tkgibbs27 Posted October 10, 2007 Share Posted October 10, 2007 Is it possible to swap the original engine, a GM 173 V6, with a AMC 258 I6 in a '86 Comanche? If so, would the transmission need to be replaced with a different one? And would I need to replace anything else? Link to comment Share on other sites More sharing options...
DirtyComanche Posted October 10, 2007 Share Posted October 10, 2007 Search for 2.8 to 4.0L swap... You'll find a bunch. I'm no expert on the subject, but you can't use the same transmission. And you'll need a 4.0L wiring harness. Along with the radiator, rad support and some other doo-hickies. Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 10, 2007 Author Share Posted October 10, 2007 Search for 2.8 to 4.0L swap... You'll find a bunch. I'm no expert on the subject, but you can't use the same transmission. And you'll need a 4.0L wiring harness. Along with the radiator, rad support and some other doo-hickies. well i see that i will more than likely have to pound in the firewall. Link to comment Share on other sites More sharing options...
Geonovast Posted October 10, 2007 Share Posted October 10, 2007 There's a couple other things to consider... Since they didn't put the 4.0 into the 86's, the firewall is different, and if yours is an earlier 86, you may have to modify your firewall. No, you won't be able to use your tranny, you'll need either an Ax-15, Ba 10/5, or Aw4. Yes, you'll need to replace the entire harness, engine bay and dash. New motor mounts, new exhaust. Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 10, 2007 Author Share Posted October 10, 2007 There's a couple other things to consider... Since they didn't put the 4.0 into the 86's, the firewall is different, and if yours is an earlier 86, you may have to modify your firewall. No, you won't be able to use your tranny, you'll need either an Ax-15, Ba 10/5, or Aw4. Yes, you'll need to replace the entire harness, engine bay and dash. New motor mounts, new exhaust. how do you tell if it's an earlier 86' model? Link to comment Share on other sites More sharing options...
Geonovast Posted October 10, 2007 Share Posted October 10, 2007 There should be a sticker on the inside of the drivers door, that will tell you the month of manufactur, I don't know the exact switchover time, but I'm guessing if it was made in 85 you'll need some modification. Link to comment Share on other sites More sharing options...
Pete M Posted October 10, 2007 Share Posted October 10, 2007 One last thing to consider, he's not asking about the 4.0, but a 258 and there's no way that I would trade one turd for another in any of my trucks. The 3.4L (from an early 90s Camaro or Firebird) swap is waaaay easier for the 86 trucks with the 2.8L and if you're up to the challenge, you can swap over the electronics and get the Camaro's fuel injection too. :D Link to comment Share on other sites More sharing options...
Geonovast Posted October 10, 2007 Share Posted October 10, 2007 I could have sworn I saw another post in here saying he meant the 4.0 instead of the 4.2... Well, yeah, a GM v6 would be a lot easier, Especially since you should be able to keep your tranny. If you decide not to use the 258(if you have one), I wouldn't mind snagging the Crankshaft. :brows: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 10, 2007 Share Posted October 10, 2007 the firewall changed to the 4.0 firewall in late 86 the early firewall is pretty much the same, just requires a bit of beating with a hammer on the lower right side, and lower left side, around the bellhousing area. so that won't be a problem. don't put a 258 in, they're crap. use a 258 crank in a 4.0 to get a 4.5 stroker tho!!!! and a 3.4 swap wouldn't be all that hard, I can get the wiring diagrams necessary for you to get it to run. I put a camaro 3800 motor in my 86 2.8 comanche, which is just 1 step higher, and also 1 step harder. Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 10, 2007 Author Share Posted October 10, 2007 is the 3.4 more fuel efficient? i am assuming it is more powrful. i don't know much about vehicles. my dad gave me the truck and said to swap the engine out because the 2.8 that's in it is a piece of crap, he left me to find out about what engine would be best. Link to comment Share on other sites More sharing options...
