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Discussion Starter #1
Recent home rebuild, standard automatic valve body
In Drive - stuck in 1st. Will not shift to 2nd unless I pull down to L1 and back to L2
In L1 - drives fine
L1 to L2 - Will shift into 2nd and drive fine
L2 to D - Will not engage 3rd. Stays in 2nd
P and N fine
R drives fine

Air checks during assembly seemed fine. Clutch packs engaging.

Kick down solenoid checked prior to install (applied 12v and heard relay clicking... other possible failure mode here?). Currently not connected in the car (no wire connected).

Linkage adjustment fine

Fluid level fine. Full mark verified.

Going to check modulator, vacuum signal,, and then governor. Mind you this transmission would shift VERY early prior to rebuild and in D would hit 3rd before crossing an intersection. I have not calibrated the governor yet, just reinstalled as is.

If that yields nothing, I guess I will get a pressure gauge connected (do not have one at the moment), see what I have, and lastly pull the valve body if necessary.

Anything else I should be looking at?
 

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Discussion Starter #2
Modulator and governor check out okay. Disassembled the governor and cleaned it up. Test drive tomorrow.
 

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Discussion Starter #3
Update....

Took it up and down the street today and under light throttle in Drive (D) it is shifting into 2nd at about 4k and I think it may have hit 3rd but I was going too fast on my street. Need to get on the open road where I can go faster and put a load on it.

Anyway, this was repeatable so I am happy it is shifting. The 1-2 manual shift (L1-L2) and 1-2 auto shift (D) are crisp and very quick as I had hoped. Just need to figure out why its late.. Again, I have done nothing to change the shift points.

Here is what was done...

Modulator - was a little hard to get out. Seems to stick when fully seated but moves free otherwise. No sure if its a liquid suction or if its actually binding. Scotch brited the valve, cleaned, reinstalled. Modulator screw backed all the way out flush with vac fitting.

Governor - valve seemed sticky so I fully disassembled, scotch brighter, cleaned, assembled, and reinstalled.

Possibilities...
1 - detent is failed in an energized state (despite no 12v)
2 - modulator actually sticking or not enough vacuum (7 psi now, had 11 psi on dyno... needs more tuning)
3 - shift valves? Thinking it unlikely that the 1-2 and 2-3 valves are both stuck or would cause the symptoms I have.
 

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This sounds like either lack of vacuum (leak) to the modulator or a the modulator itself issue. It's cheap to replace.
 

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If it's a TH350, sticking kickdown cable. If a TH400, a leak at the kickdown solenoid or a piece of trash keeping the valve from going fully closed.
 

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Discussion Starter #6
If it's a TH350, sticking kickdown cable. If a TH400, a leak at the kickdown solenoid or a piece of trash keeping the valve from going fully closed.
TH400 as noted in the title. When de-energized (no 12v connected), is the valve supposed to be open or closed? How can I determine what state it is in?

I dont really understand the solenoid operation other than its energized when you lay into the gas pedal. What does it physically do where it attaches to the case? The solenoid appears to have a diaphragm on the face that mates to the case but no passages or anything. The relay clicked and moved freely when I tested it prior to assembly.

This sounds like either lack of vacuum (leak) to the modulator or a the modulator itself issue. It's cheap to replace.
No vacuum leaks that I can find although the engine vacuum is a little low relative to what I had on the dyno (7 vs 11). Hard line from manifold to modulator with a short rubber line at each end.
Modulator is good, no leaks in diaphragm. However, as I stated above, the modulator valve (in the case) might be sticking when fully inserted into the case? I cant tell if it is sticking or if it is appearing to stick due to liquid suction when trying to pull it out (eg. like stepping into deep mud an losing your shoe when pulling your foot out... I don't know how else to explain it). It inserts easily, sticks when you remove it. I don't have another transmission to compare it to.

I should have it out on the road Monday for a little more testing after I get the front end back together.
-Kevin
 

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Kickdown on a 400 happens when the solenoid is energized and it is getting 12v. The valve in the center opens and fluid is dumped from the passage that is normally blocked, which tells the valve body it's time to shift to a lower gear. Normally the solenoid keeps the opening blocked.
Open = kickdown, closed = normal driving.
 

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7 in. of vacuum is where I've had issues with a T400 shifting late. I got an adjustable mod valve from TCI, cured my issues. Just my .02
 

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Discussion Starter #10
...The valve in the center opens and fluid is dumped from the passage that is normally blocked, which tells the valve body it's time to shift to a lower gear. Normally the solenoid keeps the opening blocked.
Open = kickdown, closed = normal driving.
Thanks John. I will look at this unit more closely when/if I drop the pan.

Sounds like not enough vacuum 7# not much
Do you have the pin in the modulator ?
What pin are you referring to? The adjusting screw is in and back off all the way (not removed). I removed it once just seeing how far it would back out and simply screwed it back in.

7 in. of vacuum is where I've had issues with a T400 shifting late. I got an adjustable mod valve from TCI, cured my issues. Just my .02
Mine's just a generic adjustable replacement unit. However I just read today that there are "low vacuum" adjustable modulators which I will check into. Thanks for the input.
 
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