I am currently doing some research on 87-91 f-250 7.3 liter trucks, as I am looking at one. I have yet to look it over personally, but have heard it gets about 12 mpg. That said, and threads I have searched, I would imagine it has 4.10 gears and c6 tranny. (has 32,000 on engine rebuild)

1st question-Are gas and diesel trannys the same, or have the same applications?

2-is there a major difference in gas mileage from regualr, to towing;compared to gas

3-I like to do my own repairs, and am familiar with the ttb, and suspension of the 87-96's. But, I am also a high school student, and soon college, so I won't have money to be rebuilding or doing major repairs, but capable of general maintenace repairs. gaskets etc. Right now i have an 1988 f150 302 33's and 4" lift. It gets 12 mpg, but with the 33's and 302, its just like a stock truck pulling a trailer all the time. I am sick of driving the truck, knowing how much stress i'm putting on it. Would a 7.3 diesel be a good fit?

I have read 3.55 gears and OD tranny will give 5-7 more mpg, but is it worth driving a gas thats gets the same mpg as diesel, but diesel is more expensive?

thanks,
Josh

 

1. Gas and diesel trannies are the same, but they will not interchange with each other. The T 19 (direct drive 4 speed) is the only transmission that was used behind the diesel that has a separate bell housing. Since all the rest have integral bell housings they are engine specific.

2. There can be a major difference in MPG just by changing driving style. Fast takeoffs and high RPM driving can suck the fuel. Diesel engines get the best MPG at about 2000 RPM. So a direct drive transmission like the T 19 or C 6 is not going to give very good MPG running 70 MPH or above. 3.55 gears and 33" tires work out to 2600 RPM at 70 MPH for both trannies. A ZF 5 will be at 1930 RPM using the same tire and gear combo.
An E4OD will be at 1800 RPM with the same gears and tires. As far as while towing, yes it will burn more fuel. But not as much as a gasser towing the same load.
Something else that that enters into this is a diesel 4x4 truck will weigh about 7000 pounds or more, the frames are heavier and all the drive line is heavier. This also means it will be more expensive to repair when it does break or wear out. Take the price of about any gasser part and at least double it to get to the price of diesel parts. That extra weight also makes a diesel seem like a slow poke. Natural aspirated diesels are not speed racers, but they will run for 3 to 5 hundred thousand of miles depending on how they were taken care of. MPG is also dependant on the altitude and terrain they are operated in. A naturally aspirated motor is not going to be happy above 5000 feet, not enough air pressure there for it to run well. When mine was naturally aspirated, I was never the first one there, but I always made it there.

3. IDI diesels are made for the owner to work on. Very simple engine once you understand the principles they work on. Parts are heavy and expensive, but they last a long time. Other than a very few special tools, you can work on most of the truck and engine with a set of regular tools. You may have to get a few larger wrenches and sockets, but that is about it. A regular cab 250 will have the same front axle (Dana 44 TTB) you have under your 150 except it will have 8 lug wheels on it. The extended and crew cabs have a Dana 50 TTB that is the same but a little bigger and heavier.

Diesels are not for everyone. They have what some people call smelly fuel and the same people will say the exhaust stinks. I personally can't stand the smell of gasoline and think gasoline exhaust stinks. Diesels can also be a little contrary when the temps drop below 30 degrees. Once it goes below 0 everything better be in top notch shape or it will not start unless it is plugged in for a couple hours before you want to start it.
This may be something to consider if you live in the northern tier of states or are considering college there, finding a place to plug in may be impossible. If you find one you like and you like the way it drives and runs, we will be seeing you more, I can tell.
Keeping the engine happy is rather easy, oil changes and filter changes is the biggest thing. Coolant monitoring is also important to prevent cavitation. Other than that greasing the driveline and staying on top of wear items is about it.

 

I talked to the kid today, but did not see the truck. He said the truck has about 230,000, but was mostly used to get into the feilds etc. The heads were rebuilt, but I would imagine a few other, simple things were done while it was tore apart.

Sounds stupid, but the diesel and gas frames and suspension are the same, right?

So far he replaced the glow plugs and the brakes. Do glow plugs go out easy? If they don't, I am not sure what to think because you'd think the person who rebuilt it would have done that in the process of the rebuild.

He said it was a 4 speed with overdrive, and was capable of getting 17 once. That tells me, like you said, it was the way he drove it that made him get 12 mpg. I have straight pipe true duals on my f150, and I know what you mean about the way you drive is a variable in the gas mileage.

I am not quite sure what I should do. The truck wont be anymore then $2,000, but I would think at 230,000 miles, and it being a farm truck, the suspension isnt going the be the greatest. We'll have to see....

thanks,
Josh

 

Well I'd say its a good idea if you want something to learn on, knowledge is priceless.

 

All diesel trucks are F350 frames and drivelines, even the F250's.
The gasser F250 could be bought as a light duty or a heavy duty.
The heavy duty F250 gassers were F350 frames as well.



Look carefully at the rear wheel, the hub sticks through the wheel. The hub supports the weight of the truck, you can remove the axles without jacking the truck up. This is one indication of a heavy duty rear axle.
The rear axle under a diesel is probably a Sterling 10.25" axle, it is almost bulletproof.

If you are looking at a 6.9 with a five speed, it must be an 87.