Transmission temp question

[alexanderJ]

2005 2wd 2500 CTD 125K miles. Excellent condition.

I need advice. My transmission is shifting fine and I'm having no issues except for noticing higher transmission oil temps when pulling my 5th wheel trailer. For many years I've noticed the temp as measured in the pan to reach 220-230 degrees for short periods of time when the converter is not locked up, i.e. pulling a grade or stop/start traffic. When pulling on flat grade temp will be about 100 degrees over ambient temp.

I don't live in an area where there are a lot of competent transmission shops, but I've had one that suggested a torque converter replacement should help the problem. I'm really hesitant to replace a working TC not knowing if a new one would help or that I might have even more issues with it not knowing the competency of the shop.

Based on above info would I be better off just trusting that my OEM TC is still somewhat reliable? Please give me some input.

 

[Ozymandias]

I don't see a problem here.

Is your transmission cooling system in factory condition?

Is the radiator stack free of debris and has full airflow through it?

 

[alexanderJ]

Yes Sir. Transmission cooling system is factory stock. I routinely inspect and clean radiator.

I completely flush/change the oil (18 qts) every 25K miles.

I've though about adding a deep pan, aluminum with fins, but from everything I've read this won't help much. I'm just trying to convince myself I've not weakened the transmission or TQ at these temps. It's kinda an "if it ain't broke" situation.

 

[Ozymandias]

No you didn't, the todays fully synthetic Trans fluids can run all day long at this temperature without breaking down.
And as you said most of the time you run at 160-180 which is the normal operating temperature.

 

[steve69]

How much weight is your 5r? It seems to me that you are ok. When I pull my 7k TT, on long grades in summer at 80plus. Like Monte Eagle. I will push around 200. Was told it was fine

 

[alexanderJ]

How much weight is your 5r? It seems to me that you are ok. When I pull my 7k TT, on long grades in summer at 80plus. Like Monte Eagle. I will push around 200. Was told it was fine

I'm probably around 9K loaded. I wouldn't have been concerned at 200 like you but when I hit 220-230 every now and then I get uneasy. Especially since the truck is 20 years old. I would just hate to be in the middle of nowhere and have the transmission or TQ crash.

However, based on Ozy's comments I'm feeling better.

 

[bigceltic]

I'm probably around 9K loaded. I wouldn't have been concerned at 200 like you but when I hit 220-230 every now and then I get uneasy. Especially since the truck is 20 years old. I would just hate to be in the middle of nowhere and have the transmission or TQ crash.

However, based on Ozy's comments I'm feeling better.

You may also look at a new trans cooler like the Mishimoto. Since replacing my stock cooler with the Mishimoto, I noticed I rarely go above 190 anymore, even towing up and down the CO mountains (9K trailer) in the summer. Super easy swap (at least for my '06).

 

[SSage]

Sounds normal to me. In the summer I see 195 to 210 pulling trailers on two lanes. Its rare to see 225 plus unless I'm backing up a hill. My old 48RE runs 165 to 175 in the pan on the interstate year round. All stock cooling system, but the trans has been rebuilt with Goerend parts. I love having the aftermarket sump pan, I think mine is from BD. I like the large drain plug better than the Mag-Hytec plug that uses a small Allen head plug in my other truck. The triple disc torque convertor is really strong, its so much better than stock.

 

[p-Bar]

Your fluid will start breaking down at that temp. I used to monitor mine as it came out of the TC . that's the hottest point. Reverse was the worst as the gearing was not low enough. I would hit your levels so yours is really cooking that fluid. We had many discussions on this 3rd gen forum back in the day. This trans is better than the 68rfe.

 

[alexanderJ]

Your fluid will start breaking down at that temp. I used to monitor mine as it came out of the TC . that's the hottest point. Reverse was the worst as the gearing was not low enough. I would hit your levels so yours is really cooking that fluid. We had many discussions on this 3rd gen forum back in the day. This trans is better than the 68rfe.

I've found very few threads on this issue. If you could link me to some of these discussions you mention I'd really appreciate it. After the mention above of the temp range of newer synthetic transmission fluids I did a little research and it appears that 220 - 230 is not that big of an issue. In fact one post in 2020 by @cerberusian stated "Operating range on a stock 48RE is 140-240 degrees, anything in that range should prove no problem if you follow fluid change rules."

 

[p-Bar]

I'm not sure how far back the archives go . Cerb was one who talked about it. You gotta be 20,30 + coming out of that TC. There is a check valve on the trans cooler that have been a problem at times and some guys drilled them out . Cerb would know about that too.

 

[steve69]

Are you using tow haul mode? And you're only seeing these temps when convertor is unlocked? 100 above ambient seems right.

 

[alexanderJ]

Are you using tow haul mode? And you're only seeing these temps when convertor is unlocked? 100 above ambient seems right.

Yes using tow haul, but on the '05 tow haul only changes the shift points. It cannot be used to lock out OD.

And yes, only seeing those temps when TC unlocked. At highway speeds in 4th gear TC locked all is fine.

 

[Ozymandias]

Again, no need to be worried.
Your system operates like it is designed for.

 

[alexanderJ]

Again, no need to be worried.
Your system operates like it is designed for.

Thank you. There appears to be lots of data on the web that supports that.

 

[Topzide]

@alexanderJ, Just keep an eye on your fluid. I like to check with white paper towel or napkin. That way, I can see the color of the fluid and look for debris on the dip stick. Modern fluids do handle heat way better than the fluids of our "youth". As @Ozymandias has stated, the system is working as it should, just keep up with fluid change schedule. The time factor for how long the fluid is in the transmission does play a part in when to replace. Once the heat cycles start, oils start to degrade.

Sounds like your concerned about what is taking place with your truck, that's a good thing! A little TLC, goes a long way to how many years that you can enjoy your truck! Keep doing what you've been doing!

 

[steve69]

What does your engine temp run when your transmission is running warmer.

 

[alexanderJ]

Sounds like your concerned about what is taking place with your truck, that's a good thing! A little TLC, goes a long way to how many years that you can enjoy your truck! Keep doing what you've been doing! :cool:

.

I am concerned, and considering the fact that the truck is 20 years old it is is extremely good condition inside and out. I'd just like to make sure it continues to be reliable for a few more years.

@steve69 Engine temp runs 190 to 200 degrees when towing, and doesn't seem to increase in relation to transmission fluid temp.