200-4r with D5 converter in a 1973 Century behind a 455 with small RV camshaft. "Built" transmission with transgo kit, red alto, wide band, billet servo etc etc. The 1973 7043240 Quadrajet, of course, has the Everyday Performance LLC TV cable conversion arm and a stock (+) calibration. The transmission had shifted perfectly behind a dual quadrajet 430 engine. That engine was sold, and the 1973 455 installed. On initial driving after the 455 install, the shifts were held off too long and were too harsh. Ok I thought. With the single carb I am using twice the throttle angle as compared to the dual quad engine, in the primaries. Therefore the tv cable is being pulled further so the shifting makes sense. But it didnt sit well in my head. The shifts were too harsh, holding off uncomfortably long. On further investigation, I found my initial timing at about 8degrees btdc. This on a low compression 1973 engine. Also there was no vacuum advance hooked up. I adjusted the timing to about 13initial, added vacuum advance, and what a difference it made. The additional initial timing let me close the throttle at idle, and with the vacuum advance made the engine run so much better that I need less throttle when driving in the primaries. This in turn has lessened the tv cable pull, thus softening and shortening the shifts. It drives great. The moral of the story is interconnectedness. Carb, distributor, engine, transmission. They work together as a complete system, and should be tuned as such. Often times a symptom is blamed on a component that is not the culprit. Look at the whole system when troubleshooting.
Yes, it's amazing how many transmission problems that came into the shop were actually engine problems like misfires or low fuel pressure.
Seems logical, if the power plant isn't making power in the right rpm range then everything else is going to be off including the hydraulic machine that transmits power to the wheels. It is too easy to forget the literal meaning of things (drive train components) and go off the rails in diagnosis. This was a good read. Thanks.
