1986 Comanche 2.8L V6 Question

[86 comanche]

so that is what i got... i was looking to see if anyone knew of ne thing that will normally goes wrong with them... it has 175k mi on it and it is still going strong just did fluids and filters for it and ive been putting 91octane and injector cleaner in it and that has been helping... or at least i think it has been... and any one know about the tranny... i think it is 3spd with OD... but i have found out that if i keep it around 55 on he freeway i get decent gas millage... i know that is cuz of the gear ratio in the rear end(dose anyone happen to know what that is by the way??)... and what ratio should i get that is more of a high way gears so i could do like 65-70 and still get decent gas... and the truck has a 3" lift in the front but the back is stock so it looks like it is leveled out... it is my new project... i want to do a 4.0L swap out of a Cherokee but i want a F.I. engine so i get better gas millage and i dont have to worry about hills... but that is going to be a future project when i have money... this is a daily driver... just tell me what you think... and any thing that you know goes bad on them or things that i might need to worry about with it being a daily driver... and if anyone has any free parts or cheap parts that you think i could use just tell me and ill think about it...

Thanks for the help in advance
KC

[hondastomper]

IIRC, that 2.8 is a GM engine. My dad had one in an S-10 and it was always having problems. I don't think a 4.0 swaps in easy...from what i've read, people swap in a 3.4 V6 from a camero or something cuz it bolts in easy

[weasel_ugs]

That 2.8l is severly underpowered, I put a 3.4l HO GM crate motor in mine and is much better, and its a direct bolt in all you need is an electric fuel pump:fashizzle:.As for fuel mileage it isnt the best I got maybe 14 MPG from mine in a 5spd. You probably have 4.10 gears like mine does. Don

[86 comanche]

i just thought that maby the 4.0 swap would be easy cuz i thought that the frame was the same... but i guess scratch that... i know it is underpowered but i just figured it was old... guess not... if it is a gm motor i wonder how the 4.3L out of the s-10 would fit... i had one in my old s-10 and it was a beast... but that would take a lot of fab. work... well weasel what dose that 3.4 come in that i could get from a junk yard so i can go take a look a it and get prices on a junker and rebuild it...

Thanks for the advice...
Keep it comming

[AZXJ]

4.0L wont fit the 2.8L MJ because the fire wall isn't setup for the longer 4.0L. 3.4L or 4.3L would be much better swaps for this jeep. There should be a tag on the diff listing the gear ratio.. Watch for overheating, the 2.8L is known to eat head gaskets, and have poor oiling..

Take care
Dave

[86 comanche]

i dont know... so far it just hangs out just a lil over the blue area and the oil pressure stays at about 40 but i know that cuz its old when it gets hotter out it will too... bu ill keep a close eye on it

[jporvaz]

I bought an 85 XJ off a guy a year ago. It had 190k on it. It was stock. The engine was 2.8 V6 and the gears were a 3.73. In 85, the 3.73 was used if the rig had a towing package. If it has the "off-road" package it could have 4.10s. It's possible to have 3.31s if it has the fuel economy package. I've had to replace the radiator because it was clogged. I overheated at freeway speeds. Since replacing the radiator, I've had no problems overheating. If you have a 3spd tranny, no OD, it's probably a TF904. In the past year, I've not had any major malfunctions and I wheel it on a regular basis. It is not a DD, however.

A 4.0 swap is easy, nor is it recommended. Too much fabrication is necessary. The popular swap is the 3.4 because it bolts right in. You can also put FI on it.

I've got a book full of articles on XJ/MJs that I've put together since I got mine, if you're interested in looking through it. I've also got several links to various internet sites on XJ info.

[86 comanche]

i am not sure what sort of package it has... it dosnt have a toe hitch but i think it is a long bed if they made them... it looks longer than a normal bed... i would definitely like to take a look a that book sometime... if u could send me a few good links that would be appreciated too... is the xj/mj the same thing except for the bed/suv body on them??

[weasel_ugs]

The 3.4l I bought was a direct replacement for 82-85 S-10's so Im not sure if there is a 3.4 in something else that would fit(intake might be different for FI).
High mileage 2.8l are even worse on power, they wear out pretty fast. Mine is an 86 longbed so yes they did make them. Don


As for the 4.3l swap the trans is a different bolt pattern so that has to change too, I originally looked at a 4.3l swap but decided it was too much work considering I needed to fix it quick to drive it to work.

