Just recently got the 4Runner back on the road and on just a short trip 35 miles, flat level highway @ 65 mph, 40F outside temp, Cruise off, ECT off and OD off, the "AT high temp light" comes on. The truck shifts and accelerates better than it has in years. Any ideas???

A340H rebuilt just installed 178 miles ago, new fluids, Toyota transmission cooler, fluid level and color good, no codes.

 

OD off @ 65 for 35 miles pushing 33's could do that. I have an aux. tranny cooler and if I did that I would definately be pushing at least 230degrees maybe more on my gauge. Once OD kicks in, the temp drops off real fast.

 

when highway driving at any speed over 45mph always have your OD on! It lowers your RPM's significantly. How many rpm's were you spinning at 65mph? My stuck-open egr valve caused my Torque converter to not lock up leaving me at almost 4k rpms at 80mph. My light came on after about 30 minutes of driving at this many rpms. its simply too much.

 

OD off means no TC lockup. That is most likely why it overheated.

 

OD off? You should probably keep the Over Drive on when you are driving at high speeds. You were probably revving pretty high when you had the overdrive off which might have caused your transmission to run a little harder.

 

I guess my question would be why was the OD turned off?

 

If i were you I'd keep OD on. I always keep my OD on, unless I'm going up a hill on a long road trip at high speeds.

 

OD off means no 4th gear and TC lockup... try driving with it off then press it on and it will shift once and the TC will lock

 

At 65mph she's running 3600 RPM's, sure I typically use OD on the highway for a long cruise but 35 miles is more of a sprint. I could understand pushing over 4K, but at 3.6K on a flat open highway your just rolling along. There's got to be a better reason, been runnig that small stretch of highway for 10 years without the OD and have never had the temp light even blink.

 

Sorry to say, thats just dumb. More wear and tear and gas...To each their own I guess.

 

Install a temp gauge and you will see that 35 miles is no sprint. I can be cruising in OD at 65mph and my gauge will be sitting at 135, if I turn OD off that gauge starts to climb real quick. In less than a minute, I can be at 190 or better easy with it still climbing! Now my temp gauge is reading the hottest temp of the fluid before it hits any of the coolers and like I said I have a big aux cooler. Once I turn OD back on, the temp will fall pretty fast. Now imagine running like that for 35 miles! I don't know if your cooler can keep up with that type of temps for that long. Also, let it be said that I have never had any tranny problems, so I can't imagine what the temp has to be to turn the light on.

 

I can't agree on the "dumb" comment, mainly because OD is for sustained highway speeds and on this stretch of road unfortunatly your lucky to have an average speed of 50. The speed limit is 65 but I don't believe OD was designed to assist the tranny jumping from 45 to 65 and back over a distance that small. I would think it would be as bad as leaving it in OD in town. Correct me if I'm wrong, I don't think i'm dumb but it's possible i'm uninformed.

 

Do trannys have any type of "break in" period like a rebuilt motor would? If so, OD off, those rpms, pushing 33's, and for that long?!!! That may be the problem.

 

Thanks slosurfer, that does make some sense and the temp gauge is a great idea. now could someone provide some insight on OD with constant highway speed vs varible speed.

 

The difference between the two is easy to see when you have a gauge, but I will try to explain. If you are at a stop light and get on the gas, you can watch your temp rise faster than your mph, but then eventually you level off once you get to the speed you want and are off the gas some, then your temp comes down some and levels off. On the highway w/ those rpms, your temp is doing the same thing, but has no chance to level off or cool. If it does level off, it is at a really high temp. At those speeds, the only way it is going to cool, is when OD kicks in.

 

I don't know about a break in period, my concern is that the reason for OD is an additional gear for "maintained" highway speed. Should I use OD at an inconsistant highway speed, wouldn't it be like not down/up shifting with a standard, wouldn't your fuel savings be tossed anyway?

 

what gears are you running? 5.29's would prolly make it a bit easier to drive in overdrive at highway speeds.

I'm currently cursed with 4.56 stockers with 31s, and it's HORRIBLE. 5.29's go in sunday, but i'm thinkin gears and a good cooler could help you a lot.

 

Trannys now days are designed to be left in od even around town. Thats what I was told by a toyota master tech that I used to work with.

 

4.88's chimmike, the re-gearing is on the wish list

 

OD in town? I would think they wouldn't even call it OD and reconfigure the shift points. How about some Tech input, I definatily don't want to risk a toasted slush box.