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Just a dumb transmission question

Timmayy

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Reading through all the posts about trans kickdowns I saw a post about not driving without one. In all my years I've never been told this. Will it hurt the tranny? I've always had them myself but what about the guys running various aftermarket shifters? I had a friend back in the 80s that would just downshift manually. I believe he had a B&M auto shifter. Just curious is all.
 
Reading through all the posts about trans kickdowns I saw a post about not driving without one. In all my years I've never been told this. Will it hurt the tranny? I've always had them myself but what about the guys running various aftermarket shifters? I had a friend back in the 80s that would just downshift manually. I believe he had a B&M auto shifter. Just curious is all.
No kickdown, burned transmission.
 
put in manual shift valve body to eliminate kickdown with no harm to transmission
 
An aftermarket shifter doesn’t affect the kick down linkage.

Manual valve body doesn’t need linkage.

you will get about 300 miles out of your trans without KD linkage.
 
No kickdown is how I learned how to dig into a trans. Calling it kickdown covers up what it really does. It's throttle pressure control linkage.
 
Without kick down linkage, first you lose drive, then 2nd, until you end up with just park an neutral. Ofcourse it has to be adjusted for proper pressure or you are still in trouble.
 
I honestly never knew that. Thanks for clearing it up.
 
Years ago, I rebuilt a 727 for a friend to install in a '73 'Cuda he intended to race. I made sure it had the good stuff in it (4.2 lever, 4 pinion planeteries,, 5 clutch discs in front drum, shift kit). what I did not realize, was that he had no kickdown linkage, and wired the lever back when he installed the transmission. He raced it for a couple of seasons. The next Spring, he called to say that it would not back out of his enclosed car trailer that he used for winter storage. He said it drove in OK the previous Fall. I told him he would have to pull the trans, and drop it off to me. This is when I discovered he had the lever wired back. I pulled the oil pan and discovered that the rear servo had pretty well exploded. The sheet metal spring retainer was distorted, and had been forced through the retainer snap ring, and was hanging on the band apply lever, along with the spring. The band apply strut had been folded over and broke, with the pieces laying in the pan, along with shrapnel from the servo piston. Fortunately, the servo bore was not damaged, so the 727 was still repairable with replacement parts. Tying the kickdown lever back replicates what happens inside a transmission if the gas pedal is at the floor with all linkage installed, with all hydraulic circuits in the trans experiencing full pressure. In reverse, this can be 300 pounds. After seeing the damage, my friend acquired the proper linkage for his car.
 
No kickdown, burned transmission.
This has been stated numerous times yet I have driven cars that I bought that had the linkage disconnected and the transmissions were fine.
I think many people repeat this warning without actually experiencing transmission failure from it.
I wouldn't tempt fate by removing it but It isn't like Russian Roulette where you face instant death from it.
 
Ok you first! LOL. if you are going to refresh a trans anyway, then just remove the linkage and let us know how long it lasts.

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In 3rd and reverse the front clutch is applied. Without sufficient clamping force provided by the throttle valve (line pressure +/-) the front clutch will slip under load. Subjecting it to the same conditions repeatedly, it's not hard to figure out what will eventually happen to that clutch pack. I rebuilt a '65 904 for a customer that complained of intermittent 3rd gear engagement. First thing I noticed was that the throttle linkage was adjusted that it only started moving about half-throttle. Second thing was that the friction material in the front clutch pack was almost gone. The linkage adjustment is one of the most important things that should be checked on these transmissions.
 
I agree that it needs to be in place and adjusted properly.
I'm just stating that the warnings that "immediate destruction will occur" are an exaggeration. I had the Bouchillon cable come off of the carburetor of my Charger. I drove 40 miles before I noticed it and that transmission is still going strong in my other car.
Warnings that are based on scare tactics are silly. Smart people will see right through them.
 
40 miles is not going to kill it.

300 miles is fairly accurate. I have seen it plenty.
Yes it depends on how deep foot is on the throttle. Flat ground steady speed will last longer. The big problem is the upshifts to 3rd gear with a heavy foot. It slips before it grabs and eats clutches up.

I’m not a construction guy so I don’t try to see right through your excellent advice on that subject, I just accept it as good advice.

I‘m and ASE master tech and former trans builder. The **** will burn up. No scare tactics, just facts.

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It’s not kick down linkage. It’s actually throttle pressure linkage. More throttle, more transmission fluid pressure. Thus greater hydraulic clamping force of the clutches and bands. Light throttle doesn’t need as much clamping load. Drive it easy? No short term issue. Run it hard without linkage? You can answer your own question. This linkage also modifies shift points. But that’s another discussion.
Doug
 
It’s not kick down linkage. It’s actually throttle pressure linkage. More throttle, more transmission fluid pressure. Thus greater hydraulic clamping force of the clutches and bands. Light throttle doesn’t need as much clamping load. Drive it easy? No short term issue. Run it hard without linkage? You can answer your own question. This linkage also modifies shift points. But that’s another discussion.
Doug
Excellent clarification. Thank you.
 
I
Have a picture of that hanging on my shop wall. I told all my transmission rebuild customers that if their 727 ended up looking like that, there would be no warranty. It clearly had fluid in it, and I told my friends that their transmission was fully warranted UNTIL they put fluid in it! LOL
 
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