85 vette, 7004r, stuck in 1st gear, has reverse and park

[Quick6'n'-K.C.]

guy down the street has a 85 auto vette that was/is having trans issues-

i looked at it saturday night, the TV cable was really loose, and the car STILL sticks in first gear, will not upshift-

The guy went to a local speed shop, and the guy says that there is a sensor on the side of the trans keeping the car from upshifting??

anyway, the speed shop guy says this sensor is located on the pass side and i dont have a clue with the chevy overdrive trans-

does anyone have an idea what it could be?
i teased him that it needed a turbo buick motor and trans, but he says V8 all the way-

the car stays in first, no other gear other than reverse, park works great-
any help would be appreciated
BW

 

[savage6]

My uncle who is a car dealer has had this problem before and when he took it in they said it was the "PNP" switch. Maybe this is your friend's prob too?

Just a guess, hope that helps!

 

[MeanBuicks]

The transmission is in 'limp' mode. GM designed the TV system to default to maximum line pressure in the event the TV cable becomes disconnected or broken. This protects the clutches against burning up prematurely.

This is done via an exhaust checkball that is normally held off it's seat by a plunger. When the TV cable develops too much slack, the ball seats and pressure maxes out. It usually won't shift out of first unless you run it up to about 5000 rpm (ala WOT shift point).

Investigate why the TV cable is soo loose, rectify that problem and the transmission should work again.

 

[Quick6'n'-K.C.]

Good info-
the TV cable did have tension on it, but was really loose, it had 1/2 inch deflection each way from center line-

at the same time, the POSITIVE battery cable went bad, and i never got to ride in it till tonight- i diagnosed the POS cable, he put it on sunday, and now the car runs, but wont upshift-

on sat, i tightened the TV cable just like i would a buick, run it in toward the firewall, floor it, and let it ratchet out, then back one click-

so, i thought that would fix the trans issue, cause the cable does have tension on it in the trans....

LIMP MODE? got a link so i can read a little on it?

maybe the cable is snapped, it did spring back straight once the TV cable was tighter-

thanks for you help,
BW

 

[MeanBuicks]

Here's a very nice article on the TV system. A line pressure check will help you diagnose TV system maladies.

If all checks out with the TV system, consider checking the governor. It's located under the round, tin cover towards the rear of the transmission (on driver side.) The spool valve in the center of the governor shaft must move in unison with the weights in accordance with road speed. If the governor hangs due to a sticking valve, the transmission won't realize the vehicle is moving and the governor won't tell it to upshift.