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By 46yblock - 13 Years Ago
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Someday I would like to have an automatic trans. The limitations of the '46 manual are TOO MANY. So the question bounces around every now and then. My dad's '56 Olds had to be manually shifted into "Passing Gear". Would a later model auto work by manually downshifting? Anyone have a setup like that?
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By Hoosier Hurricane - 13 Years Ago
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Mike: Manual kickdown will work, however some transmissions use the kickdown rod as a throttle pressure control. Without the rod, shifts will be early, soft and sluggish. Aggressive acceleration will cause slippage on the shifts, and short life for clutches and bands.
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By 46yblock - 13 Years Ago
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Hmm. Thanks John. In the current form of the truck with the 2V carb I havent had any need for additional power passing another vehicle. Looks like the secondaries of a 4V carb would be adequate "passing gear", and smoother too. No manual or automatic downshift needed. Everything in the old truck is a big deal in terms of getting things to fit. Figured a kickdown wouldnt be any different.
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By YBLOCKMERC - 13 Years Ago
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Mike -
I've experienced exactly what John is talking about in terms of throttle pressure. A small adjustment in the rod made a big difference. BTW, I've got a rebuilt MercO from a '55 (I think) that was in my Merc. It has never been run because I decided to go to a C4. It was done locally here in the Seattle area by a guy who was very familiar with these trannys.
Marc
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By 46yblock - 13 Years Ago
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Marc, if I ever go to the trouble and expense of doing an automatic, I want it to be a C4 also. A guy gave me a rebuilt one free three years ago. I checked it out and it is the preferred model, but dont remember all the details. Hey Marc, did you make it to Medford already? Or is the event still in the future?
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By 314 - 13 Years Ago
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anything with a modulator valve doesnt need a kickdown rod.
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By YBLOCKMERC - 13 Years Ago
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Mike -
Still in the future. I'll be coming down Thurs. 6/23 and I'll have that manifold and carb. Are you home during the day?
Marc
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By 46yblock - 13 Years Ago
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Marc, yes my wife and I are retired, slaved to the farm/ranch. 314, it looks like a C4 has a modulator valve according to the search results. Good.
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By MontyRay - 13 Years Ago
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Regarding the question about a kickdown rod for an automatic, as was previously stated, the Fordomatic style automatic transmission without a modulator requires a kickdown rod. The '80-'92 automatic overdrive requires a kickdown rod. Without one, your upshifts will be very soft and it will burn up the clutches and bands if you use anything other than very light throttle. Regarding the transmissions that use a modulator, cruiseomatic, C-4, C-6. A kickdown rod is not necessary IF you never go over approximately 1/2 throttle, but since most people don't drive that way, a kickdown rod is necessary for two things: (1) to make the transmission downshift at wide open throttle and (2) also to increase the line pressure to hold the bands and/or clutches applied.
If you have no kickdown and you go to wide open throttle, you get soft mushy shifts which will burn up the clutches or bands. The reason is that the vacuum modulator will increase your TV (throttle valve) pressure to a certain point, but the kickdown rod supplies additional line pressure to hold the clutches and bands applied at heavy throttle. If you were to manually shift it without the kickdown rod at heavy throttle, you will have insufficient pressure to keep the clutches and bands applied. An example of line pressure (and this varies from engine and transmission application) for a C-6 transmission in a '68 Ford, with the engine at idle (PND21) the pressure would be 55 to 60 pounds. In reverse, 70 to 85 pounds. At wide open throttle stall test, the line pressure will go between 160 and 190 in the forward gears and 240 to 300 in reverse. Without a kickdown rod, the line pressure in a stall test would be less resulting in clutch and band slippage.
A kickdown rod is required for the proper operation of a Ford automatic transmission unless you drive like Grandma. I worked in Ford dealerships specializing in automatic transmission from 1965 until I retired in 1995 and I've seen a lot of transmissions burned up from lack of a kickdown rod.
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By oldcarmark - 13 Years Ago
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MontyRay-Welcome to the site.Always good to have someone with knowledge of automatics.Good info you just gave us.
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By The Master Cylinder - 13 Years Ago
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MontyRay, thanks for the info. I knew the C-4 needed a kickdown but didn't know the why, thanks for splannin' it.
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By 46yblock - 13 Years Ago
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Thanks for your thorough explanation MontyRay.
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By The Master Cylinder - 13 Years Ago
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Mike, the C-4 (among others) are much easier to install a kickdown because you can use a cable. Lokar has a kickdown cable kit for the C-4. That's what I am running on mine, no problems.
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