how do I diagnose solenoid block?

[charbojoseph]

I have an '02 XLT with the 4.0 and 122,000 miles that has been giving me a code P0775 on and off for a couple of years now. It used to be every couple of months. Lately it is every other day. I have searched and read that it could be one of any of these or a combination of them

1) bad solenoid
2) servo bore worn
3) valve body
4) need to have PCM flashed

When the OD light starts flashing I have no noticeable driveability symptoms. No shift flares, no harsh shifting, seems to shift fine through all gears and into overdrive. I am leaning towards replacing the solenoid block and replacing the fluid and filter since there are no symtoms other then getting code P0775. I'll also check and adjust the bands while I'm in there. Is there a way to diagnose if the solenoid is bad? Am I heading in the right direction? What transmission do I have? From what I have been reading I either have the 5R55W or the 5R55S. How can I tell which une I have. This was one of the first 3rd generations out of the shoot. Built in May 2001. Thanks for any help and advice you can give me.

 

[BrooklynBay]

The 2002 has a 5R55W. Do you have the original solenoid block?

 

[charbojoseph]

I haven't changed it yet. Based on the symptoms I have (or lack of) I was just wondering if the solenoid block is the most likely culprit? If so is there any way to diagnose it before I spend the money on a new block?

 

[BrooklynBay]

The proper way to test it is with a special transmission scanner capable of cycling the block while it monitors the output. The test signal simulates a certain driving condition, then the solenoids have to respond accordingly.