TH400 won't shift?

89wrangler

89wrangler

Not a new member
Joined
Oct 22, 2005
Location
Bostic,NC
On a 77 Chief. Had to replace a rusted tranny line that decided to start leaking. Actually was starting to back it of the shop when it happened, so I shut if off, cleaned up the mess and got a new line for it. Since I was going to have to add fluid I went ahead and pulled the pan off and changed the filter. Installed new line, and filled with fluid, went to drive it this morning and will not shift out of first geat?? shifted great prior to changing the filter. Anyone have any ideas or suggestions. Thanks
 
Modulator line is good. Fluid is full.

Now about this O ring. I do not recall seeing/having that??
 
I just pulled the filter off the plastic tube. I assume now that there is an O ring at the top of the tube. Hmmm I wonder if I pulled it down when removing the filter and it is not seated all the way?? I will check the vacum line up the engine when I get home. If it is all good, I will remove the pan and filter and check the tube to make sure it is seated properly.
 
OK, got vacum to the modulator. Low and behold there was a O ring in the filter box( should have looked as I just grabbed the filter and gasket :shaking:) I removed the pan again and pulled the filter tube and installed the new O ring and made sure the tube was seated well and reinstalled filter and pan. Refilled with tranny fuid and same damn thing. It does appear it is shifting from 1 to 2nd as if I pull it down to 1st, when I slow down it will finally shift to low. Is there a way to test the modulator?
 
Removed the modulator just to check it. Was good. Removed the govenor just to look at the gear and it was good. Went to unplug the wire on the driver side and it was aready unplugged?? So I plugged it in. No difference!
Let me ask this question, after looking at every possible thing I could think of, the only thing I did was change the line and the filter. I did notice that there is a tight bend in in the new line. Is it possible that it could be "starving" for fluid? I am at wits end on this thing.
 
Changed the line again that broke this evening again to make sure there were no restrictions. No difference, Still will not shift into drive. Now if I take the tranny to someone, what is the next step?? I can't belive that minute it works fine and the next it does not without any symptoms. POS!
 
Wash the old filter in kerosene or varsol, if you still have it, and put it back in the transmission. The new filter may be the wrong one or defective and new "O" ring may be wrong size and cavitating the pump. Are you positive you have the minimum amount of fluid in the pan?

Just some ideas.
 
there is only one filter for the 400, it fits 67-98, the only differences are felt or brass.
when you put the filter on, was there a spacer between the filter and valve body? (it is supposed to hand kind of loose)

why were you dropping the pan?
was there anything in the pan?
 
transman731 said:
there is only one filter for the 400, it fits 67-98, the only differences are felt or brass.
when you put the filter on, was there a spacer between the filter and valve body? (it is supposed to hand kind of loose)
why were you dropping the pan?
was there anything in the pan?
Click to expand...
The only reason I dropped the pan was to change the filter since I was replacing the broke line. Being I did not kow the history and have never changed it since I bought it a few years back, I "thought" it would be a great idea..:lol: And yes, there is a bolt on the center of the filter with a shoulder on it to let the filter hang somewhat loose.
Caver Dave said:
How'd you check this?
I've had the no up-shift issue twice... 1st was the vac line NOT attached, shortly after initial "assembly" & 2nd was the vac line (stc. rubber tube) getting a hole burned in it against the exhaust manifold
Click to expand...
I used the tried and true method of holding my finger over the line. It has a metal line from the intake down the modulator and 3" rubber hose at theat point.
I am going to remove the line today and inspect it closely to rule out that part of the equation.
Thanks for eveyones input thus far, I appreciate it!
 
Removed vacum line today, no leaks and great vacum. figuring I had done all I could do, I thought WTF, just buy a new modulator and see what happens. Spent $12, took the 20 minutes to put it on, crossed my finger, finished my beer and took it for a test drive THE DAMN THING SHIFTS GREAT!! :driver::beer: . not sure what is wrong with the old one as it does not leak and it pulls in when vacum is applied, but life is good again in waggy world :lol: Also since hooking up the wire on the driver side, the kickdown actually works again.
Thanks for all the input guys! :beer:
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