727 shifting pattern problem

[hemi68charger]

OK,
Here's the gig.... The tranny will shift into 2nd from 1st, even if the gear selector is in first. I have made sure the linkage is adjusted properly. I can go down the road in 1st, and it stays all day long. But, if I nail it, after a wee bit, the car shifts into 2nd. But, it is in first gear selector..... Grrrrrrrrr...

The valve body is a Cheetah by Turbo Action. My friend mentioned the valve body was modified such that the fluid could be checked in park as well, didn't need to be in neutral running.......

any ideas.....

[ws23rt]

There are several things that can cause shifting trouble but when you say it will shift when the selector is in first I would say something is amiss in the valve body. Modifications to the valve body for one purpose can have an affect on another.  In other words a package modification is needed.

Valve body swaps are fairly easy and a quick way to isolate the problem.

[A383Wing]

Troy...that might be normal....especially with an after-market trans kit....maybe something to do with over-revving  the transmission stuff inside?

I heard in the past that GM's TH-400's will go to 2nd even if the shifter is in 1st for some reason..and this is on a stock trans....I have not tried it with my Pontiac trans

[cudaken]

 Tory, have the car is first running with someone behind the wheel. Then crawl under the car and see if you can move the selector arm anymore. If it stays in first, then the linkage is off. If it shifts the same, it is the vale body.

I have never ran a Cheetah Turbo Action vale body. Is it a full auto or semi auto? I ran a TCI Semi Auto and loved it. Well till a detente went bad! Shifting to 1st at 40 MPH in a BB Cuda will put hair on your chest!   Problem was the Slap Stick, not the 727.

Cuda Ken

[John_Kunkel]

Besides a valve body problem there is the rare possibility that the left engine mount is broken, this causes the engine to climb when throttled hard and this can actually shift the trans to shift out of first gear (especially column linkage).

Set the parking brake, hold the brakes firmly with your left foot, put the shifter in "1" then throttle hard (stall the converter) while someone observes the engine from the side; if the mount is broken the left side of the engine will climb more than usual. A long pry bar between the frame and exhaust manifold will show the same thing.