but only if the transmission/TC combination is exactly the same length as what you have now. Otherwise, this is not a good idea for you.

You can get more information from the Advance Adapters Jeep Conversion Manual,

The Conversion Manual is $10, and theyhave gone to the trouble of measuring a number of different Jeeptransmissions and transmissions that might fit in Jeeps. Earle

The front springs on a Cherokee are Coil springs not leafs so unless you're ready to convert your YJ to a four link... no dice.

thanks alot - i get it now... i'll have to take a tape measure along to decide whether this is a good idea. i suppose $500 is reasonable for a low mileage 4.0 engine + computer etc etc - yes? in truth, this vehicle is my daily driver, but the motor is tired and the carb has given me nothing but trouble - if i cannot make a relatively cost effective engine swap i believe i will be selling it and buying an 80's Toyota 4runner or 4x4 truck. i had gotten pretty convinced that i just dont have the time, the money, the space, or the energy right now to make a proper vehicle out of this wrangler... but then this opportunity popped up and i figured i'd give it a shot... guess i'll just have to see. thanks for all the advice, bennett

Yes.

I paid almost $4,000 for a new 4.0 in my Cherokee, of course someone else did the work and they replaced a bunch of other stuff while it was apart.

Jeff DeWitt

bobv> thanks alot - i get it now... i'll have to take a tape measure along to

I paid $3,000 for a new 350 in my Suburban. That's more cubic inches than you got, and cheaper too. Always a good thing to remember, when dealing with Chrysler Products, is that you are going to pay more, just for the privilege of dealing with them. Too bad Chevy doesn't make a removable top short wheelbase 4x4.

Earle

AMEN to THAT! :)

b

That is a shitload of cash for a 1988 engine, plus a shitload of work...

If the reason the engine is available is accident related, you don't want it. Impacts on engines that old are usually bad news.

Why not just buy a new Weber carb or find an old mechanic that actually knows how to set a carb up?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

Yeah, but you have a soft block chebby motor, not that wonderful 4.0 six. Odds are my 4.0 will still be going strong when your ready for another rebuild.

I've got an unlimited warranty for 18,000 miles, (engine and labor if it fails), after that I have to pay for labor but the engine is warranted for as long as I own the Jeep... and I expect to have this Jeep for a LONG time.

More often that not you really do get what you pay for.

Jeff DeWitt

Earle Hort> I paid $3,000 for a new 350 in my Suburban. That's more cubic inches than

Afaik, the original engine in the Suburban did 260,000 miles. It was burning oil at a rate of a quart every 300 miles, and I had one inch aftermarket breathers in both valve covers, just to keep the blowby off the windshield. I have had the replacement engine for five years, 30,000 miles, so the warranty I got with it is pretty much moot now. I expect it will also last as long as your Jeep. ;^)

Earle

My original 4.0 had 300,000 miles when a rod bearing started knocking, still had lots of pep and never did burn any oil. I'm using better oil and being a lot better about oil changes with this engine so it ought to go even further. This is a quick little Jeep and I tend to drive it enthusiastically. (It also gives me a steady 20 MPG)

If we both keep coming back to this NG I guess we will find out which vehicle lasts the longest .

Jeff DeWitt

Earle Hort> Afaik, the original engine in the Suburban did 260,000 miles. It was