I just swapped a TPI system onto a carbureted engine. I also installed a brand new TV cable (from GM) and used the stock throttle bracket and throttle body. I say this to let you know that the geometry is all correct. The cable was adjusted just as the factory service manual instructs. The fluid lost during the TV cable swap was replaced with new fluid.

Immediately the transmission began slipping. 1st to 2nd sometimes hangs, but 3rd has problems. There's also a metallic noise during shifts. Making further adjustments to the TV cable has not improved this condition.

What could have happened? Is there something else internally that should have been replaced? I know the TV cable moves the TV plunger against the TV spring (internally). Is there anything specific to the stock TPI transmission internals (like the plunger, bushing, spring, or valve?

Sound like an unfortunate coincidence. If the geometry is correct, and the tv cable is for a carb and it is adjusted properly, there is not alot more you could have done.

I think I read it backwards. Regardless, if the correct tv cable was used it should have worked.

Thanks for the reply.

I've been thinking the same thing...that it should have worked without any problems. I'm still curious to know if there is anything different about the stock TPI transmissions?

To my knowledge, no. tv parts inside the trans are the same. There are aftermarket tv springand tv links. They are one size fits all. The gm parts are only available when purchasing the complete valvebody. Most valve bodies are discontinued anyhow. This makes confirming tv part differences nearly impossible. I can say that all the tv pieces appear the same, regardless of which unit I have apart.

I think its the increase in torque from switching to TPI. now your motor has enough power to start slipping the trans.

Thanks

We've intentionally not put much power through the transmission until the shifting feels good.

There are indeed many many variations fo 700 trans in our cars.

Anyone who doubts this can verify it by loking at a factory manual and all the applicable service/part numbers available for the valve bodies alone. Each one is calibrated to the engine and gear ratio originally in the car.

The TV link pin from the cable to the actual throttle valve in the trans is always suspect. Quite a few variations in that alone.

Believe it was the 89-91 model 700's behind the 350 TPI that had a longer than spec tv pin and would hold up fine in stock apps. The minute u did more than put an exhaust on, they trans would tend to let go with any power increase whatsoever. Only way u can tell them apart is to have them side by side to compare.

Or none of this influenced anything and it was just its time to go :-)

later
JEremy

Is there anything special I should know about getting the transmission rebuilt? I don't want to assume that the guy rebuilding the tranny knows everything.

Thanks

Interesting that I found this old thread. I have the same problem. I have to pull the TV cable extra tight so that shifting work right, but then the TV bottoms out when I am at 80% throttle. It's almost to be expected. A Quadrajet has a very small throttle (primaries) compared to the TPI butterflies. So the initial throttle movement makes more torque even without differences in induction type.

My temporary fix is a bracket I made which attaches to the throttle linkage essentially bringing the TV cable attachment point closer to the pivot point (i.e. reducing the radius). This works well enough that the tranny isn't slipping through shifts, but I am still looking for a long-term approach.

I contacted Bowtie overdrives about this and have gotten no response.

I am still suspicious that a trans behind TPI has a different throttle valve in the valve body than a trans behind a Q-Jet does. The torque vs. throttle angle is very different, so how can the some circuit in the trans work for both?

I found this idea at http://www.700raptor.com/:

"700R4 Throttle Valve Cable Corrector Spring. This spring will allow you to turn the pressure up and still be able to open the throttle wide open. "



I was thinking about rigging something like this up to give it a try. I have been trying to get it to "feel" like it was before, but I suppose I should really be using a transmission pressure gauge.