OrdnanceMarine
New member
I just finished my first camping trip towing my '06 Jayco 1206 camping trailer and had just received my ScanGaugeII back from the firmware upgrade that allows transmission temp to be displayed and wanted to post some observations. I also did some steep extended trail driving up to what was one of the largest silver mines in the United States, Cerro Gordo (second only to Virginia City - Comstock).
My trailer is rather large for a pop-up and was probably in the 3200-3300 lb range on game day so between that and what we had in the tow vehicle itself I'd estimate we were rolling with 4000 lbs of payload. We towed from 2300' and 100 degrees outside to 3700' and 95 degrees and with a few light to moderate grades along the way with the air conditioning on all but a few times when I wanted to see if eliminating that parasitic drag would help (Highway 395 from Ridgecrest to Lone Pine).
Right away I picked up that if the transmission was in 4th or 5th and the torque converter was locked up then the trans temp would be around 175 plus or minus about 5 degrees. When the torque converter unlocked the transmission temp would immediately begin to climb. The longer the grade, the more the climb, getting up to around 200 before I'd either finish the climb or if it was in 5th gear, before I'd bump it to 4th and once the torque converter locked up, the temp would quickly drop back to ~175. This was very predictable and allowed me to bump the transmission in to 4th just ahead of an incline so I could both maximize fuel economy while preventing a mid-hill shift from 5-unlocked to 4-unlocked and helped keep the temp down.
Then I turned off of HWY 395 and climbed up a fairly steep grade between 25-35 MPH, going from 3700'-4800' in 2.5 miles. Here transmission temps quickly rose into the 220s during the first mile and over the next mile went up to 240 so I pulled over and let it rest in neutral for 2-3 minutes and the temp dropped to 220 and I finished the climb, peaking again at 240. At no time did the engine have any trouble pulling the load; instead I was concerned about cooking my transmission.
We made a turn and I accelerated on a slight downhill until I could get 4th gear to lock up and as soon as that took place the temps dropped below 200 fairly quickly. Another 2 miles and we turned up the trail to our campsite and climbed 400' in about a mile at about 10-15 MPH and temps gradually climbed but didn't exceed 225.
I let it run for another 5 minutes while I backed the trailer in to the site and got situated. While there was plenty of heat pouring off the car nothing smelled hot. Bottom line here is that if you're not in 4th or 5th gear with the torque converter locked up then the transmission temp is going to climb above "normal". If the torque converter is locked up (only in 4th and 5th gears, right?) you can tow as fast and as long as you want with no rise in temp. How high the temp gets with the torque converter unlocked depends on how steep the grade is and how long you're running it (I'm sure ambient temps has an effect as well).
The next day my folks came along in their 4Runner (2008 V6 4x4 Limited) to Cerro Gordo. Here you climb from 3600' at Keeler, CA (old shore of Owens Lake) to 8200' in pretty short order. The first mile or two is a gentle climb out of the valley and then it turns in to a consistent steep grade for maybe an additional 5 miles. The trail is in good condition and has the typical broken rock, sand and dust that accompany many of the trails in the Mojave Desert and surrounding mountains. I drove the first section with the transfer case in 2H then switched to 4H about 1/3 of the way up. Transmission temps were in the 220-230 range through here (not towing anything). Then I went ahead and shifted to 4L and transmission temps stabilized but the grade increased some. Out of curiousity I switched back to 4H and was in 2nd gear and temps quickly climbed to 242 and showed no sign of stopping so I shifted back to 4L and the temp stabilized at 235-237 the remainder of the climb. Bottom line here was even though 4H was getting the job done, 4L was giving me a slightly cooler transmission temp.
I have plans to haul this trailer all over the Sierra Nevada and surrounding mountains with many destinations taking me through extended steep and slow grades back canyons, trails etc. so I am pretty much convinced I need to find a good way to keep my transmission from burning up.
Does anyone have good suggestions for a transmission cooling mod for this situation? Right now I think that an aux cooler in front of the radiator alone may not be enough. Will I need to add a cooling fan to it to get the performance I want, especially for slower speeds when airflow won't help to cool things as much?
Any suggestions?
