I'm having problems with my tranny kickdown.... I put an 89 tbi 350 out of a 3/4 ton burbun in my 79 3/4 pickup a few months ago. I hooked the vacum from the tranny onto a hookup at the back of the mainifold. and the kickdown has worked perfect until a couple days ago I put a tbi spacer and now it doesnt work... there is another port on the peice I hooked the kickdown to that had a hose hooked up to it that wasnt't going anywhere and causing a vacum leak. I cant figure out where this hose goes. I plugged the port and got rid of the leak but it still wont downshift when I punh it so I need to figure out where this hose goes

thanks
josh

that vacuum hose isn't the kickdown, it just tells the tranny when to shift. TH400 uses a electric kickdown, look on the drivers side of the tranny and you will see a electrical connection. Factory 400 trucks have the kickdown mounted on the inside firewall, somewhere near the gas pedal. Hit a certain position in the pedal, kicks the tranny to passing gear.

Definately true, some years they had a sensor on the carb instead of the pedal. You should be able to trace the wire off the side of the tranny back to where ever.

wow I always figured it was that vacum thanks alot guys

yeah if you're not getting vacumm you'll know it, the tranny won't shift.

-Scott

Originally posted by Cahdealme
some years they had a sensor on the carb instead of the pedal.

Cadillac was big on this method

but in a nut shel you should have a switch thats sends 12 to the trany about a hiar before WOT

okay the wire seems fine. but still no kickdown. I belive this other vacum port needs to lead somewhere. the thing I have my tranny hooked to sticks up about 2 inches out of the manifold and has a nipple on the very top(where the tranny is hooked up) and one halfway up that had about a foot long hose hooked to it.. I cant figger out where this hose goes. right now I have the nipple capped off and dont seem to have any vacum leak but the hose obviously went to something. I had no problems for the past 3 months till now when I put the spacer on.

please help
thanks josh

ok you see this switch when you hit wide open throttle it closes the loop sending 12 to the trany kickdown

http://buickperformance.com/TH400downshift.jpg

another pic of the switch

http://www.supercarsunlimited.com/electric/34308.jpg

ok now if you look where the pan meets the case ther is that roud thing sticking out form the trany with a nipple for a hose. that conects to a hose that goes to the back of the intake manafold (the 400 used manafold vacume)

http://peter.runestig.com/images/OldsRen24.jpg

okay I know about the electric kickdown and the vacum hose that goes to the tranny.. my question is where the hell the other vacum hose is suposed to hook up to

Originally posted by joshfj40
okay I know about the electric kickdown and the vacum hose that goes to the tranny.. my question is where the hell the other vacum hose is suposed to hook up to

what other vacume hose?

Originally posted by Chief yelling alot


what other vacume hose?

I'll try to get a pic today this is really pissing me off.
thanks for the help

Originally posted by joshfj40


I'll try to get a pic today

good plan ;)