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-   -   Tranny Temperatures? (https://www.irv2.com/forums/f45/tranny-temperatures-30328.html)

sawtooth 03-09-2006 09:36 AM

Last fall replaced my old RamCharger (RC) with a newer vehicle to pull my new travel trailer. The old RC has a short wheelbase, high center of gravity, too many miles and semis blew it all over the road when passing going 80 MPH.

The Trailer: '05, Fleetwood, Pioneer; 22', advertised dry WT. 3,647 LBS, actual WT. 5200 LBS with our extras (air, awning, ETC), dry tanks (gray, black, & water), and all our stuff.

The Truck: "96 Dodge 1500 (1/2 ton), 4X4,5.9L (360), 3 SPD. Auto with overdrive, and lock-up torque converter, 3.55 DIF, (oversized tires give a gear ratio of 3.22), GCWR 12,500, and Max Trailer Wt. 7,700. Tranny fluid flow on this vehicle is torque convert output to radiator, radiator to tranny cooler (mounted fwd of radiator) and then to the tranny pan.

After reading about all the troubles Dodge & other manufactures have had with auto trannys since they stopped using whale oil, I sought the advice of some experienced RV'ers. One fellow, who has made a couple of 360 DEG trips to Alaska, told me to keep the torque converter in lock when ever possible to reduce heat. Another fellow told me to install a temp. gage at the output of the torque converter and drive for the lowest temp.. So I pulled the tranny pan, installed a drain valve, & a new filter. 200 miles later, drained the tranny fluid and refilled. Installed an oil temp. sensor VIA a T-fitting between the torque converter output and the radiator. (tested the gage and sensor in boiling water to determine accuracy).

Our trip: Boise to Glenns Ferry, ID, freeway, tranny temp was 140 on the flats but hit 220 on some 6% grades before I dropped into 2'nd. Glenns Ferry to Stanley,ID, temp reached 250 about 1/3 up Galina Pass (8700ft) dropped into 1'st and temp decreased to 210 before the summit. ( the torque curves on this truck are relatively flat between 2000 and 4800 RPMs, my max rpm is around 3500). Stanley to Salmon,ID, temp never reached 140, stopped to trouble-shoot gage and then realized following the Salmon River East was down hill. Salmon to Darby, MT, 8500 ft pass same results as Galina.

My scheme of increasing RPMs , keeping a lot of transmission fluid flow worked well until we reached Lewiston, ID (750f). Pulling out of that area the temp gage hit 230, dropped to 2'nd( temp gage 240), dropped to 1'st (temp gage 250), the radiator temp gage approached 230 (normal is 200). Dropped to 4-low and temp readings seem to hold until we found a turn-out.

So how do you fellows keep your tranny cool?
Does tranny fluid start to varnish and lose its lubricating properties at high temperatures?
Should I remove the gage and drive pedal to the metal which seems to be the norm?

sawtooth 03-09-2006 09:36 AM

Last fall replaced my old RamCharger (RC) with a newer vehicle to pull my new travel trailer. The old RC has a short wheelbase, high center of gravity, too many miles and semis blew it all over the road when passing going 80 MPH.

The Trailer: '05, Fleetwood, Pioneer; 22', advertised dry WT. 3,647 LBS, actual WT. 5200 LBS with our extras (air, awning, ETC), dry tanks (gray, black, & water), and all our stuff.

The Truck: "96 Dodge 1500 (1/2 ton), 4X4,5.9L (360), 3 SPD. Auto with overdrive, and lock-up torque converter, 3.55 DIF, (oversized tires give a gear ratio of 3.22), GCWR 12,500, and Max Trailer Wt. 7,700. Tranny fluid flow on this vehicle is torque convert output to radiator, radiator to tranny cooler (mounted fwd of radiator) and then to the tranny pan.

