Well . . . it appears at lease ONE other person on this list likes sticks,
and knows how to drive them. Should have figured it was you, Gerald! :-)
Dan
75 Argosy 26
> From: "Dr. Gerald N. Johnson, electrical engineer" <[EMAIL PROTECTED]>
> Reply-To: [EMAIL PROTECTED]
> Date: Sun, 28 Jan 2001 18:27:36 -0600
> To: Multiple recipients of VACList <[EMAIL PROTECTED]>
> Subject: [VAC] Re: Towing With A Manual 5Speed Transmission
>
> The tow truck that smokes clutches suffers from the factory quest for
> economy and narrow range transmissions with excessively low rear axle
> gear ratios. I've seen Ford trucks with that problem for nigh on 40
> years. Even farm trucks.
>
> ANY engine needs to turn up to produce horsepower. Say 1500 RPM while
> starting a load. Then the factory axle and first gear set that ground
> speed too fast, the clutch has to be slipped to get the rig moving.
> That's inherent in the automatic. The starting torque of the automatic
> depends on a 3 to 3.5:1 low gear and a 2 to 2.5: 1 ratio in the torque
> converter. Over all ratios 6 to 8.8:1. Attach that to a 4.10 rear axle
> and you have an overall ratio of 24 to 35:1. Meaning that 1500 RPM at
> the engine corresponds to about 1 to 1.5 revolution per second at the
> axle. Ground speed 8 to 12 feet per second, 5 to 7 mph in round numbers
> with 30 inch O.D. tires.
>
> Getting a 20:1 over all ratio with a manual transmission having a low
> gear of 4.72 (ford 5 speed heavy duty) means the axle ratio has to be
> 4.24
>
> Last winter I spent a lot of time looking at a smaller tow rig, F-150
> with small V-8 and low gear in the manual transmission only 3.92. I
> installed 4.10 axle gears. I'm quite happy with the arrangement, there's
> enough torque in first gear to move my Caravel anywhere I want to move
> it in first or reverse (though another 50% speed reduction would
> occasionally be useful and lead to killing the engine less often while
> trying for precision positioning), and enough torque in 3rd gear to get
> up any hill in Missouri at 50 MPH. I toyed with going to 4.56 gears but
> decided I didn't need the additional 1000 pounds starting capacity,
> besides I could get there by change the rear tires from 29.1" OD to 25"
> OD with really low profile 16" tires... A set of tires costs about what
> the gear change did.
>
> Bigger loads require a higher rear axle ratio. I don't think the V10 low
> speed torque will overcome the need for stump pulling torque for
> starting with the 3.83 gears. With that much engine, I'd lean towards
> 4.33 or higher.
>
> In my F-150, the gas mileage was 16 with the old 3.08 gears, and without
> Caravel is till 16 with the 4.10 gears, providing I don't win too many
> times at the stop lights. The Caravel (at 50 mph) dropped the mileage
> down to about 15. Unhooking the air conditioning compressor raised the
> unloaded mileage to 17.8. Running unloaded I generally start in second
> gear because that's the same overall ratio NOW as the prior truck had in
> second gear and that any truck normally has had starting with a 3 or
> 3.5: 1 first gear.
>
> Be very careful about oversized tires, they can kill off the thrust
> gained by high axle ratios.
>
> My neighbor has a 98 Dodge 3/4 ton 4X4 with a V-10 gas. It gets about 7
> mpg empty or loaded (automatic transmission) and with a 32+ foot SOB
> gets that same 7 whether towing at 50 or 70. I have yet to convince him
> that his life is much shorter in emergencies at 70 when stopping and
> control may be a severe problem.
>
> Buying a manual transmission truck these days is harder than buying a
> Lamborghini or new Ford T-bird (sold out in 2 hours I heard). The
> dealers don't want to touch them (their sales staff probably doesn't
> know how to drive one to demonstrate it), and claims they can't sell a
> used one. Several dealers I've visited plain out say, they won't have a
> used manual transmission vehicle on their lot. If they take it in on
> trade they will get rid of some other way than selling it on their lot.
> I bought a '98 F-150 last January that I think had sat of the lot most
> of a year because the claim was that the owner bought a new truck each
> year. They were willing to sell it at a fairly decent price because of
> that time on the lot. I answer the trade in question by pointing out my
> current truck for trading is 14 years old, and my big truck is 35. (Hmm.
> Maybe I should have traded them both?). As for transmission I point out
> that I don't want to pay for the automatic, I don't want to pay for the
> fuel to run the automatic and I don't want to pay for fixing the
> automatic. Fixing and automatic is several times the cost of a clutch
> even in a Ford which may destroy the clutch when the hydraulic clutch
> cylinder fails and sprays the clutch plate with oil. I'd prefer a
> mechanical push rod but they don't make 'em that way these days. I'd
> prefer a NP-435 or Warner T-19 transmission with a 7.3:1 low gear too,
> but that's not available to fit the modern truck.
>
> The stock 5 speed and stock (usually 3.08) gears are NOT suited for
> towing. The highest ratio axle gears the factory installs are often not
> very well suited for towing. I went to a hot rod shop that installs
> gears of any ratio (in police cars too).
>
> I'd get bored with an automatic and frustrated when it shifted when I
> didn't want it to shift. When the day comes that I can't be bothered
> shifting gears, I probably shouldn't be driving but should have a
> chauffeur handling the wheel chair anyway.
>
> Gerald J.
>
>
>
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