78 Miles

[Tom Wells]

Buzz,

You said

One thought - have you considered (if it's even possible) putting a manual valve body in the slushbox? You'll still be clutchless and at least you won't have to worry about unpredictable up and down shifts. In a high powered Cobra, you want to make sure you're in full control. With all that torque, a surprise shift while negotiating a sharp turn, changing lanes to pass or accelerating on a damp off ramp could ruin your day in a real big hurry my friend.

Is this based on experience, or is it speculation?

I've run my automatic at Sebring, Daytona, Gainesville, Roebling Road and others for literally hours at my limit without any difficulties induced by a "surprise shift."

I have had, um, unexpected directional excursions but none could in any way be linked to the trans - only to my lack of skill!

I'm curious as to what experience(s) you may have had that prompted you to make this remark. Seems to me the incidents you propose as dangerous could also be accomplished with a stick shift, and seem to involve accelerating in inappropriate circumstances not related to the type of trans.

Can you enlighten me?

Tom

[Car Nut]

Nice meeting you last night Tinny and as others have said, we feel your pain.

I see the transmission you used started out life as a 4R70w which is a computer controlled Ford automatic overdrive. These transmissions come with an intergral torque converter housing that mates to late windsors or modular motors and require a modfication and an adapter to fit the FE motor.

The internals really need to be worked over too to handle the additional power as in stock form are supposedly good for a maximum of 400 hp.

Finally a computer control operates the transmission which controls up down lockup firmness and all other aspects of the transmission.

They can be made to handle over a 1000 horsepower.

Your gear hunting problem is most likely a matter of seperating your shift points and throttle position settings.

As far as the rest of whats going on I don't have a clue, but I would really suspect an issue with the fitment of the transmission, correct clearance between the torque converter and flexplate. Not enough clearance and it will eat the thrust bearing out of the motor and/or ruin the front pump of the transmission.

I am mentioning this because when the find the cause, you may have other damage that is not immediately apparent. I would be very insistant that you are properly informed of what they find and what they check for.

[Buzz]

Originally Posted by Tom Wells

Buzz,

You said
One thought - have you considered (if it's even possible) putting a manual valve body in the slushbox? You'll still be clutchless and at least you won't have to worry about unpredictable up and down shifts. In a high powered Cobra, you want to make sure you're in full control. With all that torque, a surprise shift while negotiating a sharp turn, changing lanes to pass or accelerating on a damp off ramp could ruin your day in a real big hurry my friend.


Is this based on experience, or is it speculation?

I've run my automatic at Sebring, Daytona, Gainesville, Roebling Road and others for literally hours at my limit without any difficulties induced by a "surprise shift."

I have had, um, unexpected directional excursions but none could in any way be linked to the trans - only to my lack of skill!

I'm curious as to what experience(s) you may have had that prompted you to make this remark. Seems to me the incidents you propose as dangerous could also be accomplished with a stick shift, and seem to involve accelerating in inappropriate circumstances not related to the type of trans.

Can you enlighten me?

Tom

Tom, first off, I don't want this to become a perceived issue of defending an affront to automatic transmissions in Cobras. I have owned and driven a few high powered auto trans cars but never in a light, short wheelbased car like a Cobra. I am no expert in the field and my thoughts are based on HIS experience with THAT transmission and engine combo.

I acknowledge your experience with your car but I stand by my position that unpredictable up and downshift hunting as well as "grabbing" - which I interpret to mean harsh or hard gear changes - in a Cobra with 572rwhp/566tq can land an inexperienced driver in serious trouble under certain not-so-far fetched circumstances. You are right in saying that the same problems can occur in a manually shifted car, but at least the application of power and torque multiplication are fully within the driver's control. Not so in a malfunctioning automatic.

Car Nut seems to know a lot about the 4R70W transmission and if he and others feel it can be tamed and made to function smoothly and predictably behind John's 511, then problem solved.