Hi all,
Any thoughts on the following?

I've been trying to get my passing gear (kickdown) working.
1974 350 with original TH400.

I've replaced (and set) the throttle switch and wiring to the transmission.

I've dropped the sump off the TH400, checked the solenoid and valve chest (I've stripped cleaned and rebuilt the valves - although they didn't really need it).

The kickdown circuit works fine (It throws the solenoid when my right foot is planted).

BUT: No passing gear

Looking at Ron Session's book and the circuit pressure diagrams I guess the other bits that can effect this are the vacuum modulator (new) and the valve, which I've checked and seems fine. Yes I've got good vacuum too. (And the ATF level is correct).

So what next ??????
Is the BOOST/Pressure Regulator a possibility ?
I'm guessng if the line pressure is low (ie. the regulator is stuck open) then there might not be enough pressure to force the dentent circuit into life ??

Any other thoughts (I don't have a pressure gauge and so haven't measured anything) - just trying to fix this problem blind.

Advice / thoughts / hints - all welcome.

Jeremy (UK).

 

Jeremy,

Here's a check, and I know you have said you did some of these things, but re-check and follow these instructions. (print them out)

Look to see if the hose is off the vacuum line that goes from the intake manifold to the line, and from there on down to the transmission, (are the hoses crack free also). Down there is another hose that connects it to the vacuum modulator. It must have this hose on all the way, and in good working order (cracked hose or bent) or your shift will be messed up.
There is a kick down cable that runs from the linkage on the carburetor that works passing gear, and goes to a lever on the side of the transmission. When the throttle is wide open, the cable must be pulled all the way, and without binding. If it is, then you must adjust it. If you don't know how to adjust it, then find someone that does, because it is hard to explain how to do it due to how the release on the cable works.
The modulator controls the shift points, so if its getting vacuum, and no fliud runs out of the hose when you un-plug it at the modulator, it's probably ok. If fluid runs out of it when you un-plug the hose, then you have a bad modulator. (new or not check) The one you have may need adjusted. When you remove the hose at the modulator valve, if you look up inside the tube where the hose plugs on to, you will see a screw. This is the adjusting screw, you may need to turn it one way or the other to get it working to where the transmission is shifting normally at 15-20 and 34-37 mph, but always count the number of turns you go, so you can get back to where it was if that doesn't resolve the issue.
The governor also controls the shift, and it may be sticking, or bad (even new ones) You will see a cup looking thing that sticks out on the drivers side of the tranny, and it usually has a big spring that clamps it in position. This is where I'm going to tell you to go to a transmission shop to have that worked on unless you know about it and how to take it out and clean it good with carburetor cleaner. Hold it up by the gear, and press the weights in, you should see a valve inside through some slots in the side, if the valve is not moving, then either you must replace it, or clean it with that carb cleaner and air pressue (no rags) until it works.
Are the springs off the weights, or missing ?. It should fall open each time you let go of the weights. My other guess would be someone put a manual valve body in it and the governor is sticking. The modulator controls where the shift takes place, and the governor make the shift happen when they sling outward moving the valve inside the governor. They are bad to stick and must be clean in order to work right. Is yoyr shifter installed right ?. Does it move the arm on the side of the transmission into each click as you move the shifter ? have someone move the shifter through each gear while you watch the arm. Move the shifter and transmission into neutral. Take the cable loose, and make sure the transmission is in fact in neutral position. Moving it in the direction of 1st gear, go all the way, and move it back to each click. Two clicks ought to be neutral, now move the shifter to neutral on the indicator in the car. Tighten it down and you should now have all gears, but make sure it puts it all the way into park, or you will have a problem with it jumping out of park.

Sorry for the long check list, but your issue is in one of the above. (and any spelling errors) This tune up cost big dollars at a transmission shop and all above is for either TH350 or TH400 transmissions
Good Luck

 

You say it "actuated" the kickdown solenoid. Does that mean you know for sure that the solenoid valve opened when it actuated? Or do you only know that it made noise? The solenoid valve can be damaged or plugged with debris so that it 'actuates' but doesn't really OPERATE. [Those kickdown solenoids are notorious for being cheap and failing in numerous ways.]

 

7T1 -Thanks, I took the can off the solenoid and cleaned all the sludge out of it. (It's the oval can style) put a new aluminum washer under it at rebuild. The base with the bleed hole is in nice and tight. I've pressure tested the solenoid (by blowing hard into the bleed oriface). I can blow through it with 12v applied and not when no voltage. The needle valve moves up and down happily with voltage - so as best as I can say - it works. If it was leaking it would be in passing gear the whole time - whereas it never gets into passing gear.

To answer some of the other points raised:
I hold a steady manifold vacuum of 18" and this wouldn't be the case if the vacuum modulator was disconnected or leaking. (And the modulator and connecting pipe are new - I swapped out the old ones incase)

The TV cable that GA refers to is only applicable to the TH350, whereas the TH400 is electrically operated. And as far as I can tell this system is working properly. (I take your point 7T1, but I believe it works).

Thanks for the Govenor info. I am aware of testing it and what it does, but since the trans. is in the car I can't get it out easily to test it. I have NO other problems with the gear changes (up or down) so I'm guessing the govenor is OK. - But I know it could be that.

Any other gurus ?
Could it be the pressure regulator valve ?
I'm really hoping to fix this problem with the trans. still on the car!
Although I expect to be beaten.

7T1 - I think that swapping the solenoid anyway may be my next step.

Thanks,
Jeremy

 

Thanks to everyone who has looked at this thread.

Is there a recognised transmission guru on these forums ?

Jeremy.

 

Jeremy, thought I would ask the obvious first. You know it won't kick down at high speeds. There is a certain point where the electronic kick down no longer kicks down - that is how it was designed. Have you tried cruising at 60k's (in top gear) and sticking the boot in?

A often symptom of no downshift problems is also early or late upshifts, no upshift, 1-2 upshift at wide open throttle only. Do you have any of these symptoms?

Cheers,

P

 

P,
From a standing start, boot on the floor:
1 to 2 at redline (5300 ish)
2 to 3 at 4000 revs

With a much more gentile approach to the throttle, both 1/2 & 2/3 occur at around 3000 revs.

Don't know if that answers your question?
Jeremy.