My trans has a B&M shift kit. Up shifting from low to second workss fine as long as my foot is into it. If i take my foot off, it automatically goes into drive even though my shifter is still in second. If I down shift frm third to second, the trany stays in drive. Normal driving in third, ****** is normal. Is this a valve body problem. Any advice would be greatly appreciated
might just be the way it's designed. There's a p***age in the valve body you can plug to prevent it? or use a different spool valve in one place, or grind the land down on it? been a while, though. I'd have to get out my TH400 book to remember
I have the 2nd gear kick down wired to a 2 way switch on my shifter. the other position is for the switch pitch converter, If I press the switch for the kigk down nothing happens until I put my foot into it. All very confusing. Thanks for replying.
it's supposed to kick down when you push the throttle down all the way. And not get power to the kickdown solenoid until you have your foot down all the way!
Its a recent developement, I have been driving the vehicle for 3 years with everthing working fine. I have been using the down shift for breaking in all gears, mostly second though. It quit all of a sudden. The ****** is 5 years old from rebuild. Thans for the reply.
Might want to start out with the whole story, instead of just a little part of it? intermediate band?
Reading between the lines on your first post, in normal driving in D, it shifts down as it is supposed to? I agree with Jim, the whole story would help. Do you have an adjustable modulator?
Without any more information, the path I would go down- there is 12V going to the detent solenoid when your 2-way switch is activated, modulator vacuum source good, modulator good and modulator spool free. Any further steps would involve going into the transmission.
I might be able to answer your question if it didn't have a shift kit in it. I really do not know how the shift kit has modified the shifting. On a stock 400, the shifts are all clutch to clutch. The shift kit might also apply the intermediate band in second, I don't know. The band is quite small and only there to give you engine braking in second gear. It is only applied when you select the 2 position on the shifter (stock valve body). When you place the shifter into any forward gear, the forward clutch is applied and remains applied in any forward gear. When the trans shifts to second, the intermediate clutch is applied giving you second gear. When you shift to high the direct clutch is applied (intermediate clutch stays applied) giving you high gear. If the intermediate clutch is slipping, it will appear that second gear is missed and the shift is first to high. When you really get on it, the transmission working pressure is raised and may make a clutch that is just starting to slip hold. My guess is that you have an intermediate clutch that is starting to go. There is one more part in the equation. The intermediate clutch has a one-way roller or sprag clutch which figures into the equation. In second gear, the intermediate clutch holds the sun gear stationary in the gear train. The one-way clutch is what allows you to keep the intermediate clutch applied when you shift to high. I guess it is possible that it is starting to fail and will only hold when you make a hard 1-2 shift. At any rate, the trans has to come apart to repair either one.
I would drop the pan and see what is there, you might find some orange plastic which would be part of the front ac***ulator piston. The original is plastic and they fail. The symptoms you describe fit that part failing. That is where I would start. And you would need to drop the valve body to replace it ( with an aluminum part )
If it is broken don't buy some piece of CHINA **** replacement, Buy a Sonnex part or a used GM ( I think they quit using plastic in 87 )
The Jalopy Journal
