400 Tranny Kickdown

[skokie]

Ok this is weird. I put the truck in shop for a kickdown issue. With a carb mounted kickdown switch and a factory kickdown harness the tranny would kick down to passing gear but it would not shift back to 3rd from 2nd. The tranny guy is stumped. According to the assembly manual the orange wire goes to the tranny from the front spafe of the switch. The pink wire goes to the fuse box. Now for the weird part. If you unplug the power (pink wire) it will kick down and let go no problem. If you plug in the power it will hang in 2nd. Any thoughts? Tranny was rebuilt and they have gone through everything.

Thanks

[Robert1970C20rstbukt]

Maybe the kickdown switch is bad?

[COBALT]

...that's why earlier when you posted about this I told you to test the switch with a 12v probe tester. You have to isolate the switch as a problem before you can determine that the detent solenoid inside the transmission is bad.

Go back to your original thread and try what I suggested. If it turns out your switch is bad you'll at least know it's not the transmission, and you won't be forced to waste any more time.

[CHEVY & GMC FOREVER]

That was happening to me for a while then I just unpluged all of it and manually downshift into passing gear and back up to 3rd, that worked for me.

[skokie]

Cobalt. I forgot to update the thread. That was done and both switches checked out fine. I took it home last night and get this. If you unhook the kickdown switch it will kickdown at half WOT. Yes with no kickdown setup installed it will kickdown and go back into 3rd when you let off of it. Tranny shop is building a new one for me and it will be ready on tuesday at no charge. I figure while they are doing that I can put a new flexplate on there and maybe that will get rid of the vibration I was having.
Thanks for the help guys.

[dwaite72lnghrn]

One quick question is are you sure you have good full manifold vacuum 12" or better? The modulator could be keeping it in 2nd because it thinks you need the power.

[skokie]

Originally Posted by dwaite72lnghrn

One quick question is are you sure you have good full manifold vacuum 12" or better? The modulator could be keeping it in 2nd because it thinks you need the power.

Yep that was at 14 or 15 if I remember correctly.

[COBALT]

What do you mean "half WOT"? If you don't have power to the detent solenoid it shouldn't kick down at all.

So, you have full manifold vacuum, and there's no fluid in the modulator? It's working? If the modulator collapses I could understand why it would help to hang up the valve body. Are you getting transmission fluid in your manifold?

When they did the rebuild was a shift kit installed?

[skokie]

Yep at half or 2/3rd WOT it kicks down into passing gear. I verified this by disconnecting the the entire kickdown setup. I was like what!!!! There was a shift kit put into the tranny when they rebuilt it. Which manifold are you asking about?

[COBALT]

Your intake manifold. If the modulator is busted fluid can be sucked from the transmission through the busted diaphram in the modulator up into the intake manifold. Since the intake manifold provides full vacuum it wouldn't take long for transmission fluid to end up in your intake.

Shift kits can be funny. If they're not done right you can have ALL KINDS of grief with your valve body. I'd be questioning the hell out of the shop about how they installed the shift kit and whether or not they made any modifications to the new valve body and circuit for your transmission (drilling holes in specific places, or using different size ball bearings...that kind of thing...

[skokie]

No tranny fluid in the intake manifold. As far as the shift kit goes I said forget it on the new build just get me a correctly working tranny. Shift kit can go in later. I want to get this sucker on the ROAD!!!!!

[skokie]

Ok tranny guy called. He has put a new tranny in. He did not hook up the kickdown setup. He wants to wait for me to get there in order to do it. Replacement tranny is a total replacement. Only things he used from the old tranny was the drive and driven gear. I will let everyone know what happens.

Thanks for all the help.