transmission Temp ???? 48RE

[jrgough]

I just installed an transmission temp gauge in the hotline From Diesel manor. What should i see as far as readings for cruising,traffic hauling?

 

[Prairie Dog]

I always started worrying if it got much over 160 degrees. Much over that and the fluid starts to break.

EDIT - Opps, meant to say 260 degrees.

 

[cerberusiam]

Unloaded driving and light towing in lockup, the temps run 180-190 when the ambient is over 70 degrees. Under 70 degrees 160-170 is normal.



Heavy towing add 10 degrees.



Its not unusual to see 220 in stop and go traffic when the ambient is high or your towing. As long as the temp drops when it goes into lockup your good.



If you tried to tow your 5'er out of a camp spot on 12% grades at 25 mph and don't use manual gears, expect 300 degrees or better.



Same thing if you spend any time in high range trying to back heavy loads into tight spots or up hills.



The fluid\trans operating range is 140-240 degrees as long as you stay in that range and change the fluid every 30k the waranty is honored and the trans even lasts pretty decently for an NVH hobbled unit.

 

[goodguys75]

in vegas i run over 200 easy in mid summer. but goes down when i get on the freeway to about 165... . I also run a maghytech transmission pan with and extra quart... seems to help a little... .

 

[cerberusiam]

Much over that and the fluid starts to break.



EDIT - Opps, meant to say 260 degrees.

Actually the fluid is rated for much more than that for a long period. Transmission however suffers badly with extended temps that high. Seals tend to soften and tear, frictions unbond from the steel, etc.

 

[Yo Hoot]

The key is to force lockup as needed with a switch.

 

[BGlidewell]

not an expert, but I was told not to worry too much as long as you are not sustained over the coolant temp. Higher temps = more frequent transmission oil / coolant changes.

Empty I see less than 150 except in 100+ days which can burst to almost 200 in heavy traffic trying to keep the rat racers under control.

 

[Yo Hoot]

I see 300 pulling 8000 lbs up a steep grade. That's without the TC locked.

 

[BGlidewell]

this is also assuming you are measuring from the transmission towards the cooler.

 

[puller]

yo hoot



Is there any way you can force a TC lockup without installing a switch?



Puller

 

[WalterJ]

I believe the internal temp. sensor is inside the valve block of the 48RE, so it represents the "cooled" oil. Also, these new fluid formulations don't behave as the old school versions, ie; these modern trans fluids don't change color when 'burnt', nor do they have a 'burnt aroma' like the older fluids. I relied on those telltales as well, but now I'm 'blind'.

I can't find my source at this time, but I recall 240 trans temp (non synthetic) is considered 'normal maximum'. It starts degrading rapidly from there up. Check out this link Chrysler transmission fluids: 7176, ATF+3, ATF+4 for technical ATF-x discussions & references. I just had a Derale Hyper Cool Extreme installed on my 2004. 5 4x4 (SRW) 3500, because last Summer I experienced 230+ deg (internal valve block sensor) stuck in traffic going up hill (3%) for 90 minutes in PA. Coming from WI, I opted for the Cooler Bypass valve so as not to super cool my fluid in Winter.

 

[Yo Hoot]

No you cannot lock the TC without the switch.



My temp sensor is at the cooling line coming out of the TC. That's where you get the hottest reading. Some say that 300 is not a concern since in the pan and in the valve body it's not seeing those temps.



The fluid IS seeing those temps or I would not be reading them that high. 300 is pretty hard on fluid from everything I've read.



I no longer allow the fluid coming out of the TC to exceed 250.



I have control now.

 

[Bill Stockard]

No you cannot lock the TC without the switch.

My factory stock 48RE will lock the torque converter in either 3rd gear (OD turned off) or 4th (Overdrive) at speeds above about 45 MPH. It will lock up in 2nd gear around 25 if I shift to 2nd gear manually.



Bill

 

[Yo Hoot]

My factory stock 48RE will lock the torque converter in either 3rd gear (OD turned off) or 4th (Overdrive) at speeds above about 45 MPH. It will lock up in 2nd gear around 25 if I shift to 2nd gear manually.



Bill

Yes but you are at the whim of the computer. If you don't get out of first or don't exceed 25 in second, you get real hot.

 

[WalterJ]

Update to my recent Derale Hyper Cool Trans Cooler install. Curently traveling to SE Kentucky, I'm seeing confusing temperatures (small IR tool I use for chk'g tires & bearing hubs) resulting in no Derale cooling fan action. Is my OEM sensor bad? Banks PDA display bad? Whaat's up doc?

