My vehicle has 195K miles on it today. As far as I can tell the tranny has never been replaced.

About twice a year I will tow a small 6x12. Weight around 5.5k lbs. If you know I40 in TN (good sized rolling hills but not mountain passes) then you will understand the conditions. Usually I will tow in 4th gear + tow/haul mode. In the past I have heard it isn't a great idea but I never had any trouble. Sometimes I would manually downshift but generally it went great and had plenty of power.

Yesterday I drove out of OK tying to escape the ice storms. hah. When I got to TN I was towing in D and noticed what felt like 40% less engine power. Terrible. But it didn't feel like "slipping." My tranny temps kept climbing despite the rain and got up to 230. It caught me off guard. I shifted into 3rd and the power came back. 3200 RPM. Felt great. Tranny temps went down to 140 within a minute and then sunk so low the gauge almost didn't register.

When I got home I noticed the smell of burnt fluid. The vehicle seems to drive OK in D w/o the trailer. I am trying to get the max miles out of this tranny. So if D starts slipping how long can I keep the wheels turning if I just always use 3rd gear?

Since I live in the DC area I really only use this vehicle if I got out to "Real Virginia," when it snows, or for Home Depot runs. I have money saved up for a 4L80E swap. Also considering NVG4500. But I'd rather do it during the spring in case it snows this winter.

 

Change the fluid,if it got that hot it is cooked. And keep running it. Watch the rpm when locked up in 4th and you will be able to see if the clutches are toast.

 

Good chance it's toast.

Do a fluid flush/change and report back.

Do you have a tranny cooler?

 

Even with my cooler I hit 95c often towing I just do changes after it gets over 100c even if you have to replace the 3-4 clutches it's pretty cheap

 

I am VERY familiar with that section of road and also towing with anything 700r4 based. It honestly sounds like you may have cooked the torque converter clutch. Once the converter is unlocked you are causing a tremendous amount of heat in your transmission.

I was on this same section of interstate just last Saturday and Sunday. I made a round trip to Ohio and back in 52 hours. I-30 out of Dallas/Fort Worth to Little Rock, I-40 through Memphis and into Nashville, then turned north on I-65 and drove through Bowling Green. In louisville I turned up I-71 and drove up to Cincinatti.

I was not towing, but I was pushing my 6,200# Express van hard and on the return trip had about #500 of parts in it. We were over 7,000 lbs on the return trip. With the 4L80E and converter locked, even before the rain started coming down, I was seeing trans temps in the 120-130*F range.

 

I NEVER see anything over about 180-190*F even WOT on the floor in 2nd gear on a 105*F day. Even with the 4L60E it never got hotter than that. Factory cooler in the radiator plumbed in before a large external cooler.

 

Do you run a stall converter?

 

I had a S10 converter that stalled about 2,600 rpm in the 4L60E and have a 10.5" Pheonix Trans converter with a 2,600 stall speed rating (brake stalls 2,750) in the 80E. My Tow/Haul schedule is pretty aggressive about keeping it locked under load above 40-45 mph though.

 

Once the tranny gets super hot the teflons and seals like to harden and stop sealing very well unfortunately, 'twas a little over a year ago when I was 16 I did some very 16 year old with an LS truck things and toasted my first 4l60e

I love my 80e, I think you'd do well with the swap especially for where you drive and towing, pretty straight forward, good luck!

 

^^Agreed! After going through about 8 of the 700r4s and 4L6xs in my life, I finally swapped to a 4L80E and it has been good.