By the way, I was very happy with the fuel economy while towing. I kept it at 55 MPH on the highways and averaged something like 17.6 MPG on the way up and 20.2 MPG on the way back. I had anticipated 15 MPG overall.
My trailer is rather large for a pop-up and was probably in the 3200-3300 lb range on game day so between that and what we had in the tow vehicle itself I'd estimate we were rolling with 4000 lbs of payload. We towed from 2300' and 100 degrees outside to 3700' and 95 degrees and with a few light to moderate grades along the way with the air conditioning on all but a few times when I wanted to see if eliminating that parasitic drag would help (Highway 395 from Ridgecrest to Lone Pine).
Right away I picked up that if the transmission was in 4th or 5th and the torque converter was locked up then the trans temp would be around 175 plus or minus about 5 degrees. When the torque converter unlocked the transmission temp would immediately begin to climb. The longer the grade, the more the climb, getting up to around 200 before I'd either finish the climb or if it was in 5th gear, before I'd bump it to 4th and once the torque converter locked up, the temp would quickly drop back to ~175. This was very predictable and allowed me to bump the transmission in to 4th just ahead of an incline so I could both maximize fuel economy while preventing a mid-hill shift from 5-unlocked to 4-unlocked and helped keep the temp down.
Then I turned off of HWY 395 and climbed up a fairly steep grade between 25-35 MPH, going from 3700'-4800' in 2.5 miles. Here transmission temps quickly rose into the 220s during the first mile and over the next mile went up to 240 so I pulled over and let it rest in neutral for 2-3 minutes and the temp dropped to 220 and I finished the climb, peaking again at 240. At no time did the engine have any trouble pulling the load; instead I was concerned about cooking my transmission.
We made a turn and I accelerated on a slight downhill until I could get 4th gear to lock up and as soon as that took place the temps dropped below 200 fairly quickly. Another 2 miles and we turned up the trail to our campsite and climbed 400' in about a mile at about 10-15 MPH and temps gradually climbed but didn't exceed 225.
I let it run for another 5 minutes while I backed the trailer in to the site and got situated. While there was plenty of heat pouring off the car nothing smelled hot. Bottom line here is that if you're not in 4th or 5th gear with the torque converter locked up then the transmission temp is going to climb above "normal". If the torque converter is locked up (only in 4th and 5th gears, right?) you can tow as fast and as long as you want with no rise in temp. How high the temp gets with the torque converter unlocked depends on how steep the grade is and how long you're running it (I'm sure ambient temps has an effect as well).
The next day my folks came along in their 4Runner (2008 V6 4x4 Limited) to Cerro Gordo. Here you climb from 3600' at Keeler, CA (old shore of Owens Lake) to 8200' in pretty short order. The first mile or two is a gentle climb out of the valley and then it turns in to a consistent steep grade for maybe an additional 5 miles. The trail is in good condition and has the typical broken rock, sand and dust that accompany many of the trails in the Mojave Desert and surrounding mountains. I drove the first section with the transfer case in 2H then switched to 4H about 1/3 of the way up. Transmission temps were in the 220-230 range through here (not towing anything). Then I went ahead and shifted to 4L and transmission temps stabilized but the grade increased some. Out of curiousity I switched back to 4H and was in 2nd gear and temps quickly climbed to 242 and showed no sign of stopping so I shifted back to 4L and the temp stabilized at 235-237 the remainder of the climb. Bottom line here was even though 4H was getting the job done, 4L was giving me a slightly cooler transmission temp.
I have plans to haul this trailer all over the Sierra Nevada and surrounding mountains with many destinations taking me through extended steep and slow grades back canyons, trails etc. so I am pretty much convinced I need to find a good way to keep my transmission from burning up.
Does anyone have good suggestions for a transmission cooling mod for this situation? Right now I think that an aux cooler in front of the radiator alone may not be enough. Will I need to add a cooling fan to it to get the performance I want, especially for slower speeds when airflow won't help to cool things as much?
Any suggestions?
By the way, I was very happy with the fuel economy while towing. I kept it at 55 MPH on the highways and averaged something like 17.6 MPG on the way up and 20.2 MPG on the way back. I had anticipated 15 MPG overall.
