Automatic transmission temp?

[muskie hunter]

while towing yesterday, my Yukon's transmission temp reachd 180 degrees. This is with a factory installed tow package. I then installed a trans temp gauge and a secondary cooler.This gives me the radiator and 2 separate trans coolers.
Outside temperature was 70 with some stop and go traffic. I ran the truck mostly in drive instead of OD,but I did run in OD on the freeway with no gear hunting whatsoever. Is 180 to hot?

 

[tashasdaddy]

Re: Automatic transmission temp?

stay out of overdrive. just spent $3500 on a trans, did not know she had been pulling the trailers in overdrive.

 

[Gary H NC]

Re: Automatic transmission temp?

180 is not unreasonable.Your oil temp is close to the engine temp of 195 so i doubt 180 on the trans is a problem at all.

 

[guy74]

Re: Automatic transmission temp?

take a look at this: http://www.txchange.com/heatchrt.htm

 

[Silvertip]

Re: Automatic transmission temp?

No! 180 is not too hot. What causes transmission heat is excessive shifting and excessive torque converter locking and unlocking and long periods of hard pull with the TC unlocked. Transmission heat builds quickly when the torque converter is unlocked as it might be on a long grade. Many people feel that TC locking and unlocking is actually a gear shift when it is not. With the converter locked, there is no slippage in the tranny so heat build up is not an issue so the key is not whether to tow in OD or Direct, but knowing when its ok to tow in OD or Direct. Load, terrain, and traffic conditions determine that.

 

[Mkos1980]

Re: Automatic transmission temp?

I've been towing in OD (Highway only) for the last couple of years but then again the truck never downshifts or goes unlocked to lock. Usually flat. Usually stays 65MPH at 2500 RPM. With it in D I'm pushing 3300 RPM. But on the streets or where the MPH is 50 it stays in D. Lot of people will say with the size boat I have and a Ford ranger it should struggle, but it seems that with the 4.10's and towing 65-70 when permitted the rpms are high in the power band already meaning I never have to downshift to go up some hills. BTW to answer the question 180 is not hot. My factory guage in my 07 Grand Prix shows 176* alll the time when on the highway or normal driving. Now get it in traffic on a 100* day then it'll hit 215 or so. With the truck, I run the stock factory cooler and an autometer guage and the hottest I've seen it besides traffic is about 190ish going up hills but usually 180 cruising.

 

[SooLineRob]

Re: Automatic transmission temp?

180 degrees Fahrenheit is fine for an automatic transmission.

Keep in mind, factory cooling is done by plumbing the trans fluid through the radiator ... that way the fluid temp is regulated; not too hot nor not too cool. Frequent shifting/slippage/sitting still in gear with your foot on the brake pedal/lock-unlocking of the torque converter will create lots of heat, and the standard radiator set-up can't keep up. Also, too cold is no good either. You don't want your trans fluid at 100 all the time either.

I have a trans fluid temp gauge installed on 2 high(er) performance vehicles; a truck and a car. Both stay around 170-200 under normal conditions (just like the water temp!). The truck will heat up when slogging through mud; the car will heat up sitting in traffic. The "heat chart" linked above shows what happens for every 25 degrees of heat increase; I seem to recall the "beginning of the end" for trans fluid being 220 degrees. Transmissions can survive a spike up to 275, just get your fluid changed right away afterwards.

Engine oil has different properties and can withstand higher temps. I usually see around 225 on the highway on the oil temp gauges ... and after a full throttle stab into the gas pedal, 280 is not unusual...

As long as your trans fluid stays close to your water temp, the cooling system is working fine. And if the temp does spike up, remember to have the fluid changed right away.

 

[reelfishin]

Re: Automatic transmission temp?

