hey guys, so I just finished installing a new speedo and gears into my car along with a new throttle body, torque arm bushing, and trans mount, I put a 37 tooth driven gear in to go with the 17 tooth drive gear on the tail shaft.

On its maiden voyage I was amazed at how much better it ran due to the new throttle body and happy to finally have a working speedo again after a year of not having one, and then I noticed how it shifted..

The trans would try to shift, hang there after its shift and then drop the rpms way low and then it'd chug. I thought my one year old rebuilt 700r4 just bit the dust which would of made a part of me die a little inside. after a bunch of rechecking everything I decided to unplug the new speedo and take it for a drive, problem solved.

Here's my theory, I have the wrong driven gear causing the computer to misread the speed and put it into lockup at a weird time. Does this seem plausible?

Also when I selected the 37 tooth driven gear I did a bunch of online calculations and calculators and that's what I ended up with. What would you guys recommend for 26inch tire diameter and a 2.77 rear?

 

Part throttle shifts are controlled by the throttle valve cable & governor.

Speedo gears are driven by the output shaft in the 700-R4. No way for the speedo gears to impact shifting.

VSS is one of the inputs for lock-up speed by the ECM.

Unplugging the TCC wiring at the trans. for short-term drivability testing is a great way to determine if a TCC solenoid is bad. But it's more likely that you just tooled around with the throttle body and your throttle valve cable is not connected or very mis-adjusted.

An early third gen with 2.73 rear, TH200-C and tires around that height could have had 17 / 37 or 17 / 38 speedo gears. What I'm saying is you're close enough that driveability issues aren't coming from the speedo gear ratio.

 

I know how to set TV cables and did so after I put the new throttle body on so I don't think that's the problem. It was as if the trans was shifting at the right points but after the shift it would drop a little bit and then drop even more and have a slight chug. I never ran lockup on this trans until yesterday due to not having the correct speed sensor, I'm really confused now, all the problems stopped ones I unplugged the speed sensor pigtail

Edit: also it seemed as if the speedo was reading pretty high

 

You may need to set minimum air / IAC.
https://www.thirdgen.org/forums/tech...ml#post1304610

Post-shift rpm drop shouldn't be a noticeable issue on an automatic car. With a stick car, not having a VSS signal to the ECM will cause the engine to drop way low and stall when not in gear.

 

I'll recheck it tomorrow morning, it's possible I could have did it too fast in a rush to hear the car run with the new throttle body, you think that could be a possible cause for what I'm experiencing even with it running fine without the vss hooked up?