I currently have a 302/C4 in my 52 F3. It's a good motor and I don't have any issues with it. I just put it in and it only has 10,000 miles on it. I drove it from Grand Forks, ND to Shreveport, LA without a single problem. The setup is great except I would love to have a diesel in it. The idea has been in my head for a while. I just ran across a low mileage (40,000) cummins 12v 6bt for sale. The guy also has a rebuilt Allison transmission that would bolt to it no problem. He said this was an older transmission that doesn't have the computer/wiring. I can afford this right now and am going to look at it on sunday. Are there any problems I should look for on these engines/trannys? What about problems getting them mounted in the truck? Any opinion will be very helpful.

 

No issues with the 12 valve cummins. They're bulletproof with the mechanical injector pump. The 5 spd Allison is a great trans too - only quirk is the OD 5th gear can back off the shaft in the OE application. There are aftermarket replacement shafts that are heavier and eliminate the harmonic issues that cause it to vibrate off.

Downside: It will weigh twice as much as your 302/C4 combo. You probably have room under the hood, but might require reconfiguring the radiator. Some simple measurements will tell you.

I've been wanting to do this swap in my F6. I have the 6bt turbo edition in my 97 D2500 and it's a torque monster that gets 15-20 mpg. The non-turbo 6bt tends to be a bit doggy - typical diesel.

 

I called the guy back and the transmission is a 4 speed from an Ottawa truck. I'm guessing that wouldn't be a good tranny for my truck. I've been looking online to find any info I can but haven't got far. I originally thought about putting in a NV4500 but got excited about an Allison. Now I'm just not sure about this tranny.

 

Might need to box the frame and such, lot of torque.

 

I was planning on boxing in at least the front part of the frame and beefing up the front leafs. Would it be better to box the whole frame?

 

Another question: What would be the best way to beef up the front suspension? I have the original leafs and axle on it. The flathead weighed in at 525 pounds and the cummins weighs in at 745 pounds. I'm thinking about addind a leaf or two. Any thoughts?

 

Don't discount the 4speed allison. We had them in the trucks where I worked in the 80's, they were great transmissions. We beat them and they never broke. Only disadvantage is they do NOT have an overdrive (at least the ones we had). I almost went with a 4bt....but decided against it. Personally the way diesel fuel is going (UP) I would probably steer away from it. If you do pull the plug please take plenty of pictures. Thanks,

Paul

 

I agree about the allison trans. We had them in 10 wheeler tank trucks and we beat them like a rental car and we never had a failure.

Besides it would really solve a driveline issue. With as much torque as you are going to have how much rear gear do you need anyway??? 4spds and a small gear plus huge torque shouldn't be a problem.
jim

 

I think the issue is too much gear, the diesel will run out of RPM on the highway unless you have a lower (number) rear gear ratio or OD.

Is it F-4's and higher that came with double-wall frames?

 

Ross, yea, I think the double wall frame started with the F4's

I once ran into a guy that had a 4cyl Isuzu diesel in a 1966 F-100. I'm not sure what he had for a tranny. He told me that an equipment dealer out in west Texas did the conversion years ago. It was an interesting truck and a very clean install

Bobby

 

I would ad at least 2 leafs and make sure your old ones are in good shape. A 200# increase in weight isn't that much(think about adding a winch or standing on the front bumper) so as long as your springs are in good shape and you add a couple then you should be good. I know my stock 292 and 4spd weigh almost 800# combined.

 

I'm running a 4:11 gear Dana 60. I only want to run the truck about 60 mph. Any more than that just doesn't feel comfortable to me. I'm guessing that the 4 gear ratio would be a 1:1. My tires measure about 31 to 32" so I would be running about 2600 rpm's on the highway. Should I be aiming for a lower rpm?

 

My front springs need to be replaced so I'll be starting from scratch on those.

 

I think you are refering to the NVG4500 trans, a manual 5 speed. I have just finished rebuilding 2 of these for that very reason.
You're a little off on this figure, add a little over 200 lbs. A fully dressed 6BT ready to go is a little under 1000lbs.
The 4 speed Allison is going to be way too big for your truck unless you want to build a huge trans tunnel for it. Also, it has no park brake.

 

Great. This will help a lot. The guy said the transmission looks like a turbo 400 on steroids. His words, not mine. I have yet to see this stuff.

I measured the truck last night and looked at diminsions for the 6bt online. It looks like it's going to be a tight squeeze to fit it in there. I'll measure the motor sunday to make sure. I might have to go with a 4bt it this doesn't work out. I really want the 6bt though.