180 degrees is probably the norm for many auto transmissions, but the cooler you can keep it, the longer it will last. I've rebuilt transmissions for 20+ years and a rule of thumb when setting up a trans and cooler is to shoot for the 150 degree running range with say about 175-180 on the high side with a large fan cooled trans cooler.
I'd be more concerned if there was a huge difference between loaded and unloaded temps, say for instance that running down the road empty you read 155 degrees F, but when you hook up a trailer and hit some hills you start seeing 200 degrees.
On my last full size truck I was able to maintain no more than about 140 degrees on even a hot day with a huge cooler, bypassing the factory radiator cooler, and a thermostatic electric fan on the trans cooler. The truck towed daily with no problems for over 170,000 miles.

Overloading, hard driving, poor trans condition, slipping torque converter, higher outdoor temps, and hills all can contribute to a trans running hotter than normal. You have to get to know your vehicle and what is normal before deciding you have a problem. Most newer vehicles will also trip an OBDII fault code and a check engine or trans light with any signs of slippage or excess heat. Many will also default to a single gear till the problem is fixed or cleared.

 

[jeeperman]

Re: Automatic transmission temp?

As long as the radiator trans cooler is in the curcuit, the engine will keep the trans. at engine operating temp.
Adding more external trans coolers to that circuit will do little to cool the trans. but it will help cool the engine.

 

[friendly_jacek]

Re: Automatic transmission temp?

As long as the radiator trans cooler is in the curcuit, the engine will keep the trans. at engine operating temp.
Adding more external trans coolers to that circuit will do little to cool the trans. but it will help cool the engine.

This is why the external coolers are put AFTER the radiator cooler and not vice versa.

 

[fishmen111]

Re: Automatic transmission temp?

180 degrees is probably the norm for many auto transmissions, but the cooler you can keep it, the longer it will last.

Could not agree more. While I do run through the radiator first for primary cooling, my secondary cooler is for a 40k GVW vehicle keeping it well below 160. I have gotten 200k miles out of some trannys with very bad reps.

 

[muskie hunter]

Re: Automatic transmission temp?

Could not agree more. While I do run through the radiator first for primary cooling, my secondary cooler is for a 40k GVW vehicle keeping it well below 160. I have gotten 200k miles out of some trannys with very bad reps.

I added an extra cooler. So. The trans fluid runs through the radiator then to the 1st cooler then to the second cooler then back to the transmission. Even at that the trans will see 180 on the gauge. I installed Hypertech to firm up the shifts also.

 

[fishmen111]

Re: Automatic transmission temp?

180 should be fine. I forgot to add that I also run an aftermarket 4-core radiator, aftermarket fan assembly and 160 thermostat in the summer which helps also. Mine will go above 180 under certain circumstances though.

 

[Rancherlee]

Re: Automatic transmission temp?

Over 170*+ is bad for the tranny AND extra coolers should be installed BEFORE it runs through the radiator if you do any cool climate driving. The factory cooler in your radiator is on the COOL side of the radiator which hardly ever gets above 150* (unless your radiator is full of crap). Anywhere between 100*-170* is ideal for your tranny.

 

[dave11]

Re: Automatic transmission temp?

The temp is OK. Shifting between D and OD will keep it OK.

 

[friendly_jacek]

Re: Automatic transmission temp?

Over 170*+ is bad for the tranny AND extra coolers should be installed BEFORE it runs through the radiator if you do any cool climate driving. The factory cooler in your radiator is on the COOL side of the radiator which hardly ever gets above 150*

Unless you drive in a 90-100F day (which is everyday during summer here) with A/C on and long uphill.

I agree with the part on cold climate and no need for extra coolers.
However, newer coolers go in a bypass mode when cold.

 

[Captain Caveman]

Re: Automatic transmission temp?

So do I need to haul my 16' boat and/or my snowmobile trailer with the overdrive off? I just put my Ranger in 'Drive' and go (the Ranger is a 4.0L with 3.73 axel ratio and 4x4). I've got the towing package and tranny cooler.

I've noticed that if I tow with the cruise control on, the truck shifts gears while going up hills. If I drive with my foot on the pedal, it never shifts gears.

Should I do anything different?