I finally found a good mechanic who is helping me with my engine swap, I chickened out due to lack of spare time. When I was dropping the truck off I asked him about swapping gears in the diffs for me. He gave me a great price, now I need to know where to buy the parts as well as what gears to go with. I plan on pulling a 6500 pound trailer on a semi regular basis, so towing performance is a primary concern, I have a car for daily driving and gas mileage. The truck is an 89 with a 351 and c6 transmission. Would 3.73 gears be ok? It has 3.07 stock I think. What have other people done and what were your opinions.

forgot to say... I'm running the stock tire size and have no plans to ever increase diameter.

Thanks

 

Suggest to first be sure what gears you really do have. IIRC, the two options were the 3.08 and the 3.55.

The 3.73 would be a 20% increase for the 3.08, but only about a 5% increase as compared to the 3.55. This would represent increase in available torque, increase in engine RPM for the same actual speed, and increase in speedometer error - reading faster than actually going.

How does the vehicle pull the trailer now?

May also want to consider an auxiliary tranny fluid cooler, if it doesn't already have one.

You didn't mention whether it was 2WD or 4WD - the point being that if 4WD - you have two sets of gears to buy.

Many members have had success with lmctruck.com or rockauto.com. I have been pleased with rockauto.com, haven't tried lmctruck.com - yet.

The 1989 351 was rated stock at 210hp at 3800rpm, 315ft-lb torque at 2800rpm - may want to consider some performance mods to help with your towing efforts - the late 80s were tough times for horsepower with the emissions regulations. The 302 was rated at 185hp.

IIRC, and sometimes I don't, but Ford resorted to giving away the 351 as a free upgrade in place of the 302 on some vehicles in order to meet fleet emissions averages. Apparently they were having troubles getting the 302 cleaned up. -- Sorry, just useless trivia bouncing around in my head - can't flush it out no matter how many beers. :-)

 

I wish that was the useless trivia bouncing in my head

 

So based on that statement, I should probably target 2800 rpm at a decent speed since that's where I'll get the most grunt. I haven't driven the truck enough yet to know what speed=what RPM, I just got it and am replacing the engine right now, little did I know it suffered from low oil pressure when I bought it.

I don't have the trailer yet, and my first big towing experience is going to be a 1200 mile trip, so I was trying to prepare all I can before then. I've already got a temp gauge and trans cooler to install with a shift improver kit. I thought that getting an older truck to pull with would be fun and different, I think my old F150 has more character than my friends new trucks. Plus everything I read about says the 351/c6 combo is a pretty bulletproof drivetrain.

What engine mods would you do to get more HP? Reliability is a must as well as I'd like to keep some green in my pockets at the same time. I also don't mind useless trivia about these trucks, I'm new to the F150s so chances are that the trivia is new to me.

 

I have an 81 F150 with the 302W motor. 4x4, regular cab short bed. I pulled my open trailer that weighs maybe 2000lbs(?) and i had my 2800lb race car on there with a generator and tools. Maybe over all 5000 to 5500 lbs. The big thing for me was the tongue weight. I think the motor and tranny will be more than enough. The rear gear has been changed in our truck but wasnt a big difference. I would suggest getting a brake controller(good one) and possibly a weight distributing hitch. Also I would go up in the gears also. 3.73 would probably be perfect. Just my .02