M1009 Takes off in 2nd gear

[Shankem-Deep]

I just put a rebuilt th400 transmission in my 09. It has a new vacuum modulator, new vacuum valve set correctly, and new vacuum lines. It shifts through the gears fine until it gets warm. After it's warm, it stays in 2nd gear when taking off from a stop. I can manually down shift it to 1st and it takes off in 1st. I can also down shift to 1st while stopped and then go back to D and it takes off in 1st and shifts normally until I stop again. I've searched but can't find a similar issue. I only have around 10 miles so far on the transmission. What do you guys think I should check?

 

[Skinny]

Could be a governor sticking like it's spinning up. May be a stuck 1-2 shift valve in the valve body. I would highly recommend running through a trouble shooting chart. One, triple check the fluid level. I would invest in a set of pressure gauges to see what your governor and throttle pressures are at to verify the governor is functioning correctly.

 

[Shankem-Deep]

Fluid level is correct. I re-used the governor from my old transmission. I'm going to start with the governor since that is easy.

 

[cliffyp]

I looked through the trouble shooting section of my TH400 service manual. There is nothing in there about starting in second. I would agree with Skinny, stuck valve or governor. Let me know if you need the pressure specs, I'll get them out of my service manual.

 

[Shankem-Deep]

I drove it to lunch today and it shifted perfect. I may not have got it up to full operating temp though. Only about 10 minutes each way.

 

[Shankem-Deep]

Well I've been driving it for a few days and it only takes off in 2nd from a complete stop every now and then. So whatever is causing it is random. I can't duplicate the problem, it just does it sometimes. I still may take my governor out and clean it up really good. When it happened last night I floored it and it down shifted back to 1st and took off great.

 

[Shankem-Deep]

I took the governor out and it was stuck. I drove out the pin that holds the gear on and took out the rod that is supposed to move up and down. I used brake cleaner and cleaned everything really really well. I then chucked up the rod in a cordless drill (lightly) I used 320 grit sand paper to smooth up the rod. I folded the piece of sand paper in half and used the folded edge to put a chamfer on each groove. They were machined with sharp edges. I then used scotch brite to smooth up the rod even more. Finally I buffed the rod, cleaned it again and put the governor back together. Put it back in the transmission and i've been driving it for a few days without a single 2nd gear start! I think this fixed the problem!

 

[Skinny]

You owe me a beer! Although it sounds like you had way to much fun cleaning the rod...pun intended.

Glad you got the ol' TH400 squared away. Have to live the old iron...so simple to fix.