Last week the transmission in my super coupe began acting up. It shifts into 1 and 2 just fine but wont go to 3 or 4. I have no clue what may be wrong. I have found a 4R70W from a 98 mustang gt. Would this be a direct bolt on replacement? Or would it not work? Should I try to fix the transmission I already have in there? Thanks for any and all advise.
Perhaps you have a bad accumulator piston, a valve body issue, or a sensor issue.
If the fluid is fine (not low & not burnt), I would drop the pan and valve body, and take a look. If you drop the pan and find a lot of metal, you may have serious clutch problems, but some fine metal sludge is normal.
About 10 years ago, my '94 LX stopped shifting from first to second. Knowing it would cost a small fortune to replace the trans, I dropped the pan & valve body to have a look. I'm an amateur, but "fearless" sometimes when messing with cars.
When I dropped the valve body, I could see the 1-2 accumulator piston was jammed almost sideways in its cylinder. It was a very easy fix.
While I had it open, I replaced all the accumulators/pistons, sensors, and rebuilt the valve body with a TransGo shift kit. TransGo included a video, and even a dumbazz like me could follow the instructions.
*** Important note: The Overdrive piston/servo has to engage with the O/D band.
This video shows you how to install the O/D servo, but you DON'T have to pull the trans from the car. This guy uses a special tool. I didn't use any special tools. I think I used a coat hanger.