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This has maybe been done or asked a hundred times. But how to adjust or fix the turbo 400 kick down switch. My 70 SX had a 256 posi gear from factory. It now has a 10bolt posi 308 gear. It does not down shift unless im going real slow. My 70 442 has a 323 rear from factory and still has that rear and will not shift from first to second unless i remove petal from floor till 3/4 to 7/8 throttle? Is there adjustment or has to be ordered per gear or ? Please advise?
The kickdown switch is basically a switched connection to the trans providing 12v at WOT. You can make it adjustable to come in earlier, with some creativity.
The way you are describing that it sounds like you might have a vacuum problem make sure the metal line is plugged all the way into the manifold or there could be a carbon build up in the manifold end if a paper clip will easily go into the end of steel vacuum line its OK. if not you'll need to clean it out just clip a peace of the paper clip off and the clip will be sharp enough to twist into the hole and clean it out.and then make sure vacuum line is properly in modulator.. Its an easy simple and cheep check and fix..
If your vacum line plugs into the bace of the carbarator its more likley to have a carbon build up.. If it plugs into the side of carberator the rubber hose could suck flat while motor is running.
I had this happen on one years ago and it was two things. One was the vacuum issue like already mentioned. The other was I had no power going to the kick down switch. The trans only kicked down due to pressures in it. So, first using a test light make sure you are actually getting power to the kick down switch and threw it at open throttle. I would check it at the switch and at the connection on the trans. If that is all working maybe it is working correctly just not as you want. A way to make it come on sooner is to take a piece of hose about an inch long that fits over the shaft of the switch, slide it on the switch and it will make it actuate sooner.
Hope this helps.
As mentioned the rubber hose is one way, an adjustable bracket is another. You can change the location with a different switch to the carb, or you can make a finger operated switch on the shifter. Like I said it's looking for 12v at the trans, how it operates is up to you.
As mentioned the rubber hose is one way, an adjustable bracket is another. You can change the location with a different switch to the carb, or you can make a finger operated switch on the shifter. Like I said it's looking for 12v at the trans, how it operates is up to you.
So the button sends the 12v to the trans. And by the looks of it I got the switch that mounts on the gas pedal
Where does the kickdown switch mount to I seen somewhere it mounts on the carb? And how does it work?
The factory did this in different ways, depending on the model and year. The 1964 cars had a switch mounted to the intake that was activated by the carb linkage. Mid-60s cars had the switch integrated into the accelerator linkage bellcrank on the firewall. The 1968-up cars used a switch mounted above the accelerator pedal under the dash. As noted above, all you need is a way to close a switch and provide +12V to the kickdown solenoid at wide open throttle. There are a million different ways to do this.
I'm still mocking up all my 455/400 bracketry for '77 B-body.
I have been using an "intake-mounted" B&M TH400 kickdown switch. It usually fits pretty good (with washers) in the stock TH-350 throttle cable bracket hole (just below the accelerator cable) on my born-with-small-block cars.
I think I'd rather keep this setup than try to retrofit an OEM gas pedal-mounted solution. I wouldn't mind my intake-mounted switch to look more OEM, however.
Will someone please provide a picture of the 1964 kickdown setup JoeP describes? Is this item available for purchase?
Besides 1964 - did Oldsmobile ever produce a factory car with the 400 kickdown switch in any location OTHER than under the gas pedal?
Originally Posted by joe_padavano
The factory did this in different ways, depending on the model and year. The 1964 cars had a switch mounted to the intake that was activated by the carb linkage. Mid-60s cars had the switch integrated into the accelerator linkage bellcrank on the firewall. The 1968-up cars used a switch mounted above the accelerator pedal under the dash. As noted above, all you need is a way to close a switch and provide +12V to the kickdown solenoid at wide open throttle. There are a million different ways to do this.
Last edited by ReallyWildStuff; August 21st, 2017 at 07:20 AM.
Reason: unclear
What I don't understand is your reluctance to simply use the factory style switch on the accelerator. The 1977-1984 B/C-body cars used an accelerator pedal switch to cut out the A/C compressor at W.O.T. This bolts onto your car (you may already have one) and can be used as the kickdown switch. The only issue is that this switch opens at W.O.T. so you'll need a relay to reverse that and provide power at W.O.T. to the kickdown.
I just didn't make the connection between the similar functionality of the A/C cutout switch and the TH400 kickdown switch.
Yes I suspect the 77 Pace Car has an A/C cutout switch under the accelerator. Yes what you describe can probably be done cleaner than the B&M setup provides.
Its nice to have options, because I'm having some problems re-mounting the B&M unit because I'm trying to use all stock plumbing.
The 403 carb bracket for mounting the accelerator cable & kickdown cable/switch is much larger (extends farther back) than the 307 unit I had been using - and the B&M kickdown switch won't fit with the 403 bracket (interferes with the HEI distributor).