[86 comanche]

yea i will prob go the same rout you did cuz i need to keep it on the road... how much was your engine?? i know it will be diffrent if i get a junker but it will give me an idea... do you have a write up/pics of your swap... dose everything just bolt up for the most part?? is it just like a weekend job??

[jporvaz]

Off-Road Adventures (oramagazine.com) did a 4 part series on the XJs earlier this year. Most of the articles were about upgrading for off-roading but had info on the base package.
www.off-road.com/jeep/cherokee/xjtech/engine/28-34swap.html is a write up on an engine swap.
www.jeeptech.com/engine/gm173.html has basic info on the 2.8 engine.
www.amcyclopedia.org has a bunch on info on various aspects of the 2.8 jeep
www.4x4wire.com/tech/60degreeV6/ is an article about increasing the power of the 2.8
www.jeephorizons.com/tech/xjstockspecs.html- has all the stock spec info

My "book" has reprints of all these webpages, and then just stuff that I've researched primarily for beefing it up for crawling, not DD

I work at Phx College if you want to try and get together sometime. Work hours are Wed-Sat 0500-1500.

[weasel_ugs]

Thanks for the links but now Im a bit worried.Originally I had the engine in my XJ with a manual trans with no wierd vibrations so I thought nothing about an external balanced engine, now its in my MJ with an auto and the first article mentioned needing to balance the flexplate:aagh:.( I havent run the engine yet in the MJ).
I will say the power the 3.4 has was comparable with the 4.0 in my 92XJ. I paid $1700 for a new crate motor using my discount(wholesale price to my dealership) but that was at least 8 yrs ago.the article mentioned he paid $1700 too so either they came down in price or he got a discount also.Even at that price I wasnt sorry I did the upgrade. Don


Off-Road Adventures (oramagazine.com) did a 4 part series on the XJs earlier this year. Most of the articles were about upgrading for off-roading but had info on the base package.
www.off-road.com/jeep/cherokee/xjtech/engine/28-34swap.html is a write up on an engine swap.
www.jeeptech.com/engine/gm173.html has basic info on the 2.8 engine.
www.amcyclopedia.org has a bunch on info on various aspects of the 2.8 jeep
www.4x4wire.com/tech/60degreeV6/ is an article about increasing the power of the 2.8
www.jeephorizons.com/tech/xjstockspecs.html- has all the stock spec info

My "book" has reprints of all these webpages, and then just stuff that I've researched primarily for beefing it up for crawling, not DD

I work at Phx College if you want to try and get together sometime. Work hours are Wed-Sat 0500-1500.

[mudog715]

yea i will prob go the same rout you did cuz i need to keep it on the road... how much was your engine?? i know it will be diffrent if i get a junker but it will give me an idea... do you have a write up/pics of your swap... dose everything just bolt up for the most part?? is it just like a weekend job??

About 10 years ago I helped a buddy swap a 3.4L in place of his worn out 2.8L in an XJ. Mechanically it was pretty much a bolt on and he installed the long block with the 2.8L carb and drove it to my place. My job was to pull the carb and convert it to OE GM TBI fuel injection. The 3.4L was never used in trucks and therefore no OE TBI systems exist for it. The car applications were all MFI and most were front drive, which will not fit in a rear drive application. I believe the only rear drive 3.4L were in F cars (camaro/firebird). Anyway I made it work, and work well. We used the computer and harness from a S10 2.8L TBI setup, a Holley 2.8L TBI intake and Holley 2BBL TBI unit intended for a 4.3L. The combination of the 2.8L ecu and 4.3L throttlebody worked out well. It would run a little rich for the first 100 miles or so until the computer trimmed it back and it was close enough it never threw a code doing so. I still have the wiring diagrams around here somewhere.

Power-wise, it ran dead even with a 1995 4.0L Cherokee although the new Cherokee was probably 300# heavier. Fuel economy was much improved over the 2.8L, although still not great because of the lack of overdrive.

[86 comanche]

thanks for the info and every thing... when i go to do this(when i get money) it is good to know that there are ppl out there that can help me out some... if anyone else has any info or some kind of a parts list that i would need so i can get a idea of the things that i am going to have to get made or find some where