After doing a lot of reading on here I found that my gear code 17 on my 81 f100 meant 2.47 ratio in my 9inch rear end. Combined with the c4 auto trans and 300-6 this is a gutless combo it feels like to me and gwvr aside, could I tow anything with this truck? Who else has this combo and what mpg do you get?

 

I have that rear with a column shift 3 speed. If I mess with the timing and lean the carb out just right, I can do 28mpg on mostly flat highway with a 8 foot long chopper in the bed. I use just over 1/4 tank on a 105-110 mile drive, which I make routinely.

I think you could tow with it decently enough if you do some tuning to make sure you don't blow anything up.

 

28mpg? Are you serious? If I get 18 I will be happy. I try to keep it at or under 60 to keep rpm's down. Gonna buy a utility trailer eventually whether its a little 4x8 or something larger like a 16ft I don't know if it'll handle it loaded

 

Best way to boost mileage in that setup is by swapping in a ZF or T56. I'd say ZF, as 1st is low enough to actually pull a load with those rear gears. The C4 is a little weak for towing, mainly due to it not being as robust as the C6.

 

Yeah man, dead serious. I first time I made that trip I did somewhere over 20, then I became obsessed with maxing it out through tuning. 28 is the peak I can get without pinging or starving the engine. My best 19 gallon tank in mixed, but mostly highway driving did 425 miles. Totally different story in cities, though. Oof.

I think if your transmission is tip top shape and your timing/carb are tuned correctly you could tow a modest amount, just not in any hurry. At least you don't have to worry about burning up a clutch.

 

True, not looking to swap anything though just wondering what my setup can handle. It's definitely non overdrive which I naturally assume the c4 was the trans that year? I believe it has the 11 bolt pan, or the one with the least bolts

 

C4 is the light duty trans. Not really designed for hauling or torque multiplications. Lightweight, but not as stout as the C6. I recommend only small loads. But if you want to sacrifice some mileage, you can easily junkyard your way to a C6 and 3.55's.

 

Is the 9 inch with the removable carrier stronger than most rear ends or cheaper to build or what? I know they are what most high hp race cars use and never knew why, but figure I should be glad that my truck has one

 

Primarily they are used for strength. Ease of swapping gears is a close second. The weak point in your setup is the C4.

 

The c4 is tougher than you think. Just make sure you put a aftermarket tranny cooler on it, and you shouldn't have any problems with it.

The torque convertor's on those old trannies were a little loose sometimes, so that helps with the pulling power. It will let the engine rev up a little more helping with your towing power.

With priorities being fuel economy these days, and also keeping up with 75mph traffic, that combo has it's place.

 

They can definitely be built to handle a ton of torque. I don't know if that's why race builders like them or if because race builders like them that all of the parts are available to build it for a ton of torque (which is the chicken, which is the egg?).

But a big reason race builders like them is the drop-out third-member. They can have different gears set up and change ratios for the day and the track, just by swapping out third members.

(edit: oops, 2 others snuck in between the post I was replying to and my post)

 

Definitely agree with the trans cooler for towing. Considering the 300 found its way into the 250's, your motor can tow. The rear end is fine. Maybe just the trans cooler and a rear end re-gear. The 2.73 gears are great for economy. Just going to have to rev it up a bit.

My Nissan has a 2.4L 4 cylinder and can tow thanks to a manual and 4.9:1 rear gears.

 

... and can be built even tougher. A friend of mine had one in his '79 Mercury Capri (basically a Mustang) that was built to be a bracket racer. With a reverse manual valve body and a tranny brake behind a fire-breathing 351W, when he launched he could lift the front tires off the ground!

 

The C6 is tougher than boot leather. People drag race with them in the stock form. S I couldn't see the C4 being that much of a turd. Some of the AOD's had weak input shafts I have heard. A buddy of mine is going to build a T bucket with a C4. I am sure he wouldn't do it if the tranny was fragile.

 

The c6 is very tough, but it takes horsepower to run it, the racers have less horsepower loss with the c4 if they can beef it up enough to handle what they are doing.