I have a 2002 2500hd with a 6.0 4l80e. It had 260k trouble free miles on the clock, but I felt that it was a time to tear it down for a rebuild. The trans was making some noise, and I tow a car hauler with vehicles on it all over the country. The whole point was to make it reliable. I did some modifications to raise line pressure and to shore up the hydraulics of the trans. I am tuning it using HP tuners.

This years vacation is taking us from Missouri to Colorado with a 1971 k5 blazer on the trailer. The trip hasn't been great so far. It kept getting hot and puking out fluid.

I got everything running and was excited at how well it was running. I drove it daily for a couple months with no issues. The first 100 mile interstate trip at 75 mph unloaded showed a problem. The trans was getting hot. I have HP tuners software and the using the scan tool I could see that the converter was slipping causing heat. I found a table to offset the pressure in the TCC circuit and raised the pressure. That worked great. We drove a 600 mile trip unloaded at 65-85 mph with no issues and single digit slip rpm in the TCC and sub 200 degree trans temp.

Then when we took off for vacation with a loaded trailer more problems arose. The TCC was slipping again. No change in programming that I can find will fix it.

The very wierd thing is, I believe it may be tune related because it will throw a code p0741 or p1870, once I clear the code (I can clear it running down the road), it instantly locks up perfect. It will lock up fine for a little while, and then acts up again. When it is locking up good, the trans will run less that 200*. When it acts up, it goes to 240+ and pukes out around 2 quarts of fluid before I can find a spot to pull over.

I have played around with the other trans related parameters in the software, but cannot seem to make any headway.

I find it hard to believe that it is a mechanical problem because it locks up so well after I clear the code.

One other thing that seems different is that it seems to be getting hot in situations where it didn't. Last year before the rebuild, we took a trip to Gulf shores AL. Towing through the hills of MS, it would barely stay in OD. Instead of letting it shift in and out I just left the shifter in D3 and let the motor sing at 3300 rpm for 10 hours. It never got over 210 doing that. I tried that yesterday going through KS, and it got hot super quick.

I apologize for the long post, I am just trying to lay all the info out that I can.

If anyone has any suggestions please let me know. We are still on vacation in CO, and I need to get this thing back to MO. I am thinking of buying a new deeper pan to increase capacity by 3 quarts because I am grasping at straws.

Thanks
Lynn

 

Not a trans expert by any stretch. It seems that increasing TCC lockup helped you for a bit. So 2 thoughts.........torque converter disc is slipping or o-ring on end of input shaft into torque converter is leaking causing inconsistent lock up. 3rd long shot maybe bad ISS or VSS sensor causing a mismatch of reported speeds and causing converter to unlock?