C-O-M shifting characteristics

C-O-M shifting characteristics

Eric
Eric

May 29th, 2012, 10:48 pm #1

Hi all. I have a rebuilt C-O-M in my '66 F100.

Is it common for it to not kick down over say 50-55mph?

Also...say I make a right hand turn at an intersection without completely stopping and I nail the throttle after I'm turned; the tranny doesn't kick down. I've basically got a green light and I slow down enough to turn and nail the throttle. Tranny acts as if it's still in drive. This makes for some boring acceleration.

Thanks!
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Joined: July 17th, 2011, 7:07 pm

May 29th, 2012, 10:53 pm #2

Check the KD adjustment at the carb. Also make sure the carb goes to WOT when the gas pedal is floored.
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Joined: December 26th, 2009, 4:42 am

May 29th, 2012, 11:36 pm #3

looks good and it will kick down up to 50-55mph. If I'm cruising any faster and punch it; no kick down. It's probably normal but I thought I'd ask.

1966 F100 LWB
Balanced 390 .060 over, Comp 270s, gasket matched F427 intake, headers, gasket matched/bowl blended C8AE-H heads, 2-1/2" duals, C-O-M with 3:54 gears and Tracloc.
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Joined: July 17th, 2011, 7:07 pm

May 30th, 2012, 12:51 am #4


.. up to about 70-80 mph depending on gear ratio and tire size.

Possibly something is a little sticky in the valve body and/or governor.

The lack of KD at low speeds is also a concern. Probably no harm done, but annoying to drive.
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Joined: December 26th, 2009, 4:42 am

May 30th, 2012, 2:46 am #5



1966 F100 LWB
Balanced 390 .060 over, Comp 270s, gasket matched F427 intake, headers, gasket matched/bowl blended C8AE-H heads, 2-1/2" duals, C-O-M with 3:54 gears and Tracloc.
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Joined: December 26th, 2009, 4:42 am

May 30th, 2012, 6:28 pm #6

Surely someone knows the characteristics of a C-O-M.

1966 F100 LWB
Balanced 390 .060 over, Comp 270s, gasket matched F427 intake, headers, gasket matched/bowl blended C8AE-H heads, 2-1/2" duals, C-O-M with 3:54 gears and Tracloc.
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Joined: November 18th, 2004, 4:20 am

May 30th, 2012, 6:34 pm #7

Galaxie "splained" the characteristics. What more do you want?
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Joined: December 26th, 2009, 4:42 am

May 30th, 2012, 6:52 pm #8

didn't know if he was one of the regulars here like yourself; Stuart. I wanted your opinion as well. What about my gearing and tire size? Won't that effect kick down speeds? I know it effects shift points.

I appreciate Galaxies response but it left me wondering...Do I have the tranny rebuilt or is there an easier fix? I need some guidance.
Thanks.

1966 F100 LWB
Balanced 390 .060 over, Comp 270s, gasket matched F427 intake, headers, gasket matched/bowl blended C8AE-H heads, 2-1/2" duals, C-O-M with 3:54 gears and Tracloc.
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Joined: July 17th, 2011, 7:07 pm

May 30th, 2012, 9:10 pm #9


No offense taken. praps I should have explained futher...

As I said, there is probably something sticky in the valve body and or governor.

The KD operation you describe is "not normal".

Valve bodys and governors stick for a reason.... usually trash from wear and tear/high mileage, if not from actual burnt/slipping/damaged friction plates or bands.

The solution? at least pull the pan and inspect for trash. These trannys are not very tolerant of trash in the oil.

A surprisingly small amount of trash can cause problems.

Such a small amount that, on inspection, one might be inclined to pass it off as "not that much trash... how could it hurt it?"

Pull the pan... if it's "clean" then pull the VB and check for sticky valves. Reassemble and road test.

Still got problems? check the governor.

If you find "some" trash in the pan then it's prolly time for overhaul/rebuild.

 
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Joined: December 26th, 2009, 4:42 am

May 30th, 2012, 11:27 pm #10

just dropped a new engine in and I thought I'd replace the pump and tailshaft seals. Fluid was super clean as was the screen filter. Anything is possible so I guess I'll drop the valve body or possibly go to a C-6 instead. Thanks for the clarification.

I'm curious why it kicks down consistently at 55MPH or below. I noticed today that when I make a turn at an intersection; the tranny is only shifting into 2nd. I floor it and it won't kick down from 2nd. I suspect this is normal.
Thanks!

1966 F100 LWB
Balanced 390 .060 over, Comp 270s, gasket matched F427 intake, headers, gasket matched/bowl blended C8AE-H heads, 2-1/2" duals, C-O-M with 3:54 gears and Tracloc.
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