Pete M Posted October 10, 2007 Share Posted October 10, 2007 The 3.4 is a more modern version of the 2.8L. Swapping an entire drivetrain is not a good way to save money on fuel. Swapping an engine to gain more power and better reliability is certainly worthwhile. The simplest way is to just use the 3.4L block and put all of your 2.8L parts (intake, pullys, etc) on to it and then run a better carb. The more complex way is to swap the entire engien assembly including the wire in the harness from the Camaro and get the fuel injection system. I have no idea of your skills and determination so I can't say which is the better choice for you. See this site for some pointers: http://jeep.off-road.com/jeep/article/a ... ?id=277008 Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 10, 2007 Share Posted October 10, 2007 if you swap it, I highly suggest going with the 3.4 as it is an identical block, except it doesn't use a mechanical fuel pump so you'll have to get an electric fuel pump. then, you swap the oil pan, exhaust manifolds onto the 3.4 from the 2.8, so you can use the same exhaust that's on your truck now. the camaro wiring is easy....you just have to pull out the unnecessary wiring (lights, heaterbox, etc.) and lay it in as a second harness. remember that point...you are not replacing the jeep wiring harness, just running 2 at a time. by doing that, you now have a engine that operates off a seperate system than your 2.8. the engine computer is located in the righthand side of the engine compartment against the rear firewall, so that doesn't even have to go inside. if you do the 3.4 swap, ther is little to NO point in going back to the 2.8 intake system, as it sucks gas, and good carbs are hard to find, unless you buy the edelbrock 4bbl intake and a holley 4bbl 390cfm carb. that's $500 there, and in the end, you still have carbs. Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 10, 2007 Author Share Posted October 10, 2007 alright. so i'll get the 3.4L. what does it do for gas mileage? and will i be any good for off roadin' or does the engine really matter when it comes to that? i also need help with my gauges. my temperature gauge is incorrect it starts in the middle rather than where it should at the left. and my oil pressure gauge is pinned all the way to the right side. i can get it working sometimes but then it always ends up pinned back over to the right side after a little while of driving. i did a swap like this a couple of months ago: http://comancheclub.com/forums/viewtopic.php?t=4615 also when i engage it in to 4wd you hear this griding sound when shift gears. i don't have a clue what it is. Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 10, 2007 Author Share Posted October 10, 2007 I could have sworn I saw another post in here saying he meant the 4.0 instead of the 4.2... Well, yeah, a GM v6 would be a lot easier, Especially since you should be able to keep your tranny. If you decide not to use the 258(if you have one), I wouldn't mind snagging the Crankshaft. :brows: i don't have the 258, i was going to go pick one up at a wrecking yard. Link to comment Share on other sites More sharing options...
Eagle Posted October 10, 2007 Share Posted October 10, 2007 One last thing to consider, he's not asking about the 4.0, but a 258 and there's no way that I would trade one turd for another in any of my trucks. The 3.4L (from an early 90s Camaro or Firebird) swap is waaaay easier for the 86 trucks with the 2.8L and if you're up to the challenge, you can swap over the electronics and get the Camaro's fuel injection too. :D While I certainly don't agree that the 258 was a turd of an engine, I DO agree that a GM 3.4L V6 is a much easier and more logical swap for the 2.8L, since the block is the same and all the mechanical stuff is basically bolt-up. The GM injection and ECU can be run basically stand-alone and use the Jeep harness for the gauges and chassis. One consideration is that the 2.8L has an externally balanced crankshaft, meaning an eccentric weight in the flywheel (or flex plate). The 3.4L is "zero" or "neutral" balanced, meaning it doesn't have the eccentric weight. I believe you have to use the Jeep flywheel, so it'll have to be rebalanced. