Just got my new 455 and th400 running. I rebuilt the th400 myself, but how can I get it to down shift into 1st? While rolling on drive, 3rd gear down to like 25 miles per hour, and punch it, it only downshifts into 2nd. Why not down to first? How can this be fixed?
Valve body calibration. Most 400's won't go 3-1. The 70 BB would go to 1st gear from 35 MPH and down. I wish my transmission would do that.
Yeah, that's what Carl was telling me last night. He says his will hit 1st gear. I just thought it was my transmission. It is a 73 Pontiac TH400. My th350 use to slam into 1st. Now I miss that. Is there a particular kit that will allow me to recalibrate it? Ken, where are ya, more work for you!!
If you find a kit that will do that you let me know. One of the things that made the 70 Stage1 cars so lethal on the street was that 3-1 downshift.
My 69 BA tranny ALWAYS used to down shift to first when I punched it in drive. Only since I installed a B&M shift improver kit (the street version) does it now NOT downshift to first from 3rd while in drive. It sucks.
That is interesting Ken, because I never ran this tranny before rebuilding it, but installed the B&M shift improver kit. How would this upgrade stop it from downshifting 3-1?
Actually, I think I'm wrong. I think it was like that before I installed the kit. In any case, as long as I followed the directions, it shouldn't matter. I am pretty particular about stuff and I know I did exactly as the simple instructions said. But, I wonder if my kickdown switch still isn't working now that I think of it. The wire going to it was broken, so I resoldered it and also put a new connector on the end and re-connected it, but still no kickdown. o No: So my next step is to put a meter on the switch and make sure it is good. There's no real click heard with these switches, you just have to put a meter on them and see. After that, maybe I'll have kickdown again. I sure hope so. I know I used to when I first bought the car and then I noticed it didn't do it anymore years later but maybe it was because that wire came off. ou:
Attach a suitable length of wire to the + post of the battery, and run it down to the transmission. touch the wire to the vertical kick down connection on the transmission. You should hear a click emanating from the pan every time you touch the wire to the connector and remove it. If you hear the click, the problem is the gas pedal switch or the wiring between the gas pedal switch and the transmission. It is easy to troubleshoot that with a test light or meter. If you don't hear the click, the trouble is inside the pan, either the down shift solenoid, or the wiring inside the pan to the downshift solenoid.
Most THM400's have a part throttle kick down that isn't triggered by the gas pedal switch. It's hydraulic activated. At about 40 MPH, I can get a downshift to 2nd without even getting into the secondaries.
Ahh, then I shall investigate. Add one more item to the neverending list of things to fix. LOL. Yes, at part throttle, it will down shift without opening the secondaries. But if I punch it going 40 or 50, It does kick down to 2. Will check my switch out. So the verticle tab is for kickdown, and te horizontal one is for?? My plug is like a T almost
The horizontal one is for the Transmission controlled Spark advance system, or in the case of a switch pitch, the stator control contact. If you can get a kick down from 3-2 at 60 MPH, the electrical kick down is fine. If you want, you can also wire a push button or toggle switch across the plug for the gas pedal switch. If you hold that switch while you take off in 1st, the transmission will not shift out of 1st gear, so you can roll off a light and stay in first gear, then hammer it. That's a little trick I got from Mark DeConti.
Larry, My switch has only one tang. Not two. It is a horizontal tang. Always has been. There was a wire that went to it with a sealed round black hard plastic boot connector which slipped over this tang to seal it from the elements. I'm assuming this is still the same kickdown that we are talking about.
It should be. It is possible that someone turned it 90* and it appears horizontal. In any case, apply 12 volts to it and listen for a click.
Oh I see what you're saying. You're talking about the orientation of the spade itself, not that it is "pointing" horizontal or vertical. In any case, yes, it's just the one. I'll check it.
I'm saying that the spade itself is housed in a plug, and that someone might have installed the plug 90* off, not that it makes a bit of difference. That is your kick down contact, or it should be. For all you know, there is nothing connected to it on the inside of the pan. That is why I told you to apply 12 volts to it with a jumper wire to see if you hear the click. Start your trouble shooting there. It should take you all of 5 minutes.
My 71 BB downshifts 3-1. Would do it from 40 MPH when I tried 3.08 gears. There are different valves in the valve body of the BB and some parts left out as well. It shows this in the 70-71 service manuals exploded views. The Olds OW trans will do the same tricks.
So 70 and up BB Trans do the 3-1, but earlier years do a 3-2 shift? And the hydraulic kick down is controlled by? o No: My 69 BB Trans only kicks down when floored (foot pedal switch), doesn't kick down at part throttle like my old TH350 would do.
There are differences in individual valve bodies for different year and model THM400's. This article about switch pitch transmissions explains a lot of it. http://www.buickperformance.com/SPTrans.htm
