Alright guys I am going to try and explain this without being to confusing. I have a 1996 2500 with the 6.5L/4L80E combo that one of my guys has just taken over at another maintenance shop and it won't shift higher than 2nd gear.

A brief history like I said we just took this project over and the transmission was just replaced in it before we showed up (it has 5 miles on it). No codes are being thrown and fluids are good to go. All advise is greatly appreciated.

Seabee we need to know what you have. Being military I would like to ask you if the truck is the military hummv. If it is then take a look at the transmission control module located behind the driver's seat and under the passenger's seat. You will see the smaller of the two connectors. Take the cap off and look for the pins A and E. They are referenced like the ten and the two o clock position on the hour dial. This is how you can retrieve codes. Take a wire and short these to together. Turn on master power and make sure you have full contact at Pins A and Pins E.
code 12 will show up first. Like this Flash- Flash-flash at the check transmisison light next to the shifter. If there is something else coming up as a code then there will be more to follow.

Code 22 is TPS circuit low
Code 21 is TPS circuit high

Look for possible codes 85,86,87
Undefined ratio, Low ratio and high ratio respectively.
GB

The transmission is in a 1996 2500 Pick-up. The guy that is working on it has checked voltage, fuses, grounds, wiring, and everything checks out. As I stated earlier the transmission was replaced just prior to our arrival and has about 10 miles on it. We have tried everything and I have lead him over the phone during trouble shooting and we are still making no progress. The last words we recieved from a chevy dealer back in the states was that it is the ECM. Any other suggestions.

Yep: Vehicle speed sensor. Take a look and see if the connections are good. If not then replace it.

Check for voltage going to the transmission.
Check for good grounding its redundant, I know.
See if you can retreive codes. Disconnect the transmission pass through connector and see if there is voltage at Pin E. See the stickies posted. Pin E provides voltage to the shifting solenoids and the TCC solenoid.
Check and see if you have voltage at the ECM.
If you don't then find the fuse or relay going to the ECM.
No voltage = 2nd gear.
If you retreive codes then you have a ballpark figure to go on.

GB

ok does it get 1st gear? if it dosnt and just has 2nd gear then it may be in limp mode. if its in limp mode it may have a inernal failure. Second gear is a direct drive which is why it can limp into it when there is a internal failure. I just had this happen to my truck 2 weeks ago and tommorow I will be finally wraped up with the rebuild. Two of the teflon seals wore out and couldnt hold pressure any longer so the truck went into limp and only had second. ok thats my two cents.

Justin

It will get 1st and 2nd gear.

Any codes?

Any scan data?

Was the trans rebuilt? if it was by whom?

If it will get into first and into second gear then your transmission is getting the electricity it needs. Drop the pan and look for the 2-3 shifting solenoid. There is a difference between the 1-2 which is the first gear and the 2-3 which is the third gear.
Take a none volt battery and solder two leads to it. and see if the solenoid clicks. You can do it with the pan dropped. If it is clicking then take a star socket and remove the solenoid and inspect the screen for blockage. If not then check for resistance. It should compare to the 1-2 shifting solenoid. if you get an OL or higher resistance then replace.
The computer feeds the 1-2 and the 2-3 shifting solenoids with the same pin. Check the connectivity through the pass through connector located at the connection going into the transmission. Pin B and E for the resistance check.
The ECM might be to blame at the ground wire for connectivity.
Probable causes to your headache.
Screen clogged.
Solenoid fell into the pan.
Stuck 2-3 shifting valve, this one is a long shot.

You will see this one to fruition.

GenBiltstein

No codes and no scan data. The transmission was purchased at a Chevy dealer in the states and sent to the trucks location overseas.

Does the ECM need to be re-flashed for the new transmission and if so what is the process or should I ask is a TECH-2 the only way to do it.