trannie going south, please help with diagnosis

[dwalin]

i have several problems with my 4r55e and i need help with diagnosis.
first problem: flashing o/d off. in my case it starts flashing always on downshifts 4-3. i think that's overdrive servo leaking or something. am i correct?
second problem: harsh 1-2 and 2-1 shifts, especially on a cold trannie. when i start driving, first time (several shifts) there's a muffled "thump" on 1-2 and it's like something momentarily holding the truck back, it loses momentum but after shift it goes okay. on 2-1 downshift there's a loud "boomp" somewhere under the truck, with a sensible punch in my bottom. i think that's a servo again, this time intermediate one. what else could it be?
and the most annoying problem: loud humming on the first gear. when i start from complete stop, humming begins and raises with engine rpms, gets louder and louder and then "thump" -- gear switches to second and humming stops. it doesn't hum on second and higher gears. i think that's front planetary sends me love letters.
2-3, 3-4 and 4-3, 3-2 shifts are okay more or less.
please share your ideas, i'm considering doing rebuild myself. or is it better to find a reputable rebuilder?

 

[BrooklynBay]

Those harsh shifts sound like your transmission going into FMEM (limp) mode. Have your vehicle's codes pulled to see what is causing the flashing OD light. This is the equivalent of a check transmission light.

 

[dwalin]

BrooklynBay,

thanks for an answer. i'm sorry i didn't make myself clear in the first place: o/d off light doesn't flash most of the time just because i'm driving with o/d switched off. i very rarely drive at highway speeds for a long time, mostly it's town and traffic jams kind of driving, so i turn off overdrive before departing to save overdrive pack. and harsh shifts are occuring with overdrive turned off.
i tried to scan codes but got nothing, just nothing. once i drove to the local ford shop with o/d off flashing and didn't turn off engine so they could "catch" it while it's hot. no way, to scan codes i had to turn off the engine and when i started it, there were no codes. except o2 sensor but that's another story...
today i tried to "warm up" the tranny before driving, i started the engine and put selector into "drive" and held it for two or three minutes, then did the same in "reverse" position. i noticed that after this "warming up" thumps and bumps were quieter...

 

[BrooklynBay]

Some code readers won't read vehicle specific proprietary codes. What type of code reader are you using? The better quality scanners read proprietary codes.

 

[dwalin]

BrooklynBay,

truth to say i don't know what kind of scanner was used. i never thought there are several types. can you tell me what kind of scanner should i look for?

 

[BrooklynBay]

The more expensive scanners could read most codes. The cheap code readers can't read everything. You need a scanner that could read Ford proprietary codes on an OBD-II (EEC-V) vehicle. Some auto parts stores could read codes for free such as AutoZone. I don't know if they have them where you live. The dealer, and transmission repair shops would be able to read your codes, but charge. WWW.Atra.Com has a list of transmission shops, but I don't know if they have them listed outside of the USA.

 

[dwalin]

BrooklynBay,

thanks, i'll try to find a dealer who has such a scanner.
but flashing o/d off is not the most serious problem, i don't use overdrive and that's all to it. can you say anything about other two problems? i'm afraid that this humming is not okay. low/rev planetary? *sigh*