Auto trans shifting early
 

When I built my cobra I installed a c6 auto trans out of a mid 80's 3/4 ton ford f150. Of course I modified it and installed a B&M shift kit. It runs fine and shifts are precise.
Here is the problem: The transmission shifts to early at full throttle (4200 rpm). Does anyone have any suggestions on where to look for the early shift problem? I need the trans to shift at 6000 rpm.

There are three things that control the rpm shift point on a C-6. I would not be surprised if a 4200 rpm shift point is the result of a perfectly working "stock" C-6 trans. Want a higher shift point? You may have to tweak your "shift kit". I'm guessing it's your "modulator" thats the problem (assuming your shift kit is installed and working correctly).

Valve body: Controls auto or manual shifts depending on whether it's "stock" or "modified" for performance, rebuild/modify kits are available. This is the most common "modification" on a trans for perfromance. The VB is what your gear shift acts on to select what "gear" you want.

Modualtor: Adjustable, usually controlled via the throttle linkage that goes down to the trans. Should be fully "engaged" at or near full throttle. If NOT, "early shifts" WILL occur.

Governor: At a certain rpm "over rules" the modulator and forces a "shift" anyway. It's action can be "over ruled" by the valve body. Generally not easy to modify like the VB is.

The modulator MUST be hooked up or the trans shift points will be a nightmare. Raising the shift points increases the internal hydraulic pressures that act on the clutch packs and the "band" for 2nd gear. A "race" trans will have more aggressive longer wearing clutchs, the "band" and the planetary gear set is also "beefed up".

A stock C-6 with a 400 hp engine in a light weight Cobra SHOULD hold up OK. More than 400 hp COULD result in early failure.

Ernie

ANY SUGGESTIONS ON THE GOVERNOR, Excaliber?
Thank you for giving me a new route to persue.
I just do not have the working knowledge (that I need) for auto trannies. thank you for your time

Man that governor is not going to be easy. It's in the tail shaft area and I'm not sure HOW it should/could be modified. But if the modulator is in fact FULLY depressed at full throttle with the modified valve body you've got all ready, the "gov" should not be a "major" player in this early shift problem.

Normally when a guy gets a "shift kit" (modified valve body) you specify what kind of "control" you want, and the kit is designed for that. Different size ball bearings, heavier or lighter springs that operate the little sliding valves etc.

You can spec the VB to give you HARD QUICK upshifts, or early soft shifts (not common), or a "manual" valve body. With the "manual" the trans won't shift at all untily YOU move the shift lever.

Perhaps you should check to see WHAT kind of "shift kit" you got? It sounds like it's totally stock, just got a good "brand name" on it.

You CAN buy a "shift kit" and install it yourself, it ain't "that hard" actually. Pull the VB, follow the instructions, remove spring "A" and replace it with the kits spring "AB". Take out this ball bearing and leave it out, put this new one in "here". Kinda like a puzzle, but it's not bad to do!

Ernie

Watch out for the "oops" springs. You know the ones that fly out and you go, "Oops". :LOL: