Re: [VAC] Re: V10 Dodge as tow vehicle

["Dr. Gerald N. Johnson" <geraldj@xxxxxxxx>]

No outright formula that I know. Probably could be worked out using the
first gear and rear axle ratios along with factory rating for trailer
plus truck (Gross Combination Weight) to determine the thrust and the
slope needed... Also need tire diameter and torque converter ratio at
stall if an automatic transmission. Since each engine has a different
speed/torque curve, I don't know what engine speed or torque to use...
There may be an SAE standard for the computation complete with formula.
Maybe some one with a recent SAE standards book could search for it.
Mine is 20 years old and I don't know which pile its in.

To add confusion, some years of Dodge trucks have the same trailer
rating ignoring axle ratio. Even Ford's '98 ratings are inconsistent the
3.55 axle pulling better than the QCW ratio between the 3.08 and 3.55
axles would predict.

I based my computations on the 3.55 axle (I think). The truck weighs
4340 pounds. Trailer rating was about 3500 pounds, GCW about 7840
pounds. Multiplying by 4.10 / 3.55 gives GCW of 9054 pounds, 4715
trailer pounds. Going to 4.56 rear axle (via gears or tires) gives 10070
GCW, 5730 trailer. Gears cost me $480 installed, speedometer gear about
$20 more. If I change the tires I can get an electronic speedometer
corrector from Australia for $88 US and keep the speedometer gears I
have. That won't work with older trucks using a cable instead of
computer.

I've thought that once I wear out the original tires, that I might buy a
pair 26" diameter and another pair 32" diameter. For cruising unloaded
I'd rotate the tires to put the 32 in the back and the 26 on the front.
For towing, it swap them end to end... Far quicker than changing gears
in the axle and wearing them in. And if tires are needed, not much of an
extra expense.

Gerald J.