2.8 --> 3.4 questions

[MJ300]

I'm planning on swapping in a 3.4 for the 2.hate in an 86 MJ and want to make it a nice offroad truck. It's currently only 2 wheel drive and was wondering what transfer case would I'd have to get? The truck has an auto in it.

 

Another question....I'd love to do the 97+ conversion as well (i.e. - interior, dash, header, fenders, etc.). But the more I thought about it I don't think I could make the interior 97+ because of the fact it's gonna be a 3.4 and not a 4.0. Won't the heater controls, vents, and gauges all be different or would it still be possible somehow?

[JeepcoMJ]

97+ is out the door unless you want to eliminate half the 97+ harness, use all the 97+ heaterbox and radio wiring (plus heater box itself), and do custom gauges and custom wiring to keep your 3.4 running.

 

 

I have to do all that to make the 86 that I have work...but I put a 3800 v6 in it (not bolt in).

 

 

to do the 3.4 swap, you use all the manifolds and other bolt-ons from the 2.8l to keep it carb'd (not advised), or you use just the exhaust manifolds and oil pan from the 2.8, and piggy back the 3.4 EFI harness to your factory harness with a 4.0 fuel pump in your gas tank.

[mvusse]

You can not bolt a transfer case onto a 2wd transmission without changing the transmission output shaft and housing. It would be easiest to find a 4wd 2.5 4 cylinder or 2.8 V6 Cherokee 84 through 86 (possibly 90?) to use for parts. That way you have everything needed, including all the little detail parts, with the exception of the rear drive shaft. For that you'd probably need to have your 2wd shaft shortened.

[Pete M]

you've got a tricky rig there. the only 4wd trans from a Jeep that'll easily work is from an 84-86 auto MJ/XJ. but if you bought a donor rig from that era, you'd be missing an opportunity to upgrade from the weak crap used in the early Jeeps. The front driveshaft was puny and the t-case was the less desirable NP-207.

 

What gear ratio if in your rear axle?

[MJ300]

I would imagine that they would be either 3.55's or 4.10's. This is sounding more and more like a pain in the butt with the limited number of things that will work such as the driveshaft and the old and weak transfer cases. :roll:

 

Think it would be a better idea to do the engine swap, spruce the truck up a bit and sell it for a profit? Only bought it for $350 with a straight, rust free body. Then look for a 87-92 so that I can fit a 4.0 in, and then do the 97+ stuff?

[Pete M]

It's not hard, you just have to pay attention to the details so you get the best of the best when you're finished. :D It'd be the same with any year Jeep. If you buy a 2.5L/5spd XJ 87-99, you'll get your front driveshaft, t-case, and front/rear 4.10 axles. then you just need the older 4wd auto trans (87+ are computer controlled).

 

the only "hard" to find item will be the trans, but car-part.com can help with that. :thumbsup:

[MJ300]

Alright, I've done a bit more research and I've found that the np207 and np228/229 are not the greatest or most reliable TC out there. I've also read that I could run an np231 or 242 out of an early cherokee that has 21 splines??? :idea: Is this possible? What tranny would I need to make this happen that would work with the 3.4L.....if there is any. :roll:

[JeepcoMJ]

Alright, I've done a bit more research and I've found that the np207 and np228/229 are not the greatest or most reliable TC out there. I've also read that I could run an np231 or 242 out of an early cherokee that has 21 splines??? :idea: Is this possible? What tranny would I need to make this happen that would work with the 3.4L.....if there is any. :roll:

 

correct. you need a 21 spline np231 or np242 with a long input shaft. they are out there, and not that hard to find.

 

your transmission is a torqueflite 904 (TF904 or TH904). you are limited to 86+ 2.5 or 2.8 liter comanches, or an 86 or 88.5+ cherokee 2.5 or 2.8l, or any 2.5l jeep wrangler YJ.

 

 

you CANNOT use an 84-85 cherokee TF904 without machine work. they were carburated, and thus don't have a boss machined to mount the crankshaft position sensor on the bellhousing.

 

 

keep in mind that torque converters also changed with the years, respectively, so do your research on part numbers to verify that the year of transmission you get has the same torque converter. the shift points between all of them are the same, but the bolt locations are different and therefore if you get the incorrect torque converter, it will not bolt to your flex plate.

That said, you can keep your torque converter and use it with the "new" transmission.

 

None of this is a big deal...you're not looking for a needle in a haystack, so don't sweat it.

 

 

I will advise you that if you do do a 3.4 conversion and decide to do the fuel injected upgrade, make sure that you get a 3.4 and the wiring for it from a 91-95 camaro or firebird that came equipped with a 5 speed. your transmission is shifted mechanically, with no electronic controller...you don't want to deal with the hassle of making a 3.4 auto ECU think it still has it's stock auto trans.