schmenke

The OP is saying the truck experienced no squat, so it doesn't sound like he's exceeded his payload limits.


Possible causes:
- Like others have mentioned, altitude.
- Underinflated tires. I know this sounds simple but it would definitely contribute.
- Aerodynamic drag from the trailer. The OP said he's only ever towed around the city, likely short distance drives at relatively low speeds. A cargo trailer is typically far from aerodynamic, so drag would certainly start to become a factor at speeds approaching 45mph, especially combined with the two factors mentioned above.

Dirttracker18

If the trailer was loaded well he may have a low tongue weight but high actual weight in the trailer. Without knowing for sure, we and he are just guessing.

acadianbob

When your truck shifted to 3rd gear, it didn't have enough torque and horsepower at THAT RPM to hold your speed. So, it slows down and then downshifts; gains enough speed to shift to 3rd; and then can't hold it again.

I don't see a problem. For the weight you are pulling; it is reality. You can talk about maximum horsepower and torque; but if the actual RPM is below where your maximum torque is peaked; what you have experienced will happen.

swak6287

my 12 5.0 with 3.31 had heaviest tow at 7000lbs TT and did not have that problem either. I agree, might want to check into it. But Dealer gonna say "cannot reproduse problem".

McCarthy

Thanks for the replies guys. Payload is 1400 and change on the door. ~120lbs over loaded, but that doesn't explain the lack of power... the trailer had two 3500lb axes and was rated for 5000lbs of cargo. I didn't have it on a scale, but the load was boxes of stuff, and I weighed each before I loaded the trailer so I could distribute the weight properly, which is where I come up with the estimated trailer weight. (weight of trailer + cargo = total) A bit of altitude, but not much, 3800 feet.

flat ground I locked out 5th in tow haul and it would hold 60mph. If I wanted to go the 70mph speed limit it had to go to fourth.

redranger04g

If the trailer is equipped with brakes, could be dragging brakes. Just throwing out another possibility.

Tachdriver

Have you changed to larger tires than from factory? If so you have changed your drive ratios as well.

Also 3800 feet feels to your engine at 46 degrees F. Any warmer the air becomes less dense so your engine puts out less power as well.

schmenke

It's more a function of altitude. Air density and altitude are inversely proportional. The higher the altitude, the less dense the air.


But yes, both points above are valid.

McCarthy

Very cool day. 8c and rainy, that's like 45f ish.

Stock size BFG KO2's once the garbage pirelli's wore out a while ago.

Tachdriver

I explained this in more detail...thanx