Thats not the issue, the issue is a th400 needs 12v going to the kick down plug on the side of the trans to increase pressure to the clutches, a th350 has a mechanical link to the kick down. So if it had a 350 in it originally the 12v switch would not be on the accelerator pedal.
Ronnie, you’d want to use ‘all the pull’ of all three gears, so you’d want that to be right where the tach was when you did the 1-2 and 2-3 shift. Unless you have overdrive that’s not ideal for a street car because your trap speed becomes your top speed, but using a shorter tire is a cheap way to raise it some. Patrick
It was originally a 350/TH350 car and the kick down is not hooked up. I WILL look into this. Thanks Gary! Unfortunately I didn’t look at the tach when I went through the traps. I will be sure I do next time. I do know that I panicked a little on the 1-2 shift and shifted a bit early (4800) I just really didn’t want to over rev it. I needed to drive it home. Lol Cliff
AWESOME Going to the track and running your Buick is the most fun thing to do with it (at least to me) You have the bug now, get your wallet ready, like I said tho, its fun Its fun too if/when you go to a cruise in, you can be proud knowing you "run" your Buick at the track, to me that trumps loads of chrome and a thumping stereo!!
Can always wire a toggle switch for the kick down, even on the street if you turn it on the trans is waiting on YOU not a delay waiting for the trans. I ran that way for years. Johnny
A THM 400 will also short shift if left in Drive without the kick down hooked up. Looks as if you were shifting it yourself so it would not have been a factor.
You can put a simple micro switch on the throttle linkage at the carb. I used one designed for nitrous.....some people think I have nitrous when they see it....haha
I would assume 1 wire from switch to +battery, one from -battery to tranny, and 1 wire from tranny back to the switch? I learn new stuff on here all the time. Is this better than a toggle switch in the car, I mean is it only meant to be used under full throttle or can it be engaged at any time? Thanks Cliff
Go on a ‘test and tune’ day (bring it to the GS Nats!) and keep playing with shift points. My 455 is essentially stock and it likes 5300. Unless you have really tired valve springs 4800 is too early. When you find that sweet spot, move on to launch-see how much rpm you can get ‘up on the converter’ without breaking traction out of the hole. (I’m better at telling this than doing it, but the fun is in the try!) Patrick
If you wire 12 volts constant to the transmission, it won't shift except at full throttle. Why not hook it up right and then take the time to adjust the governor weights so that the transmission shifts WOT right where you want it to. When you shift the transmission yourself, the actual shift is accomplished differently than it would be if you left it in Drive and let it shift itself. My transmission builder told me it will wear on one of the bands which will eventually fail. I know lots of guys like to shift themselves, but I like setting the governor up right. One less thing to worry about, and it lets you look at other things like the gauges. I am sure a transmission can be built with the intention of self shifting it, besides the obvious manual valve body option.
I run automatic valve bodies on my race cars. Leave line in 2 and let 1-2 happen automatically, then manually shift the 2-3. Builds more line pressure and harder shift letting the 1-2 happen with indicator in 2 as opposed to D(3). Don't ask me why but I'm sure Mark Deconti knows. I'm still running the same T400 that he built for a raffle that I won at the GS Nationals in the 1990s!
Once you get the downshift worked out, and you want to grind the governor, I did an article with drawings that was published in the Dove Buick GS book. If you don't have one or access to one I can get you the info.We grind all our street Buicks governor to shift 5000-5200rpm. gary
Great information. Thanks! You guys are the best. I see mid to high 12's in my future. I may have questions when it gets to grinding the governor. Trannys are kind of a mystery to me. Cliff
This is the only place I see for a wire to be hooked up for the kickdown. Do I just need to run a wire from this to a switch then to battery + ? I’m guessing no negative wire is needed as the tranny is already grounded? Thanks Cliff
