th350 detent valve travel question

[Cliff Ruggles]

Setting a TV cable on a 700-R4, 4L60 or 200-4R is a completely different deal than setting up a TH350 kick-down.

On the OD transmissions line pressure is determined in part by throttle position, so it effects ALL aspects of shift function.

On the TH350 the cable only needs to be adjusted to completely apply the valve for forced heavy/full throttle downshifts.

If you mess up on your settings for the TH350 no harm done, it just may not work well or at all if you don't have it completely applying the valve the same time full throttle is reached.

If you botch setting the TV cable on your OD transmission you can "smoke" the clutches in short order as line pressure could be too low and it will "stack" up the shifts in situations where you want it holding them longer and with more pressure.

When setting the TV cables on OD units and you are looking for the best place to be, start out so the shifts are later and firmer instead of soft and early.  Then one notch at a time move the direction needed to get the shift timing and firmness where you want it.  Verify that you can still reach full throttle after the settings are made.  This is seldom a problem with factory set-ups as GM already figured on the cable mounting points and geometry from the carburetor linkage. 

Folks get into trouble with aftermarket carburetors and adjustable cables used for retrofitting OD transmissions into older vehicles.

Another big problem is setting up the transmissions to apply the TCC (Torque Converter Clutch).  I still see folks putting them on toggle switches so they have full control of the TCC.

The wiring to the TCC should be routed thru a vacuum switch hooked to ported vacuum then grounded on a normally "open" 4th gear pressure switch.  Options for that deal are to use a toggle switch and even a brake pedal switch before the vacuum switch, but they are really not needed.

Wired in that manner the TCC will only apply once the transmission reaches 4th gear, and ONLY when engine load is light or "normal" driving.  Any heavy/full throttle or coasting and the TCC will unlock just like it does with factory set-ups.

The method I use here to fix all those TCC issues is to install a non-LU valve in the VB and have a custom converter built that doesn't have a TCC.  Then we don't have to worry about how to apply the TCC effectively when we are retrofitting OD transmissions into older vehicles...........Cliff

[stevef]

Just adding some information that might help somebody else. I was thinking about what could cause the cable not to adjust correctly. I should have thought of this before, but it could be the intake manifold. It's an Edelbrock Performer intake (not RPM), that's supposed to be a direct replacement for the factory intake, and as far as I could tell it is. Everything fits, I'm using the original Q-jet carb, and the TA shaker fits to the hood very well. So, that's why I didn't consider that it would be the problem to begin with.

But, it has now occurred to me that the carburetor mounting pad on the Performer intake could be positioned slightly rearward of the original position of the factory intake. A small amount, like 1/4 to 1/2 inch, wouldn't be enough to notice much affect on the shaker fit, but it could be enough to throw off the detent cable adjustment. I haven't taken any measurements, or done any comparisons of the carb pad locations between the 2 intakes, so it's just a theory, but a very possible one.