Temp question

[supton]

This weekend I had stuff going on, and was running seemingly late for all of it, so I gave in and did what I've been wanting to do for a while: drive my truck like how I'd drive my car. You know, like at the speed limit (instead of trying to milk out every tenth of an mpg).

Before, for temps under 80F ambient, engine temp (off the Scangauge) indicated 180-185F, give or take, and 190-191 above 80F ambient. Now at 70mph it sits at 190-191 even at 60F ambient. No major surprise, engine works harder, and the thermostat does not have 0.1% load regulation.

The ATF reading I thought was more interesting. I'm 90% sure I have convertor outlet on the SG, the other temp sensor refuses to be read by the SG; the reading I get will drop in temp after convertor lockup within seconds. Again, at 60mph it will take forever to get up to 180F, and it will stay usually below water temp. But, at 70mph, even if it stays locked up for long periods of time, it will run a couple degrees warmer than water temp, like 194F.

I'm guessing that is from line pressure regulation in the transmission? Input shaft speed is higher, pump output is higher, but since x psi is still needed, it is just wasting that extra flow, hence warmer temp? I'm going from engine rpm of 1,500rpm to 1,900 or 2,000rpm, give or take a few mph.

[I'm not concerned, I just didn't think at 10mph speed increase would lead to a 10F trans temp increase. I don't know what temp the thermostat on the trans cooler operates at.]

 

[SHOZ]

With the converter locked up there is no "wasting" of power by the converter churning. It is direct lockup. It will run cooler than if it was not locked up by far. I would suspect air flow as the reason you see higher temps at higher speeds.

Do you have an electric fan or a belt driven one?

 

[supton]

Belt fan, on some sort of thermostatically controlled clutch.

Extra airflow at higher speeds would argue for lower temps, no?

 

[SHOZ]

The higher speeds may actually reduce air flow depending on the design of the front end. The fan may actually be impeding air flow too at higher road speeds. Most electric fans don't run at all over 30 mph.

 

[SHOZ]

Then again what you are seeing may be completely normal if you have not driven it at the higher speeds and monitored the temps in the past. I don't think either temp readings are not within the normal range.

 

[440Magnum]

I suspect the trans actually raises its line pressure in proportion to throttle position, so that's why you're seeing higher temps at higher speeds even with the convertor locked in both cases. higher pressure => greater shearing dissipation. Plus there's more friction at the gears and bearings, but I would guesstimate that is a lesser factor.

Also I'd say the numbers you're seeing are perfectly normal.

 

[asand1]

A 2010 Tundra should have a 200*+ thermostat.
190 has been normal for 20+ years. Transmissions run even hotter.

 

[meep]

my 06 tundra just won't go over 150F (casing temp) unless I'm towing. If the A/C is on it may fudge up 5F higher. When towing, 170F is pretty normal for 55-60 mph, level ground, 80F ambient. And by towing, I mean 90% of it's rated capacity. It will hit 220F on the rough hill climbs-- the 2nd or 3rd gear, 3500 rpm up-the-hill kind of climb. It settles back down 15 minutes later.

I have suspected the cooler starts to crack open around 180F based on watching line temps as it loads up.

electric gauge with sender mounted in the casing, 1" behind the sump.

Amsoil in the trans. It gets worked pretty hard during camping season.

 

[SwampSurvivor]

Are you sure it doesn't have a stuck thermostat? It really should be getting above 180 ...

 

[supton]

Originally Posted By: asand1
A 2010 Tundra should have a 200*+ thermostat.
190 has been normal for 20+ years.


I don't understand your two statements. One says it should be >200F, the other indicates 190F.

From what I can tell, I have a 185F thermostat. Whether or not it's still opening at 185 is a different story; at 100k I'll likely change the coolant, maybe the hoses, and if I do hoses then I'll likely change thermostat too. Maybe the water pump too at that time.

*

The temp doesn't bother me. The absolute #'s don't bother. The ATF going from less than water temp to greater than water temp--again, doesn't bother me. That it does this "trick" I thought was interesting, and I was curious if it could be explained, for the ATF, which is doing nothing (convertor locked the whole time).

 

[supton]

Originally Posted By: Miller88
Are you sure it doesn't have a stuck thermostat? It really should be getting above 180 ...


I think he is referring to the trans temp, not water temp. I don't know much about the prior Tundra; I'd think it too has a thermostat on the ATF cooler loop. But being on the case I'm not sure it's completely the same temp #'s as what I'm seeing: I'm taking readings from a sensor in the oil (someplace), his readings could be filtered, if it's case temp--it won't see the high mometary temps from momentary unlocked convertor.

 

[Lyman]

You couldn't just drive the thing could you? Had to get all BITOG about it.

Sounds like normal temps to me.

 

[meep]

Yes--- trans temp above--

 

[CBR.worm]

I see similar behavior in my FX. At 60mph the transmission will stabilize at the coolant temp which is about 185. At 82 mph the coolant temp will be about 190 and the ATF if the pan will be ~200 ATF going to the cooler will be ~206.

In both cases the TC is locked. What is interesting to me is that if the TC is locked in top gear while towing a trailer, the ATF will be cooler in top gear than 4th at any given highway speed. If the TC is unlocked, temperature quickly jumps.