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Top 11 Transmissions And Transfercase Swaps - Happy Rowing

Pete Trasborg
| Brand Manager, Jp
Posted April 1, 2009
Photographers: Jp Archives

Top 11 Transmission And T-Case Swaps

Many people think the editors can get anything they want thanks to simply working for the magazine. The fact of the matter is that we have a ton of projects going and many of them you don't even read about in these pages. We are out there swapping parts, scrounging junkyards, combing online ads, and bribing friends just like you guys are. Heck, we are even on our backs in our driveways to do most of our swaps like you guys are. The difference for us is we've been doing this for a combined total of more than 50 years, and we've built and beat more Jeeps than many people have ever owned.

The point is, by being paid in peanuts for so long with so many projects we've gotten rather adept at saving money when swapping parts into our Jeeps. In this article we are going to look at swaps into Jeeps with Jeep engines. If you've swapped in another engine, the pros and cons of each component are still applicable. So, without further ado, here are our 11 favorite junkyard transmission and transfer case swaps to make your Jeep perform better, last longer, and still get you home from the trails.


Aisin AX-15
Donor Vehicle(s): Behind the six-cylinder in '89-'99 XJ, MJ, YJ, TJ and the '93 ZJSwap into: Any pre-'89 ('86 and earlier CJs will need an adapter or T-case swap) Jeep with the inline-six, but especially the '87-'89 YJ, XJ and MJ with the BA10/5 Peugeot transmission (might need to change the T-case input gear to 23-spline). It is also a good swap into '87-'03 four-cylinder Wranglers using Advance Adapters kit (PN 712563 (external hydraulic) or PN 712564 (internal hydraulic).

Identify: 16 1/2-inch-long case, 23-spline output, five forward gears, thick aluminum mid-plate which the front and rear halves of the case bolt through

Gears: 3.83, 2.33, 1.44, 1.00, 0.79 (First through Fifth); 4.22:1 Reverse

Pros: Good all around Overdrive transmission that shifts nicely, quiet, and is relatively lightweight.

Cons: Not a very low First gear and the unit has only marginal strength for V-8 swaps.

Comments: This is the Rodney Dangerfield of Jeep transmissions in that it gets no respect. With a mediocre First gear, the rock crawlers aren't tripping over themselves for it, and with enough strength for a six-cylinder, but likely not enough for a healthy V-8 the mud guys don't want it either. That said, it is likely the most common manual transmission in Jeeps still on the road. The '93 and earlier units got a goofy hydraulic throwout bearing which can prove problematic. The '94 and later units got an external slave setup. The later parts can be swapped to the early transmissions by using the bellhousing, input bearing retainer, clutch fork, throwout bearing and slave cylinder from the '94 and up unit.

New Venture NVG3550
Donor Vehicle(s): six-cylinder '00-'04 Jeep Wranglers and '00-'01 Jeep Cherokees

Swap Into: Any Jeep with up to 300hp, again with the 23-spline stipulation for the Peugeot-shod Jeeps, and the possibility of a transfer case adapter or swap for the '86 and earlier CJ's

Identify: Five-speed Overdrive transmission with composite shift tower, 16 3/4 -inch long case, and a 23-spline output.

Gears: 4.01, 2.33, 1.39, 1.00, 0.78 (First through Fifth); 3.57:1 Reverse

Pros: The most heavy-duty of the aluminum-case manual transmissions ever put in a Jeep; this transmission is also coveted for its lower First gear, and praised for its strength as evidenced by its OE installation behind small-block V-8s.

Cons: In a daily driver, especially one with the carpet-delete option, it is noticeably noisy at idle and lower road speeds. Also, it doesn't take normal gear oil, but special Syncromax oil which is more expensive and can be harder to find (read: you need to take more fluids with you on trail runs).

Comments: For its size and design it is one of the most heavy-duty transmissions you can score. For swapping into '93 and earlier Jeeps, be sure to grab the bellhousing and all associated clutch parts.


Advance Adapters
Paso Robles, CA 93446
Novak Conversions
Logan, UT 84321
Stak 4x4
El Paso, TX 79936
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