4L60E (or 4L80 not sure which) in my buddy's truck made a metallic clunk as he was accellerating, after that still had forward gears but NO reverse. Still shifts but goes to around 4000 RPM's before shifting. Truck is a 97 chev, 95000 miles, never used for towing. I checked the fluid and it is still clear and does not smell burnt. I checked the shift linkage (cable) and it is working properly, shift linkage hits all the detents so it is still in adjustment. I'm not real familiar with these transmissions so I don't know what may be wrong. Anyone out there have a clue?
sounds like its time to drop the pan and do an inspection?
I don't know what I'd be looking for.
The trans in a '97 truck is a 4L60e unless the truck is 3/4 ton or larger.This will help identify the transmission.http://www.crankshaftcoalition.com/wiki/General_Motors_transmissionsFrom the ATSG Technical Service Manual:No Reverse or Slips in Reverse1) Input housing assembly a) 3-4 apply ring stuck in applied position b) forward clutch not releasing c) turbine shaft seals missing, cut, or damaged2) Manual Valve link a) disconnected3) Oil pump assembly a) retainer and ball assembly missing or damaged b) stator shaft seal rings or grooves damaged c) stator shaft sleeve scored or damaged d) reverse boost valve stuck, damaged, or misassembled e) cup plug missing f) restricted oil passage g) faces not flat h) converter clutch valve stuck4) Valve body assembly a) 2-3 shift valve stuck b) manual link not adjusted c) spacer plate and gasket incorrect, mispositioned, or damaged d) lo overrun valve stuck e) orificed cup plug restricted, missing, or damaged5) Reverse input clutch assembly a) clutch plate worn b) reverse input housing and drum assembly cracked at weld c) clutch plate retaining ring out of groove d) return spring assembly retaining ring out of groove e) seals cut or damaged f) restricted apply passage g) porosity in piston h) Belleville plate installed incorrectly i) excessive clutch plate travel j) oversized housing6) Lo and reverse clutch a) clutch plates worn b) porosity in piston c) seals damaged d) return spring assembly retaining ring mispositioned e) restricted apply passage