6.9 Engine Swap in My Jeep.

[dieselM715]

Hi guys, I found this site a few weeks ago. I like what I see.

I need some advice. I looking at putting a diesel in my M715. My options are

1) use a GM 6.2 or 6.5 with an overdrive manual, 4.10gears,38" tires

2) Cummins 12v or BT4 with the same drive train.
(would be the most expenive)
3)6.9IDI with the same drive train.

I found a 6.9 in a salvage yard near me. Its an '84/4spd. I don't know what the condition is of this engine. I was planing on doing a rebuild anyway. I looking to use this truck a tow/work truck. I'm also thinking of adding a turbo at some point. I want to stay away from the electronics of the newer motors.I would like to keep this as smple as possable. I might be able to find a GM 6.2 or 6.5 cheaper, but I don't like what I've herd about the blocks cracking or the cranks breaking. They just don't seam to be very reliable. I know I'm going catch heII for saying that, there's allways some who has one with 250,000 miles on it with no porblems. But thats my view.
I have one more questionfor you all

Is the bellhouseing pattern the same for the 6.9 and 7.3 ? The reson I'm asking is I found a ZF5spd from a 88 F350 4x4,it had a 7.3 in it.


Thanks

 

[Diesel JD]

Bellhousing is the same on all the IDIs and from what I understand early PSD as well. The 4bt has the most potential for big HP. The 6.9/6.2/6.5 have the cheap plentiful parts. Any way you slice it, you're into a lot of non stock fabrication, so my 2 bits is to do your homework and go with what you like. The 6.9/7.3 is going to be heavier than the others so you'll need to upgrade the suspension. Any of those motors, especially with a turbo will be way plenty power with a Jeep and get 20+ mpg too I would imagine. The 4BT would get the best the 7.3 probably the least. An O/D transmission or aftermarket O/D would be a wise investment with the high cost of fuel.

 

[6 Nebraska IDIs]

Stay FAR away from any of the early chevy diesels.
They would have been better if had more time to design them but they just werent and be safe.

6.9s are the best for rebuilding, as in they can be easily bored without a care, where 7.3's are already overbored ALLOT making the larger displacement.

 

[82F100SWB]

I doubt you'll have to upgrade the suspension on that M715 to hold up an IDI.. If anything it might make the suspension do something...
The 4BT has been done before, but, there's no reason an IDI wouldn't work pretty well in that truck.
20 + mpg is probably going to be a huge challenge with the sheer weight and gearing(7K+ and 5.38's IIRC) in that rig.
A 6.2/6.5 would just be totally wrong for that rig, they're great for a half ton, but, that's about it.

 

[6.9poweredscout]

seesh, you jeep guys are always stealing our International Harvester parts!! but on the bright side i guess it's better then putting a GM **** in it or a cummins!

-Jon

 

[Diesel JD]

Wait we're not talking something the size of a Rubicon or even a Wrangler.... I'm ignorant on Jeeps and obviously outta line on the 20+mpg if the specs are as the other fellow said. My bad. If that be the case I'd say you want the 6.9 with a turbo or the 4BT's big brother the 6BT.

 

[82F100SWB]

The M715 is a Military 1-1/4 ton version of the old J-Series truck. Very HD, and very heavy, had a Jeep OHC I-6 from the factory.

You must be registered for see images

One with a 6.2:
http://www.ifsja.org/forums/vb/showthread.php?t=20734

One with a 6BT:
http://bbs.off-road.com/ubbthreads/showflat.php/Cat/0/Number/1096188/page/0/fpart/2/vc/1

Great 4bt swap thread, but, his pics are dead
http://www.pirate4x4.com/forum/showthread.php?t=202231

 

[dieselM715]

Thanks guys for the info. Now I just have to start get it all together.
I all ready scored the trany,a ZF5 out of a 89 F350. I picked it up for $300 with the trasfercase. Noe I'm working on getting better axels and the motor.
I found an 84 6.9 in a salvege yard. I have to find out what kind of a deal I can wrk out on it. It has a 4spd bolted to now. When it gose in my Jeep I want to put the ZF behind it.

Thanks again.

 

[firegod33]

Keep us posted on progress! I'll be following this closely, as my daughters and I are conspiring to drop a 6.9 in a '70 Commando.

 

[dieselM715]

firegod, good luck I don't think its going to fit. I'm putting mine in a M715, full sized Jeep truck. I can speak from expreance a Jeep Commando's engine compartment is small compaired to my trucks. A '70's one is even smaller. Thats the short nosed one. Built befoe AMC took over and added 3" to the frount.They can bearly fit a chevy small block,let alone a big diesel.
Sorry to rain on your parade.
By the way I own a '72 Commando

 

[dieselM715]

Here's a pic of my Commando

 

[Diesel JD]

That vehicle would be perfect for a 6.9. About the size of some IH trucks or an F450. I don't think you'll see 20 plus mpg though. If you could get 4.10s instead of 5.38s it would help.

 

[dieselM715]

DieselJD, The truck has 5.87 gears in it now. I'm planing on going to more modern axels,for better parts availablity and breaking and better gears,like 4.10's. I'm also going run 38" tires,with an overdrive transmistion.

 

[RLDSL]

I had the civilian version of one of those critters and it had a 302 ford small block in it and it fit nicely. A 6.9 would probably fit with a can of axle grease and a shoehorn it's pretty open under the hood. I don't think a cummins 6 cyl would fit lengthwise.
With a 6.9 and the axle gears in those things, you could easily climb trees

-------Robert

 

[Timthetoolman]

Let me know if you need an engine, I have a 7.3 crate motor with about 50,000 on it, runs and sounds good. Also have the donor truck if you need some wiring, bits and pieces.