General Category > Quadrajet Carb Talk and Tips

th350 detent valve travel question

(1/4) > >>

stevef:
I bought a rebuilt th350 for my 79 Trans Am with an Olds 403. The detent cable on these connects to the carb throttle linkage. So, I put in a new detent cable and adjusted it at the carb as I've done with my other cars before. When I first drove it, it didn't shift right. It didn't feel like it was hitting all gears. Also the kick-down only worked sporadically when I tried it. So, I disconnected the detent cable and it's been shifting in all gears fine now, without the cable connected. But, I want the kick-down to work, so I decided to drop the pan to see if I could see any reason that the detent wouldn't work right. The cable and connecting wire works freely, no sticking or binding. The detent valve isn't sticking. Before I put it back together and try again, I was wondering about the detent valve travel in relation to the kick-down activation.

I've noticed that detent valves normally push in with light spring pressure most of the way, but in about the last 1/3 of the travel the spring pressure becomes stiffer. My question is how much of the valve has to be pushed in for the kick-down to work? My valve is pushed in 2/3 of the way with the q-jet at WOT. It doesn't push the valve all the way in. Is that enough? Does that last stiffer 1/3 part of the travel play a role or not? Or is the action already done by the first 2/3 of travel? Or is the last 1/3 of travel where it kicks in? If that's so, any ideas how I can get the cable to pull that last part of the travel. Thanks!

tayto:
How did you adjust the cable? Also, have you verified that when press the gas pedal all the way that the carb opens all the way? I have seen LOTS of gm cars where this does not happen!

stevef:
Adjustment procedure is: With the q-jet off fast idle, un-lock the snap-lock button, move the throttle lever to wide open, and lock the snap-lock button.

It is possible the gas pedal doesn't move the throttle completely wide open. I'll have to look at that. But I haven't found my other cars to be that particular about being fully WOT for the kick-down to work. But, I will check it.

Still wondering how much of the detent valve has to be depressed for it to work though.

Thanks!

Cliff Ruggles:
The cable on a TH350 is not a player in shift function in the "normal" driving range.  It is for forced heavy/full throttle downshifts so shouldn't come into play until pretty late in the travel of the throttle.......Cliff

tayto:
Is it aftermarket cable or AC delco? i have not had good luck with aftermarket TV cables for the 2004R/700R4s. Ac delco ones are the one to use IMO.

Navigation

[0] Message Index

[#] Next page