1998 TJ AX5 to AX15 Transmission Swap

In this thread I will chronicle my AX5 to AX15 transmission swap.

Background

Over the several months I've developed a problem shifting my transmission, an AX5 5-speed manual, into third gear. When I go to shift into third gear at speed (25+ mph) the transmission grinds before it will finally go in to gear. This problem is most likely attributable to a bad synchronizer. The only solutions to this problem are to either rebuild or replace the transmission. As the AX5 is a light weight transmission that is known to fail when backing a low output 2.5L with large tires, I see no point in spending money rebuilding this unit or replacing it with another AX5.

Now enter the AX15, the AX5's heavy-duty older brother. While the AX15 5-speed manual has similar gear ratios to the AX5 (1st and 5th are higher than the AX5, the rest of the gears are the same) and is similar to the AX5 in appearance, this transmission is known to hold up to the high torque I6 4.0 AMC engine and 5.7L Chevy V8's. Unlike the AX5, this transmission should be able to hold up to anything my puny 2.5L I4 can throw at it.

Parts

This swap required the following parts:

AX15 transmission- sourced from 1995 YJ Wrangler in Portland, OR
NP231J transfercase with 23 spline input shaft - sourced from 1995 YJ Wrangler in Portland, OR
1996-1998 2.5L Dodge Dakota Bellhousing - sourced from auto recycler in AR
Sachs Clutch Disk for 1984 Chevy Camero 2.5L - Rockauto.com
Timken Clutch Release (throwout) Bearing - Rockauto.com (made in USA!)
Pilot Bushing - Advance Adapters (made in SLO, CA!)
Transfercase Shifter Relocation Bracket - Advanced Adapters
Clutch tool - Advance Adapters
NP231J Slip Yoke Eliminator - Advance Adapter
Adjustable Upper Control Arms - Savvy Offroad (made in Tustin, CA!)
Rear CV driveline - still need to order, probably have built in Fresno or Modesto, CA
Front driveline - still need to order, either have new built or find one from a TJ or YJ Wrangler with stock AX15 transmission

Ughh, tranny build/rebuild......worst possible job......and to think, we call it fun.

Marconius wrote:Ughh, tranny build/rebuild......worst possible job......and to think, we call it fun.

Fortunately I don't have to open the transmission up, although I will be pulling apart the transfercase to replace the seals (make sure nothing will leak) and the output shaft (part of slip-yoke-eliminator install).

The bellhousing arrived from Little Rock, AR yesterday. Today I got it cleaned up and painted.

Damn. Looks good. You spray better than I do.

I've made a little progress since last posting:

The AX15 5-speed manual ready to go in.


The bellhousing bolted up


Side by side. The old AX5 in the back, the new AX15 in the front.



The AX15 secured to the transmission jack going in.


After bolting the bellhousing to the engine, I then installed the starter, which is secured by two external torx bolts (the singe most ridiculous fastener ever, had to buy a new socket set just for these two bolts).


Next I installed the clutch slave cylinder. The bellhousing did not come with the two threaded studs usually used to attach the slave cylinder, so I instead used two grade 8 bolts. When installing the slave cylinder it is essential to insure that the rod in the slave lines up with the cup on the clutch fork. Failure to align these can result in damaging the slave cylinder. Please forgive all the gauging from the transmission jack.


Once the transmission is in place, its time to install the transmission shifter. The method necessary for installing the shifter is insane and the engineer who designed it should be b*tch slapped. After fumbling around for a while I finally got the shifter installed.


Once the transmission was installed, the transfercase was slid into position using the transmission jack. Once the studs on the transfercase were aligned through the holes in the back of the transmission and the transmission output shaft was engaged with the transfercase input, the transmission was secured using grade 8 nuts.

If anyone is interested, I posted a far more thorough writeup on Jeep Forum:

Jeep Forum