Minimum operating temperature of transmission?

[ClydesdaleKevin]

Hey guys...what's the minimum safe operating temperature for our transmissions?  After all the cooling mods I did, my temp gauge reads around 110 degrees on average and rarely gets over 150 degrees...200 degrees max on the steepest mountain road.

Just want to make sure I'm not overcooling the transmission.

Thanks!

Kev

[cncsparky]

What kind of cooling mods did you do?  What temp was it running before?  Where is your temp probe?  Sorry for all the Qs  

[Oz]

I've noticed that most transmission temperature gauges start at 140° but don't show a low temperature zone.

Here's some info I found on digi-panel.com:
 

OIL TEMPERATURE MEASURED AT CONVERTER OUTLET TO COOLER:

300° F=  The maximum allowable temperature. This is the recommended place to install a temperature gauge or sensor. Do not allow the converter outlet temperature to exceed 300° F. The temperature at this location will vary significantly because of load, hill climbing, etceteras. If the temperature reaches 300° F, reduce throttle.  To lower transmission temperature with transmission in neutral, run the engine at 1,200 RPM for at least 2 - 3 minutes while keeping a close check for signs of engine overheating. A transmission in a heavy throttle, stall condition (a typical situation is rocking a vehicle stuck in mud, sand, or snow), may increase temperature at a rate of 1° degree per second of stall.   
 

OIL TEMPERATURE MEASURED AT OIL PAN OR SUMP:

150° F=  The minimum operating temperature.
Note: It is possible in low ambient temperatures to overcool the transmission with auxiliary oil to air coolers. Oil to water coolers in standard factory radiators will normally not overcool a transmission.

175-200° F =  Normal pan oil temperature operating range.
275° F =  Maximum allowable oil pan temperature for short durations during long hill climbs.
300° F =  Damage occurs to internal transmission parts, including warpage of metal parts, degradation of clutches, and melting of seals. Transmission oil oxidizes, (forming varnish-like substances causing further clutch slippage and compounding heat build up) and transmission oil life is extremely short.
 
 

AUTOMATIC TRANSMISSION FLUID LIFE / TEMPERATURE RELATIONSHIP:

Automatic transmission oil can provide up to 100,000 miles of service before oxidation requires replacement, at an operating temperature of 175° F. Above this temperature, the oil oxidation rate doubles with each 20° degrees F increase in oil temperature.

Note: Transmission oil and filter should always be changed more frequently when driving with heavy loads (RVs), typically at least every 25,000 mile intervals, since converter outlet temperatures then normally far exceed the ideal 175° F.

[ClydesdaleKevin]

That certainly helps.  I installed an additional cooler and fan in tandem to the original stock unit...which runs to the radiator first and then to the coolers and fans...and then back to the transmission.  Not sure where Holiday Rambler put the sensor.

Typically my temps are right around 110-150 degrees on the gauge, but not sure how accurate it is.  I haven't exceeded 200 degrees since doing all this, although I'll let you all know the hottest she gets on some of the big mountain climbs we have coming up soon.

Kev

[gary19734]

Derale makes a fluid control thermostat bypasses cooler untill fluid reaches 180 degrees also run amsoil trans fluid your transmission will love you for it Gary

[ClydesdaleKevin]

I think you can see the fan set up in this picture...the lower cooler and fan is the new one, added in tandem to the stock cooler and fans on top.





You can just see the top of the new fan sticking out over the bumper...its sits in front of a larger than stock cooler.  Its blocked from full air flow by the bumper, although it gets some from the lower air scoop. 


I have them wired into a toggle switch on the dash board...that way if I'm climbing a very steep grade in hot weather and I notice the temp gauge climbing, I can hit the switch, all the fans come on, and the temp drops immediately.  They don't come on by themselves that I've ever observed since owning the RV.


Kev

[ClydesdaleKevin]

Here are a couple more pics of the fan and cooler setup...I ran then through a relay...the switch on the dash energizes the relay.








Kev

[gary19734]

400 turbos biggest problem is they push too much line pressure back on the torque converter untill they warm up.They dont have a bypass valve like the 350 turbo does.This puts alot of pressure on the crank that tears things up thats why im suggesting the bypass thermostat want to get it warmed up as quick as possible   Gary

[ClydesdaleKevin]

The one on top is the stock OEM trans cooler.  The one on the bottom has the same size tubing as the stock one, but its larger (been in place for over a year, so I don't think its gonna hurt the transmission any).  We pull some massive hills at times out west, so this was a necessity...especially coming back east when its hot outside.  I will check to make sure the transmission outlet line goes to the fans first and then to the radiator and then back to the transmission to prevent over cooling.  I'm pretty sure that is the way its set up anyways, but will double check.  When I fixed all my dash wiring and grounds, the "normal" reading on all my gauges changed.  Fuel gauge stayed the same in function, but the trans temp dropped, the oil pressure dropped, water temp dropped, and the volt meter went up.  Just getting a handle on all the new readings so I can make sure I'm always running in an acceptable zone.


Kev

[gary19734]

By the way nice ride checked out the pics have to get some of mine on here.Just making suggestions hate to here about preventitive measures going wrong Been there done that way too many times   Gary