Trans pan - 176
Hot Trans out line - 156
OEM cooler return line at Trans (continues past transmission to aux cooler inlet) - 144
OEM sensor via ODB/Banks PDA port - 195
------------------------------------
Ambient - 66
Lube Oil pan - 192
14K# 5th Wheel = 21500 GCVW
60-65 MPH, Towhaul, Cruise Cntl.

 

[cerberusiam]

Looks pretty normal to me, nothing there to suggest the Derale is even needed. If the sensor is wired normally it generally won't come on until the return line temps exceed 180 degrees anyway and it looks like its not even close.



At an ambient under 70 degrees you have to work it hard to get the temps to even approach normal.

 

[Yo Hoot]

I would expect the hot line out to be higher than the pan but with the IR gun I'm a little skeptical of the readings. Don't forget the Derale is cooling even without the fan on and when you are doing 65 you are locked up most likely which brings temps down below the cooler fan threshold.



My real question is how you hold the IR gun on the trans while doing 65 :-laf

 

[WalterJ]

I'm a fast runner?

cerberusiam: Thanks for quick reply. When we pulled over at a rest stop & I jumped under truck for temp. readings. I held the IR 'gun' directly against the objects I was sensing. My puzzelment is the Banks PDA reading of 195! How does that fit into the picture relative to my IR readings? I agree that ignoring the 195 data, there's no problemo with the aux cooler.

Sorry, I'm bad: I forgot to mention that I have an "aux cooler bypass" thermo (180 deg) actuated valve installed to prevent supercooled ATF during Wisconsin Winters. This 4 port valve is open when seeing temps < 180, thus bypassing aux cooler; @ >180 this valve begins closing, thus routing ATF thru cooler. My Banks Tuner PDA is Version 2. 3, then they came out with another/updated display product.

I'm still hunting for actual OEM sensor placement in my 48RE transmission, and theory of how its temp relates to my other data. Safe travels.

Wally

 

[Yo Hoot]

I've replaced the OEM sensor. It's mounted to the valve body.



In this picture the Gov pressure/Temp sensor is the black unit hanging out on the left. It goes into that hole just to the right.



#ad

 

[cerberusiam]

My puzzelment is the Banks PDA reading of 195! How does that fit into the picture relative to my IR readings?



I'm still hunting for actual OEM sensor placement in my 48RE transmission, and theory of how its temp relates to my other data. Safe travels.

What you are seeing is the difference between radiated temp and actual temp in the fluid body or stream. Since the OE temp sensor is part of the gov pressure transducer, its immersed in the center of the fluid sump.



The same thing happens when your shooting lines, manifold, etc. The radiated heat is ONLY from the surface temp and than is always cooler than the center of any body of liquid or solid. The cooler outer layers act like an insulating blanket to trap the heat internally because only so much heat can be radiated from a finite surface area.



I am going to get booed and hissed for this but I have asbestos shorts so here goes. The IR guns have their place and uses but are not really a good indicator of actual temps. Temp differences from a standard yes, actual temp no. I call them a Buzz Lightyear Ray Gun when somebody tries to rely on their readings as a substitute for a probe in the stream of what is measured. Like I said, for surface temps differences they are fine but you need a comparitive to make sense of the readings. The error factor can run from 10% to 50% depending on the thermal conductivity and density of the material being IR'ed.



The difference of 175 IR to 195 OE sensor is perfectly normal and right in the operating range for what you were doing. Sump fluid is a mixture of lube\cooled fluid after is has gone thru the cooler then been used to lube thrusr washers, bearings, etc, AND (this is important) fluid used in the TC. for lockup and fluid coupling.



In fluid couling a lot higher percentage of fluid used in the TC is dumped directly to the sump to keep the volume available for use than when the TC clutch is locked.



You also have to remeber the data stream from the ECU that it is interpreting from the OE sensor has been interpolated to a degree and manipulated by routines in the ECU. In addtion, the signal is analog voltage to represent a temp value then is converted to digital for propogation to the data bus. Exact is not a word that can be assigned to the run of the mill sensors in these units, a large ball park is closer to the truth because of the potential variances and conversion errors.



Given what I have seen from monitors, if you had a probe in the same place as the OE sensor it would probably read 185. It all sounds well within the normal parameters and even on the low side given the ambients.



Drive. Be happy.