Hey,
I was recently given a second cherokee with the crappy 2.8 v6 NP242 and an auto tranny. I know the 3.4 is a common swap into these to get a little more power but anyone know of other options. Also what tranny do I have in this think. I doesn't appear to be the AW4 that the 4.0's came with. Is this a GM transmission? Thanks.
I've covered this in plenty of detail elsewhere, so I'll just hit the highlights.
Easiest swap would be any other GM 60-degree V6 - RWD 3.1L or RWD 3.4L. The Goodwrench Service Replacement engine may also be used, but FWD has the starter mounted on the wrong side.
The OEM transmission is the "Baby 904" - the Chrysler A904 with a Chevvy bellhousing pattern. May as well replace it as well - the THM700R4 will give you a reasonably solid transmission (1988-up THM700R4/4L60. Avoid the 4L60E - additional electronics involve) as well as an overdrive gear. The THM700R4 can usually be found in the S-series pickup/Blazer, and you can also find a 4WD version in the K-1500 (although you'll probably have to swap bellhousings.)
In 4WD trim, you can usually find the NP231C behind the THM700R4/4L60 - which has a slightly wider chain, I believe, than the NP231J.
AMC was fairly well-known for using GM engines when they needed something they weren't making (two Buick engines, a Pontiac, and a Chevvy,) and a lot of Chrysler transmissions (A727, A998/999, A904) - although there were a lot of "early" AMC vehicles with Borg-Warner slushboxes, and they also used the THM400 in Quadra-Track vehicles in the early 1970's.
Anyhow, the RWD V6-60 would be the easiest swap. Next easiest would be the V6-90 (231, 262ci)/Small Block Chevvy (273-400ci,) since both use the same mount cradle, and an adapter cradle is available from Advance Adapters. Since these use the "GM V8" bellhousing pattern, you have more to choose from - you can use the THM350 or THM400 (heavy-duty three-speeds,) the THM700R4 w/SBC bellhousing (native in K10/K1500 pickup and Suburban,) and even the earlier versions of the 3L80/4L80 (the 3L80 is the later name for the THM400. The 4L80 is a THM400 + OD. NB: Neither than THM350 nor the THM400 had an overdrive range - but they were
rock solid slushboxes.)
The 242ci AMC six can be jammed into the engine bay, but recall that the front clip was redesigned for the 1987 model year to accommodate the much longer inline six engine. Pity they're going away from it - if the I6 is such a bad idea, why have BMW and MBZ been using it for the last forty-plus years, and why is Chevvy bringing it back in Vortec trim? I keep waiting for Ford to bring back the Cleveland Six (240/300ci, used in light trucks) as well. I think Dr. Z cancelling the tooling on the 242 was an early sign of senile dementia, y'ask me...
The NP242/AW4 swap
can be done, and I think there are a few here who have done it (old_man comes to mind - you may want to try to PM him,) but you'll need to make sure your fab skills are up to scratch before you even start that job...
