BE4Runner
New member
We are about one month and 7,000 miles in to our tour of the US in our 2000 4Runner 2WD, and I've started having what I think are overheating issues with the transmission.
A couple days ago, I pulled out my monitoring phone (OBD II Bluetooth adapter + Torque Pro on an Android phone) on the highway, and saw that the transmission fluid was hitting 230 degrees F on long, gradual uphills. I discovered if I could prevent the engine from having to rev at all, meaning cruising at 2,000 rpms, the temp would stay in control (under 200 degrees F). I can cruise at around 50 with overdrive off or 65-70 with overdrive on. If I push beyond that the transmission slowly heats up to 230 degrees F and sometimes higher.
Yesterday we were driving in Big Bend NP, a slow, steep, winding road, and the transmission temperature kept rising and rising until it hit 250 degrees F. I pulled over and waited for it to cool down a bit before continuing. This seems way high to me.
The fluid level still looks right - when warm, I cycle through the gears, and the dipstick is showing smack dab in the middle of the hot lines. Fluid was changed about 20,000 miles ago. When I start the truck in the morning, transmission temp looks basically like ambient air temp, so I don't want to blame the sensor. I don't have an external transmission cooler, and the Denso radiator has about 25,000 miles on it. Engine coolant is mostly stable between 176-185. Note that about 2,000 miles back I rolled the 4Runner on Vail Pass in CO. It was turned off immediately, sat on its side for about 45 minutes, then flipped upright and towed back into town. We added some oil and coolant back in, trans fluid level looked good. I monitored temps when we drove it back over the pass and everything looked fine.
I'm not sure what to look for to see why it is overheating. Any ideas?
A couple days ago, I pulled out my monitoring phone (OBD II Bluetooth adapter + Torque Pro on an Android phone) on the highway, and saw that the transmission fluid was hitting 230 degrees F on long, gradual uphills. I discovered if I could prevent the engine from having to rev at all, meaning cruising at 2,000 rpms, the temp would stay in control (under 200 degrees F). I can cruise at around 50 with overdrive off or 65-70 with overdrive on. If I push beyond that the transmission slowly heats up to 230 degrees F and sometimes higher.
Yesterday we were driving in Big Bend NP, a slow, steep, winding road, and the transmission temperature kept rising and rising until it hit 250 degrees F. I pulled over and waited for it to cool down a bit before continuing. This seems way high to me.
The fluid level still looks right - when warm, I cycle through the gears, and the dipstick is showing smack dab in the middle of the hot lines. Fluid was changed about 20,000 miles ago. When I start the truck in the morning, transmission temp looks basically like ambient air temp, so I don't want to blame the sensor. I don't have an external transmission cooler, and the Denso radiator has about 25,000 miles on it. Engine coolant is mostly stable between 176-185. Note that about 2,000 miles back I rolled the 4Runner on Vail Pass in CO. It was turned off immediately, sat on its side for about 45 minutes, then flipped upright and towed back into town. We added some oil and coolant back in, trans fluid level looked good. I monitored temps when we drove it back over the pass and everything looked fine.
I'm not sure what to look for to see why it is overheating. Any ideas?
