View Full Version : Some ??'s about gearing in our new MJ

March 26th, 2005, 10:06
Ok, so we finally got the new MJ on a lift to see what we actually wound up with and got it out for a few test runs. First off here's what we do know:
-1989 MJ Pioneer
-D30/D35 unknown gears but high, I'm guessing 3.23's maybe
-4.0 Renix
-Some kind of T-flite trans (904/909/999 anyone know how to tell the difference?)
-NP207 t-case.
-235/75R15 BFG A/T's
-6.5' Meyer plow
-Air bags in front suspension
-factory aux fan and a large tranny cooler
Initial test drives indicate a pretty good working tight rig. The first test of the 4wd (without the plow on) resulted in some nasty noises from underneath, however this was a driveshaft to exhaust clearance issue that was quickly eliminated by letting some air out of the bags.
The truck drives well on the road with the high gears somewhat making up for the lack of an overdrive. We had the chance to get it into some deep mud and snow last night and it is defineately begging for more gear, not terrible but nowhere near our 4.0/aw4/242/3.55 and worlds away from the 4.0/aw4/231/4.10. I'd like to keep the axle ratio's the same for now to keep the revs in check on the road with the t-flite. What I'm wondering is if I would see a noticeable difference in 4-lo if I swapped in a 231 (2.72 low) in place of the 207 (2.61 low) or should I just bite the bullet now and swap in the aw4/231 and 4.10's( this is the eventual plan but I'd like to run this gear in the rig it's in for one more season). Will a 23 spline 231 bolt off an aw4 bolt up to the torque-flite and will the 207 bolt to the aw4? How much power loss would I notice in 4-lo in my '91 4.0/aw4/4.10 with the 207?

BTW nobody needs to tell me that this truck should not have a t-flite or a 207 I already knew that of course but it does so that's what I have to work with and any hints or tips about them are appreciated. Also I already have a spare 207 out of an '87 XJ and since I was a dodge guy before a Jeep guy I've got access to lots of spare t-flites.

March 26th, 2005, 11:08
Run fast away from the 207 T-case. WEAK.