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 11, 2007 Share Posted October 11, 2007 One consideration is that the 2.8L has an externally balanced crankshaft, meaning an eccentric weight in the flywheel (or flex plate). The 3.4L is "zero" or "neutral" balanced, meaning it doesn't have the eccentric weight. I believe you have to use the Jeep flywheel, so it'll have to be rebalanced. ACTUALLY I'm glad that I know this :D IF you have an auto (if you do, please, PLEASE swap to stick) you should concentrate on getting a 3.4 automatic engine, because then all you may have to do is get the torque converter bolts professionally redrilled. if you have a 5 speed stick in your jeep (or 4 speed), then concentrate on getting a 3.4 out of a 5 speed camaro or firebird. then you just bolt the jeep flexplate and clutch in, along with the jeep pilot bushing. be sure to measure the thickness of the flywheel and compare them...if it's thicker, you will need to shave some of the back of your throwout bearing plate down to allow for the throwout bearing to disengage completely (had to do that with the 3800 swap, as the flywheel was 3/8" thicker). I would most definitely avoid complicating things by putting the jeep flywheel/flexplate on the 3.4, if you can avoid it. if not, any competent machine shop can do the neutral balancing, but do not let them machine the clutch surface to a smooth surface, just a light sanding will do. if they machine that, your clutch will wear faster considering that the flywheel was originally machined a bit concave. gas mileage wise, you can expect between 15-19 normally, and highway should be around 21. with gear set up properly, you'll go higher (or lower) depending on what you want. here's some links on it. http://www.lunghd.com/Tech_Articles/Pro ... ect_XJ.htm http://jeep.off-road.com/jeep/article/a ... ?id=277008 and you will need this from bakerelectronics http://mysite.verizon.net/vze7erz1/id1.html it is a VATS bypass (Vehicle Anti-Theft System) that you will wire into pin 55 of the engine computer (dark blue wire). it simulates the VATS system electronic key which sends a OK GO signal to ground the injectors...so it will run for more than 3 seconds :D (you need this if you go with the camaro injection. I will GIVE you the knowledge you need to wire the motor up if you ask.) Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 14, 2007 Author Share Posted October 14, 2007 One consideration is that the 2.8L has an externally balanced crankshaft, meaning an eccentric weight in the flywheel (or flex plate). The 3.4L is "zero" or "neutral" balanced, meaning it doesn't have the eccentric weight. I believe you have to use the Jeep flywheel, so it'll have to be rebalanced. ACTUALLY I'm glad that I know this :D IF you have an auto (if you do, please, PLEASE swap to stick) you should concentrate on getting a 3.4 automatic engine, because then all you may have to do is get the torque converter bolts professionally redrilled. if you have a 5 speed stick in your jeep (or 4 speed), then concentrate on getting a 3.4 out of a 5 speed camaro or firebird. then you just bolt the jeep flexplate and clutch in, along with the jeep pilot bushing. be sure to measure the thickness of the flywheel and compare them...if it's thicker, you will need to shave some of the back of your throwout bearing plate down to allow for the throwout bearing to disengage completely (had to do that with the 3800 swap, as the flywheel was 3/8" thicker). I would most definitely avoid complicating things by putting the jeep flywheel/flexplate on the 3.4, if you can avoid it. if not, any competent machine shop can do the neutral balancing, but do not let them machine the clutch surface to a smooth surface, just a light sanding will do. if they machine that, your clutch will wear faster considering that the flywheel was originally machined a bit concave. gas mileage wise, you can expect between 15-19 normally, and highway should be around 21. with gear set up properly, you'll go higher (or lower) depending on what you want. here's some links on it. http://www.lunghd.com/Tech_Articles/Pro ... ect_XJ.htm http://jeep.off-road.com/jeep/article/a ... ?id=277008 and you will need this from bakerelectronics http://mysite.verizon.net/vze7erz1/id1.html it is a VATS bypass (Vehicle Anti-Theft System) that you will wire into pin 55 of the engine computer (dark blue wire). it simulates the VATS system electronic key which sends a OK GO signal to ground the injectors...so it will run for more than 3 seconds :D (you need this if you go with the camaro injection. I will GIVE you the knowledge you need to wire the motor up if you ask.) it's an automatic, i was planning on leaving it. i wouldn't mind having the torque converter bolts re-drilled. swapping it to a manual transmission would be a little complicated wouldn't it? Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 14, 2007 Share Posted October 14, 2007 NO! it's fairly easy. and that 3 speed auto is a piece of underpowered $#!&. Link to comment Share on other sites More sharing options...
