Hi there. I have a 2007 Hummer. I have a bit of a problem with the gearbox. It shifts perfectly fine 1st and 2nd but as soon as it goes into 3rd it just refs up, like there is nothing. It is exactly the same if i manually change the gears. So i dropped the pan and took off the valve body. What i did find is that the 3-2 control valve spring was broken and that control valve was loose. Now whould that broken spring cause the 3rd gear to slip like that, or is it rebuild time for that gearbox.
Any help would be greatly appreciate

Thanks Andre