[Madmax305]

I had a 700R4 put in my 67 Elky about 6 months ago. It drives great, but for the last couple of days I noticed that it is downshifting really hard,(slamming), into first gear as I roll up to a red light. The trans shop adjusted the TV cable after they installed the tranny. It has about 500 miles on it and I have never abused the car/transmission. Should I have any concerns? Any thoughts?

 

[Chevelle '71]

Sounds like your line pressure may be too high...? The governor controls shift timing and the throttle valve controls the line pressure which translates to shift feel. Are your upshifts harsh as well..?

 

[Robinls5]

I have a 700 behind my 468 in my 70 Wagon. The only time mine shifts a little hard going down is when I have it in third. When the cable is adjusted ---Very close--- It should up shift close to -- 13-- 36--55 MPH.
Your cable should be mounted to the carb. pointing to the rear at 58 degrees and the piece that the TV cable snaps onto at the carb should be close to --1 and 1/8" from the center line of the throttle shaft.
The piece with the square hole in it should be-- From the front of the square hole to the center line of the piece that mounts on the carb and looks like a " Nail Head " . Should be very close to 4 & 3/4". ( engine off throttle relaxed).
If all measurements are correct-- Slide the TV cable to towards the firewall, NOW very SLOW, From inside your car, PUSH down SLOW and listen,,,,, If you hear a CLICKING sound the TV cable is setting itself.
WHERE did I get these measurements. I found a G.M. engine at a bone yard........... Got the yardstick and a crayon and did mine like the factory.
My 700R4 has around 40.000 miles on it. My 700R4 is out of a 454 mid eightys Suburban
PS.-- Oh, Did I mention,,, I drove my first 700R for about a half hour with the TV cable " Out of adjustment " ,, Total destruction of that transmission. Then I did my homework. This trans. has been just fine for nine years. So I believe ( Due to nine years and NO problems ) I think I got it RIGHT.
Bob

 

[Madmax305]

Sounds like your line pressure may be too high...? The governor controls shift timing and the throttle valve controls the line pressure which translates to shift feel. Are your upshifts harsh as well..?

Up shifts are firm but not harsh. I have the Lokar transmission cable set up, it is not self adjusting. It only down shifts harsh when it goes back into first gear. I always drive it in the 3 speed mode while city driving.

 

[Chevelle '71]

Up shifts are firm but not harsh. I have the Lokar transmission cable set up, it is not self adjusting. It only down shifts harsh when it goes back into first gear. I always drive it in the 3 speed mode while city driving.

Okay. Bummer that you do not have any adjustment on the cable, you could just follow steps noted in previous comment. On some early models the transmission can go max pressure if the TV cable slips or breaks. This was like an early version of limp mode to get you home without smoking the trans. You can reset this at home. Car off, check if TV cable has tension on it, which it should. When you disconnect it, it should retract towards fire wall. If not the cable is too loose, this will cause line pressure to be too low also resulting in clutch slippage. You should have around min 70psi line pressure at idle and 150/180psi at wide open throttle. I like to set them a little firm to be on the safe side. There needs to be some way for you to adjust the cable...

 

[Madmax305]

The cable is adjustable, it has a barrel nut with a set screw. Right now, the cable is tight as a piano wire....

 

[Chevelle '71]

The cable is adjustable, it has a barrel nut with a set screw. Right now, the cable is tight as a piano wire....

is it limiting accelerator stroke prohibiting wide open throttle?

 

[LeoP]

sometimes the trans's will skip shift on the way down.

 

[Madmax305]

UPDATE. I rechecked the TV cable and it was loose, I tightened it and test drove it. It up shift/down shifts perfect. Thanks for all the replies guys....