Hello all,
I'm currently driving/using an 85 F250 with a 351W, C6 and 4wd. I'm converting to a a 6.9 Diesel as I want more torque for pulling my travel trailer around, and I've had heating issues while plowing the big farm driveway with the 351W. For the conversion I've purchased an '85 F350 Diesel with a C6 and 2wd. I know the C6 transmission has to stick with the diesel and I know converting it to 4WD is a complete tear down and rebuild. I'm perfectly fine with that as I'll just put new clutches etc in it and rebuild it. (My current C6 is finally starting to slip in my gasser so I'm due for a rebuild either way!)

So, I have a few questions:
1. Are all C6 4wd output shafts the same? Can I swap my C6 gasser output shaft into the diesel for the 4wd conversion? Or better yet I'd like to just pick up another C6 4wd output shaft to put in so I can keep my gasser together as long as possible. I just haven't been able find a great definitive answer for this.

2. I know you can rebuild a C6 as a wide ratio. Is that of any advantage on the diesel or would I be better off sticking to the close ratio on a stock rebuild? I know it'd give me better plowing/towing torque, but due to the low rev line of the diesel... Looking for input on this one.

3. I'm assuming the innards of the C6 gas and C6 diesels were the same? There doesn't appear to be any differentiation of gas vs diesel on the rebuild kits I've seen either. Any recommendations of rebuild kits/manufacturers? It seems the red alto clutches etc are pretty popular.

I'm hoping to get the engine tuned up and ready to go in the current chassis, then pull it, rebuild the trans for 4wd and mate it all up so I can pull pull the engine/trans from the gasser and drop the diesel right in. I'm figuring I'll be going turbo on it at some point so I'm debating doing ARP head studs and new head gaskets. I guess I'll find out this weekend as my new glow plugs are here (all but 1 were burned out) so I'll know if I'll be planning to pull my heads or not. If I have to pull them she's getting ARP studs and thinking I may add the 7.3 turbo valves.

Thanks for all the good threads on the GP's. I made sure to get the good ones, not the craptastic ones the local big box stores sell! I miss the diesel tractors... next best thing is a diesel truck

And thanks in advance for the input about the transmission questions!

Chris

 

Chris,
it would be much easier,and cheaper to sell your 2wd and just find the 4wd truck.

 

1. Are all C6 4wd output shafts the same? Can I swap my C6 gasser output shaft into the diesel for the 4wd conversion? Or better yet I'd like to just pick up another C6 4wd output shaft to put in so I can keep my gasser together as long as possible. I just haven't been able find a great definitive answer for this.
Yes. Since all transfer cases bolt to all 4wd transmssions, the output shaft will be the same. Now is the output shaft all you need to convert it to 4wd? I am not sure, but I think there are a few more parts you will need.

2. I know you can rebuild a C6 as a wide ratio. Is that of any advantage on the diesel or would I be better off sticking to the close ratio on a stock rebuild? I know it'd give me better plowing/towing torque, but due to the low rev line of the diesel... Looking for input on this one.
If it's not too difficult, I would definitely try it. I didn't like how sluggish the c6 was with the diesel, and the lower 1st gear may help that.

 

agreed.... if I didn't have a sandblasted and repainted frame and bodied cab on my current truck along with new fuel tanks and brake lines and master cylinder and calipers and steering motor etc etc... Plus I got the 2wd diesel that runs great for 500 bucks. I doubt I'll find anything close to a diesel 4wd in even half the shape of my current truck for anywhere near the price. Tearing apart the transmission doesn't bother me, I've had 'em apart before. I've got several 2wd C6 transmissions around the farm, but the only 4wd is in my current running truck. I'd lay it up longer if we could ever depend on the Chevy truck. Diesel front suspension on the 4wd is already taken care of for the extra weight (did it with the gas engine to help with the plow weight). I converted my carburetor on the gas engine to a home built EFI system (machined an adapter plate to bolt a GM TBI (I felt dirty doing it) to the stock 4bbl intake). Doing it isn't an issue by any means.. I just need the info. I'd prefer to get it by asking than learning the hard way by doing. I've got a lead on a diesel 4WD c6 so the conversion of the trans may be a non-issue, but I'd still be curious about wide ratio with a diesel and recommendations for who has the best clutches/bands etc. Plus I'd rather have a good fresh transmission for plowing and towing than just buying something with 150k+ on the trans that'll poop out shortly after I get it.

 

Thanks Franklin2.
I know that the tailcone/extension on a 2wd vs a 4wd is different, but it's the output shaft that you have to disassemble the transmission to change out, and I know the output shafts for 2wd and 4wd are different. The tailcone/extenion is the easy part.

The wide ratio is basically swapping out the forward planetary gear set. With the upgrade you can go from a 4 planet set to a 6 planet and it gives you a 10% lower geared 1st and a 5% lower geared 2nd while leaving 3rd 1:1. Total cost for the planet set/ring gear/sun shell/bearings is around 250 bucks. You could also just drop in the E4OD planetary I guess (4 planet gears) as it's what the original wide ratio swap was, however I'd vote for the upgraded 6 planet set for the extra strength.

Stock C6 1st 2.46, Wide Ratio 2.72
Stock C6 2nd 1.46, Wide Ratio 1.54
And in both case 3rd is 1.0 ratio.

 

I don't know how far you from kenobuck, but he is planning on pulling his C6 and using a T19.

 

My vote is convert over to 4x4. I'm planning on doing it myself.
Check this out - https://www.ford-trucks.com/forums/8...is-to-4wd.html

Converting 2wd to 4wd can be cheaper than selling a good 2wd and buying another 4wd...it's about how you do it

Buy a '86-91 F350 4x4 with a blown engine, there's your $400 parts truck.
Pull everything off the 4x4 truck and clean it up. Swap it all over to the 2wd rig and now you've got a 4x4. Sell parts off the parts truck and I bet you'll actually make a profit from the project.