Manual UPGRADE. Swapping out the BA10.

I found a nice Comanche for sale locally through this guy I've known for the last year or so. He put 285K on a BA10 before it finally died. Well he sold this Comanche to me for $800; Dad and I are planning on swapping in a new transmission of some sort.

I have a T167/T150 bellhousing for a 4.2L Jeep that will allow for a NP435 to be swapped in from a Ford pickup. I can get any manual transmission from the local PullaPart for about $60 with core and warranty included. I want to hear from anyone who knows anything about the subject of upgrading a transmission as to what transmission is the best. My thoughts were SM420, SM465, NP435, T18, or T19, while leaning toward the NP435.

I would like to choose one that is easily found and will still be kicking hard after many thousands of miles have been put on it.

We have access to just about any fabrication or machining tool needed so modifying a bellhousing isn't a question. We will have to adapt the bellhousing to accept the CPS anyhow. I want THE best transmission in there to provide great strength and if possible have an overdrive gear.



It feels like I have rambled plenty, and YES I have checked out Novak and their plethora of info, but I decided I ought to check here as well.


Lets hear what you've done/know.

NV 4500. None of the old 4 spds you mentioned have an overdrive.

I use the BA-10-5 bellhousing in mine with an AA adapter plate. Simple swap, and I like the internal slave as it leaves more room for a front driveshaft to cycle.

Are you planning on really flogging this thing, or what?

For most uses, an AX-15 or an NV3550 should be plenty - and both are readily available with AMC bellhousings, saving you conversion woes. And, they fit in the transmission tunnel - while you'd have to modify it to fit some of the larger gearboxes (NV4500, NV5600, SM4xx, some of the old NP four-speeds, ...)

Yah, the AX-15 isn't as tough as the rest of these, and the NV3550 is close, and neither has a really good "granny gear" - but how much do you really need it? And, since you know you're going to do it as a conversion anyhow, you can take your time and overhaul the gearbox before you throw it in in the first place.

There are some old NP four-speeds that have OD (I think Dodge used them,) but they're uncommon. I wouldn't look for them too hard at the moment.

If you're set on using an older iron four-speed, plan on throwing in a Saturn or a Klune between the transmission and transfer case to gain an overdrive (you'll effectively be splitting all of your gears - turning your four-speed into an eight-speed. But, what the Hell, right? It's the same thing the High/Low range selection on your transfer case does - so you're just doubling it again. Same way the large farm tractors work - four- or five-speed transmission, three- or four-way gear splitter. Things don't usually have the ability to go faster than 25mph, but they'll pull a mountain behind them doing it.)

And, if you're set on hauling, ditch the 3.07 gearing in the axles - go to a 3.73 or 4.10, and you'll be happier. The 3.07 gearing used with the manuals was a mistake, and I honestly don't know why AMC did it.

@CRASH - why do you say the internal slave allows for more front D/S articulation? I haven't taken an accurate measurement yet, but the bellhousing on the 1990 and 1994 AX-15s I have look to be about the same, so that shouldn't change the length/operating angles of the front D/S, unless I'm missing something. And, that damned internal slave kept popping on me (I went through four gearboxes and six slaves over the space of a few years,) so I'm going to end up putting the 1990 (small pilot) input shaft in the 1994 (external slave) transmission, overhaul the transmission, and put that in. That saves me having to keep track of the pilot bushing - which is the sort of detail I'm likely to forget. Do you see any problem with that, or does it seem sound to you?

Oh - and how's the kid? Apart, of course, from keeping you busier than a one-armed paperhanger with hives...

It's a matter of where the Atlas output sits in relation to the external slave and the D-44 front's pinion. The driver's side external slave is in the way, at least on the aftermarket NV-4500 bellhousings.

The Ford T-19OD is the four speed that had an OD. Ford, ever clever, switched the position of third and fourth gears, and then swapped the third gear sprags from counter shaft to input shaft. Get it? Still only had a 4 to 1 first gear, though. Gear spacing is WIDE as you may imagine, and suited to big blocks and diesels more than the little old 4.0.