truck transmission diagnostics

GM 6L80E/6L90E Transmission information

General Motors introduced the 6L80E transmission In 2006 for the Corvette and then it was put into Chevrolet and GMC truck chassis in 2007, 8600 GVW and greater, Hummers and Cadillac XLR-V and STS-V

The Hydramatic 6L80E transmission is a computer controlled 6 speed automatic transmission with torque converter clutch, and can be found behind  a V8 engine, 2 wheel and 4 wheel drive versions.

Technical information for 6L80E transmission

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Complaint: Transmission slips in forward range, first gear take off. P2723 P2728
Cause: Possible codes P2723 Sol 5 stuck off or P2728 Sol 5 performance, Very possible that the number one check ball in the valve body has shrunken and wont seal or is missing. This ball can be replaced with the 1/4 inch Chrysler check ball from a 47RE or 48RE etc part #

52118261 this ball is much more durable and wont shrink or disappear.

Complaint: Neutrals or flares on the 1-2 shift.
Cause: The low Sprague may be failing,(will only happen in drive range, if you try manual low you will not have up shift problem when manually shifting).There's is an updated Sprague element that came into production in 2008 with 38 elements and if you have the 30 element Sprague always update it.
Converter clutch shudder, slipping gears, overheating.
Cause: The Pressure regulator valve in the pump is worn out in the bore, as well as other valves in pump and valve body. sometimes this causes complete burn up of the unit also. with over 100,000 miles this is a high wear area in these units and almost always needs to be repaired as well as other valve bores.
Complaint: Truck wont move in reverse, seems bound up, forward ranges ok.
Cause: Likely problem here is the end of the park rod is breaking and its holding the truck in park still. shut off engine in reverse and see if truck will roll, if wont then this is your problem. if does then you have damaged clutches etc. remove the linkage and park rod and look at the end, it may be the crimp is worn/broken off and end of rod has slipped off the end. GM part number for park rod: 24242085
Complaint: Slips in reverse, 2-3 flare or slip, possible ratio codes.
Very common problem that will cause a reverse slipping complaint and slipping 2-3 or flare in other shifts, Ratio codes etc is the 1-2-3-3/5-R drum has developed a crack around the bottom of drum under the piston, when removed you can visually see the crack if you look from the outside where the thrust bearing sits on bottom of the drum. QWE replace these on every overhaul that has any mileage on it, especially over 100K. There's 3 different drums depending on the unit so be careful and get the correct one.
gm 6l80ee transmission gmc 4l60e transmission