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Old 06-19-2018, 08:35 AM   #7
YoungPup1977
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Join Date: Jun 2015
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Re: th400 won't 2-3 upshift at WOT

Quote:
Originally Posted by americanmusc1e View Post
I recently rebuilt my th400 and then i went through it all again after the torque converter had a bad sprag and left metal in my pan.

Stock th400 rebuild with 32-element sprag and Fairbanks shift kit. Shifts normally at part throttle though it is quite a bit softer than the fairbanks equiped 46re I rebuilt for my jeep.

I finally got the kickdown wired in and about 80% of the time if I floor it on the highway it will kick down to second and hold second until greater than 6500rpm (the remaining 20% of the time it upshifts at 4000 with the kickdown on). When I let off it shifts. The 1-2 shift happens at 3600 with the kickdown.

today I pulled the governor and replaced the worn gear, made sure nothing was sticking and re-calibrated it with slightly ligher weights and springs. I took it out on the highway and for the first couple tries it shifted 1-2 at 3600 and 2-3 at 5500 with the kickdown engaged. Then after I was feeling pretty good it went back to not upshifting out of second at WOT. What should I check next?
You indicated you recently rebuilt this TH400 that you are having issues with....

With the sprag letting go in the converter, lots of metal in the pan....

How was the 2-3 shift valve during your rebuild ? You sand the valve for easy operation of the valve since lots of metal was in the trans before rebuild.

Did you replace the kickdown/detent switch during the rebuild ?

You indicated you replaced the gov gear after rebuild along with installing different weights, why do you think the gov is still bad ?

Did you clean out the cooler lines real well before hooking the lines to the rebuilt trans since lots of metal was ran thru this th400... How did you clean out the lines and what did you use to do this ?
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