Hi im new here but i could use a little help that i dont want to ask my freinds im a little embarased!, i have an 89 F350 4X4 beautiful shape but it has a hard time pulling my boat witch is about 4000lbs with the trailer the truck has a C6 and a 351 on the highway the hills kill it down to about 55 i dont know if thats just how these trucks are or is something wronge
thanks allot

 

give it a good tune up, cap/rotor/wires/plugs, and check timing. if you bump that up 1-2 degrees that should give you a couple of free ponies. don't use overdrive on the hills. (i have auto trans, don't know about c6)

 

theres no overdrive on a c6. its a 3 speed. how many miles are on you truck? and what rpm's are you pulling at. with that motor you might benifit w/ a gear swap. but do all teh basics first. like a good tune up. make sure you get the fuel filter also.

 

the truck has 74,000 miles on it i bought it off the original owner and it also does have 35 inch mud terrains but i thought it could pull a little bit better than it did 65mph is about 2800 RPM any help would be greatly appreciated

 

Stang, I used the your tire size and rpm info and plugged it into the formula: GearRatio = (RPM X TireDia) / (MPH X 336) and came up with a gear ratio of ~4.10, after deducting 250 rpms for torque converter slip in the C6. With 35" tires, 4.10 is kinda high. 4.56 is a good gear ratio with 35's. That will give you some more oomph for climbing hills and towing and your 3rd gear wont feel so much like an overdrive gear.

I run 4.56's with 33's in a '92 F350 CrewCab 4x4 with a 351 and a C6 because the truck had no power with the 33" tires untill I switched from 3.55 gears to 4.56's. It was a big difference. My rpms at 65 are probably around 3200-3300 (I don't have a tach, just going by the formula, plus torque converter slip). That's a little high, so I keep the speed down to 60mph or less and it gets better mileage. With 35's, the rpms would be about 3000 @ 65mph (2850 + torque converter slip). That's still a little high, but these heavy trucks with small engines need more gear to get them going and something has to give. If our trucks had overdrive it would be nice. 4.30 would be a good in-between gear, but it's not available for the 10.25" rear axle that I know of.

Like the others said, make sure the engine is running good, and maybe put a better exhaust on it and if it still isn't enough, either change down a tire size or 2 or swap in lower gears.... My feeling is that Ford should never have put a 351 in a truck this heavy, at least not without very low gears and an overdrive trans. 460 should have been the standard engine.

 

thanks allot for the info i agree with you completely on ford should of never put a 351 in a 1 ton truck 7.3 or 460 only thanks agin