That said, i have a question about the way my car makes the changes... I've recently swap the tranny in my car to a th-350. But it does the first change at 10mph, and the 2nd change at about 20-25mph, how can i make it do the change at a higher speed. I feel like i'm not getting the best of out of those gears. ((Automatic transmission)) Please help
If I'm just at part throttle, I get the 1-2 shift around 10-15mph also, give or take a couple mph. Under hard acceleration it's more like 45-50 for the 1-2. BTW, I also have a TH350 in my 68. Hard to judge by the MPH though, I have 2.56 posi rear, so my mph is high but rpms are low.
? Well the rest of the car is a v8-300 with a 4bb carb and of course the th350 i dont knwo what you mean by wide open throttle
Re: ? When I say wide open throttle, I mean is that where it shifts when you're running with your foot on the floor? or is it at partial throttle... when your foot is only giving it "cruising acceleration" pressure?
Re: ? Wide Open Throttle (also called WOT) is when you: 1) take your right foot and plant it on the gas till you hit the floor 2) try to press harder 3)leave it there :laugh: Literally, it's when the throttle is open 100%
always wide open I'm sure the throttle is always wide open when i'm driving :grin: But usually when i hit the gas really hard, it does the first change at 20mph and the second at 40mph but if i press the gas like a normal human then it does the first change at 15mph and second at 25mph is that normal?
Not knowing the 300 v8, but I'd venture to say that is way low on WOT. Under normal operation the upshifts are controlled by the vacuum modulator. It's a little cylinder on the side of the trans that has a vacuum line running from it to the intake manifold. Under WOT the upshifts are controlled by the governor. It is a shaft with a gear on the bottom to engage in the trans. It is housed on the passenger side of the trans under a "cupped" cover. At the top of the shaft are 2 flaps that are spring loaded. Under WOT the flaps begin to raise up and away from the shaft due to centifugal force. They (somehow) trigger a gear change. These flaps are modified by grinding weight off them. The springs are also swapped out. Kind of like recurving a distributor. I believe lighter weights and springs gives a later shift at a higher RPM.
I did the TH350 change over when my 2 speed blew with a 300 motor. It would shift to second at WOT around 35-37mph, third came around 85mph... but it doesn't sound like you'd be one wo bring it up to that under WOT. The result was the same with the 2 and 4 bbl intake setups. Yardley is also pushing you in the right direction, you might want to check that your vaccum is connected correctly AND giving the trans enough vacuum. Also check your detent (kick-down/passing gear) cable is correctly adjusted... I had issues with that. Oh, BTW: not that the shift point matters but it had a mild shift kit in it, and the 120mph speedo was often buried.
Marvin, If you just feather the gas, the trans should shift 1-2 at about 10 mph, and 2-3 at about 20 mph. If you floor the gas pedal from a stop, 1-2 should be about 40 mph or higher, and 2-3 about 70 mph or more. It depends on you rear gear. On the THM-350 trans, it is very important that the detent cable be hooked up and adjusted correctly. The cable originates on the front passenger side of the trans, above the pan flange. It attaches to the gas pedal on the other end. The trans recieves 3 inputs to determine correct shift speeds at different throttle angles. They come from Vacuum modulator(vacuum-engine load), governor(vehicle speed), and detent cable(throttle angle). All must be functioning properly for the trans to shift correctly.
