1985 jeep cherokee v6 automatic

[megabyte5689]

Why did these GM 2.8L V6's break down so soon?

 

[GSequoia]

I really thought the transfer case would of.
thats not good.

The NP207 may bolt up but the case isn't worth it, you'll kill it. You want an NP231 or 242.

Now here is the question? Why not run the donor vehicle's case? If it is because it's 2WD you've got another problem, the AW4 has a 2WD and 4WD version, the tail housings are different.

 

[GSequoia]

Why did these GM 2.8L V6's break down so soon?

The 1980s did not treat any of the Big Three well, particularly General Motors, they're still fighting the bad reputation they gained in the 70s and 80s.

 

[megabyte5689]

So why were these engines so crappy?

 

[techshooter02]

you are right the doner rig was a two wheel drive aw4, So i should be able to just change the rear tail housing from a bad aw4 out of a 4x4.

my other problem is that the 85 xj with the v6 has a three speed auto. I need to find out what the transfer case is the is attached to it. I'll look at it tomarow and see.

 

[jeepcomj]

you are right the doner rig was a two wheel drive aw4, So i should be able to just change the rear tail housing from a bad aw4 out of a 4x4.

my other problem is that the 85 xj with the v6 has a three speed auto. I need to find out what the transfer case is the is attached to it. I'll look at it tomarow and see.

*sigh*

no, you can't use that transmission without completely tearing it down. a 2wd transmission also has a different output shaft that will not spline into a transfercase, and it is too long for the 4wd tailshaft anyways.

so, your donor has just unbecome a donor.

the transfercase attached to it is an np207 if it's command trac, and an np228 or np229 if it is a selec-trac 4wd system.

all of these have 21 spline input shafts, and are also the long input shafts. the Aw4 uses a 23 spline short input shaft if it's newer than mid-1990. 1987-mid 1990 used 21 spline input on the Aw4 so the np207 may bolt up, or the np229 may bolt up.

the 3 speed trans is either a TF904 or a TH904 IIRC, and is a gm 60 degree v6. you won't be able to use this transmission.

so, the two main things you'll need to get are a good used aw4 4wd transmission, and transfercase. DO NOT buy the transmission unless it comes with it's associated torque converter...the torque converters wear in to the transmission and I do not advise swapping used torque converters between transmissions.

 

[jeepcomj]

So why were these engines so crappy?

poor powerband...no hp or torque, it was surpassed by the 2.5 4 cylinder.

heavy breakdown on parts...everything wore amazingly fast. my 86 comanche came with one and by 66,000 miles it was on it's second engine. i put 1000 miles on it and hated it, so i upgraded to a buick 3800...i had time, wiring know-how, and fab skills on my side though.

poor oiling due to small oil passeges and lack of extra ones.

it was choked (literally) by the 2barrel vacuum carbeurator (it's a POS that sucked the life hp and gas mileage from the 2.8, though it didn't have much regardless).


the 2.8 as a motor is just fine. for a small car like a fiero.

not for a 3,000 pound jeep.

 

[WB9YZU]

So why were these engines so crappy?

The truth of the matter is that they were not that bad.

For the time, the early 80's, about 90k was about as long as things lasted then it was junk and you threw it away.

The nations manufacturers were just converting to EFI, so carbs were still around.
The carbs that were around had extras like variable mixture, electric enrichment circuits, and vacuum secondarys that a lit of people didn't know how to deal with. (Tuning a carb was always more art than science anyway). The early 2.5L came with a carb and converted in 85 IIRC. The 2.8L never went EFI, probably because AMC had the 4.0L in the works.

Emissions equipment was becoming more complicated because of new EPA mandates and that made the plumbing on all engines, especially carburated models more complicated.

In retrospect, given the times, the 2.8L really wasn't that bad, it's just that the 4.0L is so much Better .

It could have been much worse, AMC could have bought the engine GM put in VEGAs or the first GM Deisels (that were based on a 350) -LOL!

 

[techshooter02]

well nothing like having some nondoner stuff around.
we might just go extream with this one and make a v8 crawler out of this one. just need to have a bigger shop...LOL

 

[techshooter02]

anyone have any sites they know of where they did the v8 conversion??