Re: [VAC] Towing with a Ford manual transmission

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

I've started with the factory towing ratings and computed from there.
This 4.6L v-8 is rated at higher torque than my old 302 (that broke) but
not in towing. With the 4.10 axle in transmission overdrive it will be
like driving in straight through 4th gear in the little ford 5 speed
manual. As I become acquainted with this 4.6L engine it seems to be
happier for torque the faster it is running.

The torque converter and the 302 with 3.08 or 3.55 has a considerable
towing capacity, well over 5000 pounds. Low gear in the transmission is
about 3:1 then the torque converter will give another 2:1 for starting
to give a 6:1 low gear effectively. My 302 had a Warner t-18 4 speed
manual with a 6.5:1 first gear. It pulled as well as an automatic. I had
7000 pounds behind it on one occasion without working it hard. Without
tongue weight and wagon brakes, stopping was overly exciting even from
20 mph.

The closest thing to a two speed rear axle that is available are the
overdrives from Gear Vender and another place with your choice of over
or under drive as an auxiliary to fit in the middle of the drive shaft
or that bolts to the back of the transmission. Do a web search on
"overdrive" and they should come up. The cheaper one is about $2245 plus
$500 installation, the other is $3250 plus $700 installation. The ratios
are about .73 to 1 in the overdrive 1.25:1 for the underdrive. Not as
much change as I wish, and even if either would save a quarter of the
fuel I burn annually, it would take 25+ years to payback for me. But
then I only drive about 8000 miles a year. A local hotrod shop will swap
the rear axle gears for about $500, I don't yet know the cost of
speedometer calibration, and I can own a couple pairs of drive tires for
another $500 or so. Swapping tires isn't as convenient as shifting on
the go but its relatively inexpensive and rather reliable (e.g. no
additional parts to break). I'll need to add traction bars to the back
springs to keep them from being wrapped around the axle when starting.
$42 from NAPA in paint, $62 in chrome.

My plan today is to go with the 4.10 gears and the stock tires, but
first I need to run a tank of gas through it before modification to set
a baseline fuel consumption. Probably I'll stick with the stock tires
until I wear them out and then consider larger/smaller tires for the
next set.

Gerald J.