drive-and powertrain recommendations for full build

[jamespwsullivan]

I've had my 87 MJ for a little over 2 years.  What was going to be a "simple" upgrade of the rear axle to a Dana 44 (to  get me to the Metric Tonne place) has gone totally out of control. The rear is now a Dana 60 and the front a Dana 44.  Both geared to 4.56 with a four-link in the front, Hell Creek springs in the rear.  The lift is designed for me to be able to run 35s.  The original 4.0 l-6 has about 275,000 miles on it and the tranny is the much-loathed 5-speed.

I also have an XJ with around the same miles, so I am a fan of the 4.0 I-6 motor.  I have found an engine rebuilder locally with a good reputation, and I have also talked with HotWire about a harness, so what's the next step? It's a little weird that I don't do a lot of wheeling, but  am building the truck for some travelling I do on some pretty nasty fire roads and often just pairs of ruts that go from A to B.

I want to go to an automatic transmission and since I'm already committed to some new drive shafts and want a new motor (which i can spec for any year that will physically fit), I'm looking for recommendations for a particular tranny (with overdrive), transfer case and motor combo and from what years in particular.  If you have donor vehicle recommendations, that would be great.

i have looked over the forums using some generic search terms, and I apologize in advance if there's something out there with good info that I've missed.  Most of the posts I;ve seen so far seem to be focused on swaps that allow the use of existing wiring (with modifications) and sticking with MJ / XJ parts from a similar era.  (I do have a line on a very low mileage 4.0 from 2002 that I can use as a back up instead of gong straight to the reman.) Unfortunately my job keeps me hopping about 60 hours a week and it' tough to check out the forums on a frequent basis.  (yeah, I know... wha, wah, wah!)

Any thoughts you have are welcome.

[yxmj]

??? what is a "much-loathed 5 speed" ???

Never heard of one  :dunno:  a BA??

[jamespwsullivan]

Yeah.  I meant the Peugeot BA-10/5.  I described it that way because everytng I have ever read or heard about it is that it isn't worth rebuildng or replacing if there is another option.  To be fair, this tranny has the same mileage as the motor, and that's not half bad.

[Marine1Texas]

BA-10/5 gets a bad rap that is for sure. However I have one that has 284k on it, and it shifts and runs just fine. We took it out on my 2nd mj when we put in the new 4.6 stroker. It was in a truck that just went from going to the market and light light stuff around northern Texas Highway. However it is a light trans compared to the ax15. It all comes down to how it is used and treated. Most jeepers who off road will tear one up in no time.

[benjy_26]

I don't like automatics on vehicles that will often be used in austere conditions. If it were me, I'd do an AX15 swap and build the engine to basically stock spec.

[Blue XJ]

a 4.7 stroker and an ax15 are a fun way to go.  I originally had the motor with an AW4 and switched it to an AX15.   Ton's of fun to drive and plenty of power with 4.56's and 35's.