4R70W Issue Found - Just For Future Reference

[Rootsy]

I'd posted asking about a transmission issue recently. Transmission would go into what appeared to be gear but would not move.. or began to move slowly as rpm was increased... Or it would not move at all and then it'd engage and go forward quite abruptly... chirping tires and jarring the driveline... severity was worse some days than others... finally it would be ok from a stop sign but when first starting the truck and engaging in gear it would not go... well finally it about stranded me... was working "better" when finally 35 miles from home i fired her up and she wouldn't move... had my buddy push the truck and it came in slowly and we were off... and made it home somehow A few pointed to the forward clutch being the failure... (i had wishful hoping that it was something less involved) upon disassembly i found that indeed the forward clutch assy looked pretty dismal.. the drum was stained black inside, copious amounts of friction material... and small pieces of rubber... the root cause of the failure i believe is the outer seal on the forward clutch piston which had deteriorated allowing fluid to flow by instead of engage the clutch with full force... about a 1/4 of the way around the lip is missing. Aside from the Reverse sun shell slots being slightly worn and the mating drum fingers everything else inside looks peachy... cept dirty... no ring wear, no stuck rings, no broken or damaged parts or damaged seals, all of the bearings are good... gonna do a standard master rebuild kit and bearing set... check everything that needs to be and put her back together... i have a feeling that this failure was a long time coming and i just never really "noticed" it until it reared it's ugly head... for a long time the truck has felt very rubber bandish from a standing start, especially with a load on the hitch... any other ideas in case i've forgotten something? guess i can't complain too much... first "major" issue in 193,000 miles other than grenading an A/C compressor clutch assy... Thanks for the help Jamie

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[Drdexron]

Make sure you replace the Electronic Pressure Control solenoid while you are in there. They are bad about sticking because of contamination after an internal failure. I would also replace the 1-2 and the 2-3 accumulator pistons, OD band, and the torque convertor.