Upgrading/modifying 4l80e For Towing?

dragr1 · April 7, 2008

I'm not real pleased with the towing ability of the transmission in my '00 Suburban 2500 6.0 4x4. Sometimes it seems to "ride" the torque converter for extended periods while towing. It doesn't do this all the time and it doesn't do it when climbing big hills. It seems to mostly do it on very gradual grades or on rolling terrain. For instance, when it does this, it will run 3000rpm at 60 or the same rpm at 70mph. It should run 3000rpm in 3rd at 70mph properly.

It doesn't do this all the time, only sometimes. On my recent 900 mile towing trip I crossed the Cumberland Gap at the Tennessee/Kentucky line twice and had no trouble and ran 165 degrees trans temp. at the base and up to 195 degrees at the crest-but it came back down to 165 after the crest, but when on a very very gradual grade is when it heated up to 200 degrees and stuck there. If I pulled over and turned off the vehicle for a few minutes and then continued on, it went back to running at 165 degrees. When it does this "ride" the torque converter scenario-once the temps get up to around 200, then the transmission shifts really hard-abnormally hard and this is the only time it does that.

The vehicle has 109k miles and the torque converter was replaced about 2 years ago-which is 1.5 years before I bought it. I believe the trans. was also rebuilt at that time.

Ideas on the problem? How to fix it right for no issues while towing? Valve body or torque converter upgrade?

markw8 · April 9, 2008

What is ride the torque converter? Mark.

dragr1 · April 10, 2008

What is ride the torque converter? Mark.

I couldn't come up with a good way to explain-it's my own terminology for torque converter slippage. You know how the torque converter slips to allow you to accelerate, well sometimes mine gets hung and continues to slip and heats up the transmission to 200 degrees in doing so.

markw8 · April 10, 2008

Looking back at your earlier posts, Your 285 tires are killing you for towing if you indeed have 3.73 gears. Your burb is probably a good bit over 6000 lbs with people and gear, when you pull your trailer. Also if you haven't actually weighed your trailer, ready for a trip, its almost certain it weighs more than you think. Mark.

dragr1 · April 10, 2008

Looking back at your earlier posts, Your 285 tires are killing you for towing if you indeed have 3.73 gears. Your burb is probably a good bit over 6000 lbs with people and gear, when you pull your trailer. Also if you haven't actually weighed your trailer, ready for a trip, its almost certain it weighs more than you think. Mark.

285's have been gone, I have 245's now. Trailer and truck on the trailer weigh right at 6500 pounds combined-1900 for the trailer and 4600 for the '85 4Runner on the trailer. 2 people in the Burb and some tools, but not a lot. So, I'm still under the tow, GVWR, and GCWR rating.

Also have a much larger transmission cooler (stacked plate), new transmission filter, and fresh synthetic fluid. Transmission runs around 165 degrees towing unless it goes into the slippage mode that I'm describing.

markw8 · April 10, 2008

I thought it was a travel trailer. You should have it checked by a good Transmission Tech. Before you hurt it. There might be some problem, thats not allowing the converter to stay locked up in third gear. It should always unlock in second. I have the 6.0 4-80 in my 2000 sileverado. I'm about 9800lbs with my camper. 245 tires with a 4.10 diff. 60,000 miles. So far trouble free. Mark.