After reading about all the troubles Dodge & other manufactures have had with auto trannys since they stopped using whale oil, I sought the advice of some experienced RV'ers. One fellow, who has made a couple of 360 DEG trips to Alaska, told me to keep the torque converter in lock when ever possible to reduce heat. Another fellow told me to install a temp. gage at the output of the torque converter and drive for the lowest temp.. So I pulled the tranny pan, installed a drain valve, & a new filter. 200 miles later, drained the tranny fluid and refilled. Installed an oil temp. sensor VIA a T-fitting between the torque converter output and the radiator. (tested the gage and sensor in boiling water to determine accuracy).

Our trip: Boise to Glenns Ferry, ID, freeway, tranny temp was 140 on the flats but hit 220 on some 6% grades before I dropped into 2'nd. Glenns Ferry to Stanley,ID, temp reached 250 about 1/3 up Galina Pass (8700ft) dropped into 1'st and temp decreased to 210 before the summit. ( the torque curves on this truck are relatively flat between 2000 and 4800 RPMs, my max rpm is around 3500). Stanley to Salmon,ID, temp never reached 140, stopped to trouble-shoot gage and then realized following the Salmon River East was down hill. Salmon to Darby, MT, 8500 ft pass same results as Galina.

My scheme of increasing RPMs , keeping a lot of transmission fluid flow worked well until we reached Lewiston, ID (750f). Pulling out of that area the temp gage hit 230, dropped to 2'nd( temp gage 240), dropped to 1'st (temp gage 250), the radiator temp gage approached 230 (normal is 200). Dropped to 4-low and temp readings seem to hold until we found a turn-out.

So how do you fellows keep your tranny cool?
Does tranny fluid start to varnish and lose its lubricating properties at high temperatures?
Should I remove the gage and drive pedal to the metal which seems to be the norm?

sawtooth 03-09-2006 10:08 AM

Woa is me!
I thought I was in the trailer section.

Fyrflie 03-10-2006 06:59 AM

Seems like the biggest problem is your overall gear ratio.

Overall temps., considering the country you were in, are probably okay.

Do a search on tranny temps. and you will find that most damage doesn't occur until the 300 deg. range. But of course, any temp above normal for extended periods will result in some sort of damage.

How about cooler size. Is it matched to the load you are pulling?

aragu36 08-26-2008 09:43 PM

synthetic oil is what allison dealer told me to help cool oil temp the only differance is 5 gallons of atf is $50-75 syn $200 5 gal

aragu36 08-26-2008 09:45 PM

SORRY NOT THE ONLY DIFFERANCE ATF BOILS AT A LOWER TEMP

blacktie.shooter 08-27-2008 06:46 AM

To save your tranny, you've got to beat the heat. One website (can't find it now) published a chart, that basically said if your tranny temp gets over 250 for anything over a short length of time, it will soon be toast. I don't know how accurate, I have never heard "until 300...," but it was enough to scare me.

I switched to full synthetic, and here is why: pulling a grade out of the Columbia River Gorge, with dinosaur oil in the engine, temp gauge went from 190 to 235 or so. Switched engine to full syn, pulled same grade, temp went up about 4 degrees. As soon as I got home, I switched the tranny to Mobil 1 for Mercon, and specifically because I was going to start towing a toad. Don't have a tranny temp gauge, but whatever I have reduced the tranny heat by has got to be a good thing.

If anyone thinks full synthetic is expensive, try having the transmission pulled, rebuilt, and reinstalled.

Best of luck to you.

JimmyDee 08-27-2008 03:58 PM

Synthetic oil has a breakdown temp that is 100F higher than dino oil. Usually when we are monitoring tranny temps, it is in the pan. Temps in the internals of a tranny are much higher than the pan temps. 250 degrees in the pan could put the internal oil temps way over what is safe for dino oil and it is turning to varnish. Synthetic is far less seceptable to burning or varnishing.
Jim

Joe-K 08-28-2008 08:15 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by sawtooth:
Woa is me!
I thought I was in the trailer section. </div></BLOCKQUOTE>

No Problem https://irv2.infopop.cc/images/thumb.gif
Moved to Trailer Towing section for you.

Joe


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