Pete M Posted October 14, 2007 Share Posted October 14, 2007 NO! it's fairly easy. and that 3 speed auto is a piece of underpowered $#!+. As if the AX-5 is some sort of super tough transmission. :D Link to comment Share on other sites More sharing options...
Eagle Posted October 14, 2007 Share Posted October 14, 2007 NO! it's fairly easy. and that 3 speed auto is a piece of underpowered $#!+. As if the AX-5 is some sort of super tough transmission. :D But at least it has 5 speeds. "Back in the day" American car manufacturers did thing bass-ackwards. They put 4-speed and then 5-speed trannies behind the biggest engines, the engines that had enough torque and power to go from a standing start to 200 MPH in a single gear, but behind the smallest econo-motors they only put a 3-speed, meaning it was never possible to get anything close to optimum gearing. If you wanted more gear for acceleration, the engine was racing at 50 MPH, and if you wanted less gear for highway cruising and fuel mileage, first gear wasn't low enough to get started on even a modest upgrade. That's the major drawback to the 3-speed auto, all discussions of "strength" aside. You HAVE to run tall gears to keep the highway RPMs at all reasonable, and that means the tranny and torque converter are working overtime to go uphill or to haul any load. Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 14, 2007 Author Share Posted October 14, 2007 NO! it's fairly easy. and that 3 speed auto is a piece of underpowered $#!+. As if the AX-5 is some sort of super tough transmission. :D But at least it has 5 speeds. "Back in the day" American car manufacturers did thing bass-ackwards. They put 4-speed and then 5-speed trannies behind the biggest engines, the engines that had enough torque and power to go from a standing start to 200 MPH in a single gear, but behind the smallest econo-motors they only put a 3-speed, meaning it was never possible to get anything close to optimum gearing. If you wanted more gear for acceleration, the engine was racing at 50 MPH, and if you wanted less gear for highway cruising and fuel mileage, first gear wasn't low enough to get started on even a modest upgrade. That's the major drawback to the 3-speed auto, all discussions of "strength" aside. You HAVE to run tall gears to keep the highway RPMs at all reasonable, and that means the tranny and torque converter are working overtime to go uphill or to haul any load. in other words it wouldn't be a bad decision to switch to a manual transmission? what about off-roadin? i hear you can get into some trouble running a manual tranny and doing off roadin, especially if you are going up hills. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 14, 2007 Share Posted October 14, 2007 your auto is incomparable to the manual anyways. if you had an aw4 it would be a different story, but the manual ax5 will be better regardless than your auto...you don't have to worry about trans blowing from overheating. Link to comment Share on other sites More sharing options...
Pete M Posted October 14, 2007 Share Posted October 14, 2007 But that auto isn't the end of the world and I still think it comes down to personal preference. If you don't really, really want a manual tranny, you're probably better off with keeping the auto. Link to comment Share on other sites More sharing options...
tkgibbs27 Posted October 14, 2007 Author Share Posted October 14, 2007 rather than going out and buying a different comanche that would be a manual trans. how much work would need to be done to convert a auto to a stick? i like manual trans. better than auto. what i have heard is that auto is better for off roadin' though. i do a lot of off roadin' when i go camping and fishing and i do both pretty often so i would like to fix this truck up to be fit for it a lot more and right now it pretty damn gutless. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 14, 2007 Share Posted October 14, 2007 auto to manual swap is easy enough you'd need ax5 + shifter 4wd shift linkage for ax5 (if you have 4wd) flywheel for manual trans. pilot bushing clutch master and slave cylinder pedal assembly (bolt in) and there may be a minor difference in d.s. lengths but that I do not know. you'd just swap all those parts on accordingly, and no longer use/need any of the auto stuff (auto shifter and cover plate, cable, trans., flexplate, pedal assembly, computer...if it's computer controlled) and you may have to splice a few wires for the sensors on the tranny, but probably will be the same. a weekend's of work. Link to comment Share on other sites More sharing options...
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