The B&M 400 switch now also will not fit with the 307 bracket when I additionally try to use the factory 403 carb-to-booster line.
Okay, my situation is a little different. I just did a power train upgrade to my 69 Cutlass S, swapped 350 and TH350 for a 455 and TH400. My car already had the kickdown switch mounted to the accelerator pedal bracket and the wiring to the TH400. But, I can't get the bar the pedal is mounted to to reach the kickdown switch. Even if I push the pedal to the floor, I don't contact the switch. Does this mean that I need to bend this rod, straighten the mounting bracket to raise the kick down switch closer to the throttle bar (part where throttle cable attached), or am I missing a piece of the bracket or hardware? I really don't want to spend the cash for a B&M or similar carb mounted setup if I don't have to.
I appreciate any help you guys might be able to provide.
Okay, my situation is a little different. I just did a power train upgrade to my 69 Cutlass S, swapped 350 and TH350 for a 455 and TH400. My car already had the kickdown switch mounted to the accelerator pedal bracket and the wiring to the TH400. But, I can't get the bar the pedal is mounted to to reach the kickdown switch. Even if I push the pedal to the floor, I don't contact the switch. Does this mean that I need to bend this rod, straighten the mounting bracket to raise the kick down switch closer to the throttle bar (part where throttle cable attached), or am I missing a piece of the bracket or hardware? I really don't want to spend the cash for a B&M or similar carb mounted setup if I don't have to.
I appreciate any help you guys might be able to provide.
A photo would help. I assume you have changed the accelerator pedal from the TH350 configuration to one for the TH400, correct? The pedal assemblies are different and you cannot use a TH350 pedal with the switch for the TH400. The TH350 pedal has an extra tab that interferes with the mounting of the switch for the TH400. This photo shows the extra tab on the TH350 pedal assembly.
You can remove the TH350 kickdown cable tab. It’s spot welded to the throttle lever, clamp it in a vise, grab the tab with some visegrips, wiggle it a few times and chances are it will break off.
There should be power on one wire with the key on, I think it’s on the gauges fuse. I don’t have my manual handy to verify the fuse or color wire. The wire that goes to the transmission is orange. All the 69 cars got the kickdown switch wiring as part of the dash harness, you will need to add the wire under the hood in the engine wiring harness. Once again, with out my manual I can’t tell you which connector body cavity the series 56 male terminal need to go in.
Thanks for the info Joe and Matt. I did get a new engine harness that included the wire to the transmission connector. Here's a couple pics of my switch installed on the bracket. My issue is the distance between the switch lever and the throttle pedal rod. Does the switch lever need to travel to the stop to close the circuit to the trans kickdown solenoid?
Your problem is obvious. The broken throttle cable with the screw fitting on it isn't adjusted properly, so the pedal isn't traveling as far as it should. I'm also betting that this cable isn't letting your carb open fully either.
Thanks, Joe. I did test the carb operation yesterday while driving and I am getting the secondaries to kick-in when I punch the pedal. But, now that you brought the throttle cable length to my attention, I see that is too short. I guess I'll have to buy a new throttle cable to allow for correct positioning of the pedal.
Thanks, Joe. I did test the carb operation yesterday while driving and I am getting the secondaries to kick-in when I punch the pedal. But, now that you brought the throttle cable length to my attention, I see that is too short. I guess I'll have to buy a new throttle cable to allow for correct positioning of the pedal.
The fact that the secondaries open doesn't mean that they are opening all the way. The only way to verify that is to have someone floor the pedal while you look at the linkage on the side of the carb that operates the secondary throttle plates (and don't confuse those with the air valves on top).
Your problem is obvious. The broken throttle cable with the screw fitting on it isn't adjusted properly, so the pedal isn't traveling as far as it should. I'm also betting that this cable isn't letting your carb open fully either.
Joe, I disconnected my throttle cable so that I could freely move the throttle pedal. But, even with the pedal fully pressed to the floor it barely engages the kick down switch. Any recommendations?
If your throttle cable was too tight you may have bent the pedal arm. They bend easily, you can just bend the top portion a little so it actuates the switch sooner. Once done, get a new throttle cable that allows full travel.
If you can get WOT at the carb, and the throttle returns to idle correctly, that’s about all you can ask for. If you can’t adjust the switch then put a small hose clamp on the switch. Position the clamp so the threaded part of the clamp contacts the throttle lever.
Thanks, ach1992880 and Matt for the suggestions. I just got a new throttle cable correct for my year/model and will either bend pedal arm or try the hose clamp trick to get proper activation of the kick down switch.
November 21st, 2012, 03:35 PM
Understanding T400 Transmission Kickdown Switch
