Peculiar problem 727 manual valve body

Hi fellas

My 727 manual valve body does not engage in 2nd gear under WOT but does so under moderate and light load, No problem doing burnouts in 2ngear. I have adjusted the kickdown band per factory recommendations. What could explain this?
I had to throw my Charger from 1st to 3rd at the race last weekend. Nevertheless I did a best of 11.72 with that method (my best while the gears were OK was 11.63). These 451 strokers are torque monsters.

Thanks for coming up with possible solutions.

Ragnar in Iceland

Most manual vb’s don’t use the linkage. Is it a stock vb with a kit? My transact vb has no provision for kick down linkage.

[qte=rickraw]Most manual vb’s don’t use the linkage. Is it a stock vb with a kit? My transact vb has no provision for kick down linkage. [/quote]

I am referring to the kickdown band (the front band) not the linkage.

My bad.

How’s the detent adjustment.

I would do an air test of the kickdown servo. A malfunction there would show up less under light-load conditions.

Thanks guys. Opened the pan and found small and very fine threads of metal in it. So an overhaul is imminent and will reveal the cause.

Ragnar in Iceland.

I suggest before you start taking it apart, check the behavior of your shift linkage in ALL gear position,particularly 2nd gear. Not all systems hit all the detents equally. The confusingly named kickdown band is a giant part of 2nd gear.We are asking this band to stop and then hold a heavy front drum under full power.Much bigger job than the low band which just needs to hold from a much lower speed. An aluminum front drum, being lighter, should theoretically help in this situation.I described fighting this situation in another post involving clutchflites.I learned about the importance of keeping an eye on the kickdown band adjustment, especially in a heavier and/or higher horsepower car. Not at all a difficult task.
With an assistant (easier,but not required) move shifter one postion at a time and individually check lever for full engagement in each position, meaning shift cable pivot can be moved in and out of lever with no side load. Just checking in Park or Neutral is not enough. Both the shifter lever and manual lever move in an arc, so you can see where variations could be evident. I failed to do this after a rebuild,and on two weekends had a trans that went from 1st to 3rd,skipping right by 2nd under full load. Didnt see it on burnout or light load either. Thought problem was internal caused by my rebuild.Thought about linkage and did the test I just described.There it was.Revamped linkage a bit to ensure lever was fully engaged in 2nd gear and trans performed correctly. No more problems and kept an eye on kickdown band adjustment.Good luck Bill

Especially with cable shift. Been down this trail as well.
Doug

If you look at the power flow the only two elements being used in 2nd are the forward clutch and the 2nd gear band, the forward clutch is applied in all the forward gears so that could be ruled out. 1st step in any transmission diagnosis is a pressure check, and the 727 has plenty of test ports to hook a gauge to. If possible you may need to hook up a gauge and tape it to the windshield and make a pass to watch the pressure. You must correct the cause of pressure loss first. You may get wet but you can check the band apply servo with air pressure in the car and the valvebody removed. The flat plate that goes to the band anchor can flex or even have cracks, check it over close.
I am prone to believe that you may have some chassis flexing that is pulling your shift cable, and causing the manual valve move out of the detent. I have had it happen to me more than once. Seems every time I R&R my engine or transmission, I always have to readjust my shift linkage after a couple passes, for some reason, even after I am super careful to get it right in the shop.

Thanks again guys, for well thought out comments. I have checked the movements of each shift through an open pan, and can not see any deviation. I will report the results of the tear down when I get to it. I am currently waiting for an overhaul kit I ordered from Summit last Tuesday. It is scheduled to arrive in six days and the final price will be double for what you racers pay in the U.S, due to shipping charges plus value added taxes. Oh the price you pay for participating in auto racing

Ragnar in Iceland