Scan gage set for transmission temp, now what?

[CarlB]

just running a short highway stint this afternoon, I saw a high of 190ish. What is an acceptable range and when do I need to pull over and let her cool off?

[lx22f/c]

I was told by a transmission shop to never let it get to 220 degrees

[tugboat95]

Depends on your brand and model. But generally cooler is better. Much over 225 and most fluids start to breakdown. My suburban stays between 170 and 190 most of the time. I have seen 210. My Escape though stays between 190 and 210. I have seen 220. Both of these are dependant on load and weather temps, etc. To get brand and model specifics you can find info on the web or contact a local dealer. With my 2 vehicles I can watch the temps and see when the thermostat opens and closes on the coolers. It never stays on the high end for long. My Escape runs everything hotter. My coolant temp normal is 212 to 215. But under increased pressure this is normal.

[Jmooney]

The chart above provides a graphic illustration of just how devastating excessive heat is to the life expectancy of an automatic transmission. The general rule of thumb is that for each 20 to 25 degree increase in temperature the transmission's life expectancy is cut in half. Keeping your transmission cool is the key to longevity.

Transmission and Transaxle
Heat Temperature Failure Chart
175 Degrees: 100,000+ miles (Normal is typically 179 to 195 degrees)
200 Degrees: 90,000 miles
225 Degrees: 55,000 miles (Pressure Drops)
250 Degrees: 25,000 miles (Valves Stick)
275 Degrees: 17,000 miles (Varnish Forms)
300 Degrees: 4,000 miles (Seals & Clutches Burn)
325 Degrees: TRANSMISSION FAILURE

[havnfun]

Nice chart, Jim. It puts it all out front for us to see (and worry?).
Does it help if you change tranny fluid more often than the manual states?
Happy RVing,
Jeff

[djtho1]

Personally, I will have the transmission fluid changed every time it gets hot. For awhile, that was two to three times per year when I was pulling with a ford van in WVA. It would see 250 on long climbs in second gear. I noticed that once the fluid got hot once that the temp never seemed to stay down after that. Expensive on the frequent changes, but I have a stock Ford 4R100 with 156,000 trouble free miles behind a tuned 7.3 (knock on wood). I would change it any time it has been hot.

[Jmooney]

My understanding is that if you get up into the 200+ range, that the fluid viscosity deteriorates and looses effectiveness, so,yes, replacing becomes critical.

[djtho1]

Agreed Jmooney. That is my understanding as well

[Jmooney]

Originally Posted by havnfun

Nice chart, Jim. It puts it all out front for us to see (and worry?).
Does it help if you change tranny fluid more often than the manual states?
Happy RVing,
Jeff

I shouldn't take credit for this, I pulled it from a tranny website

[Jmooney]

Most HD trucks have transmission fluid coolers now. My 2015 Ram does, but I keep the tranny temp as a primary guage up on my display just in case.

[djtho1]

I added a 13x17 inch cooler to my 2002 power stroke van and saw a 20 degree drop on highway and more when pulling in the hills. My 2000 ford dually now has a custom built transmission and pulls our toy hauler at 165 to 175 degrees consistently without additional cooling. The custom built unit has Amsoil race fluid and the stock unit has regular fluid, no synthetic. I was told not to use synthetic in a stock 4R100.

[dsmith3]

Originally Posted by djtho1

Personally, I will have the transmission fluid changed every time it gets hot. For awhile, that was two to three times per year when I was pulling with a ford van in WVA. It would see 250 on long climbs in second gear. I noticed that once the fluid got hot once that the temp never seemed to stay down after that. Expensive on the frequent changes, but I have a stock Ford 4R100 with 156,000 trouble free miles behind a tuned 7.3 (knock on wood). I would change it any time it has been hot.

djtho1 - I tow a Flight 32BHDS with my 1999 7.3 Power Stroke. Recently upgraded my transmission cooler from the smallish stock 7.3L cooler to a much larger 6.0L cooler. Towed last weekend in the Hill Country and didn't get above 170 degrees (around town driving is around 150). Heading to Wyoming in July with family (Grand Tetons and Yellowstone NP). That'll be the real test.

[djtho1]

On the 2000 dually I also changed out the 7.3 cooler for the 6.0 cooler. I pulled a 32 bhds with our 2002 4x4 van with the 7.3 with no problem on the highways and with some elevated temps on the hills when I had to climb slow, but the temps came down quickly. With the truck I am pulling a seismic 3712 (about 19,000 lbs) and have not yet seen temps above 190. On highway it stays consistently at 165, and that was from Ohio to California. That is with the custom built tranny though. My stock unit ran warmer than that. Safe travels!

[dsmith3]

Amazing! That toy-hauler is a beast!

[Clayton4971]

I ran a scan gage on my 05 6.0 ford and I like to monitor coolant and oil temp. Usually a ten degree difference . This let me know of any failure in the system before anything burned up . They were known for EGR failure. Scan gage is a nice tool to have and can monitor a lot of engine functions

[CarlB]

speaking of fluid swaps, on my old sprinter based class c, they recommended flush and service of transmission at 50k. The guys at sprinter source said that most of the rigs with transmission issues at 70k, had used the factory specified service interval. Wonder what the average tranny temp was on those rigs.

[Swinepartner]

Glad I found this thread. My trans temp has been my biggest worry so far. On level ground and 60MPH, pulling about 7K, it averages 180ish. But when I slow down through towns, it creeps up to 190's to as high as 210 so far. But it's only been that high for 5 min and a few miles. My biggest fear is getting stuck in traffic due to construction or a wreck and having to creep for miles. My burb has the factory trans cooler installed, And I've only towed about 400 miles this year. Should I look at getting a larger trans cooler? Or am I good to go?

[tugboat95]

You should be ok. The temp will rise when there is no airflow over the cooler. You coolant temp also rises until your fan kicks on. As long As you are below 225 you're ok. If you are still worried though, instead of a cooler check and see if you can get a dedicated fan on your current cooler. Its all about the airflow. Oh and make sure the fins are clean on both side. Your temps sound right in line with what I see with my suburban.

[rryman]

That doesn't seem excessive to me, I came across a mountain last week with mine and I checked the temp at the top of a 7 mile grade and it was 209.

[Swinepartner]

Thanks y'all for easing my concerns.