You may remember I have a 2005 5.9 TDC 4WD with Pacbrake exhaust brake and a BD cooldown timer. It has the 4Spd Auto Tranny with the tow package.

Okay another set of rookie question:

What is the safe operating temprature range for the Dodge Ram 5.9 CTD 4 Spd auto tranny?

Which side should the temp be measured on duty or return?

What is the highest allowable temprature when towing 8000#s up a 7% grade?

What effect does enegaging the exhaust brake (when coming down a steep grade) have on tranny temp?

Is there a min. tranny temp below which you should not drive?

Just trying to increase my knowledge about this beast that I bought and make sure I take good care of it.

Thanks for your help

The Pakman

Safety 1st....Good Times Follow

 

I try to keep my truck under 210 degrees. I never have a problem with that on the road, but I usually dont have to take off up big hills loaded either. The only time it usually gets to hot is when i am driving around in the field slow loaded. 4 low usually helps keep them down a lot when im in the field though. The temperature should be measured in the duty(hot) line to get a true reading(where mine is). There is no minimum temperature you need to go by with the auto. The cooler, the better for the most part. Once mine warms up just a little though, it seems to pull better through the gears(first couple miles of driving will take care of this). Pulling 8k lbs up a 7% grade; just try and stay under 210* or so. If you are hitting the hill with the converter already locked, then you wont heat your tranny up any at all unless it
un-locks, but if you are taking off on it, you will need to watch it a little harder. Any time the converter is locked, the tranny shouldnt heat up any; even when pulling. Not sure what effect the exhaust brake would have but here is what you need to know:

converter unlocked(loaded) = Tranny making heat very fast
converter locked(loaded) = Tranny not making any heat, and staying cool

Mine cools off really quick once the converter locks. Good luck and if you have anymore questions, let us know Hope this helps a little.

Eric

 

this is a usefull thread for me. How do you know when the converter is locked/unlocked?
My 04.5 has the tow/haul mode. I tow about 5k and on the interstate I tow in reg OD as the t/h puts the rpm way too high. I will put it in tow haul on big long pulls. My tranny temp gauge shows about 180 while towing. Is this a bad practice? thank. Never really understood slush boxes!

 

You want a minimum of 150 degrees in the transmission when working it hard. A little less won't hurt anything, but like an engine, they work best once warmed up. Fortunately it doesn't take long for a transmission to warm up. The max temp. is kind of a trick question. If you run well over 200 degrees, within reason, you won't hurt anything except the fluid itself. Once over aprox. 175 degrees, the life of the fluid is shortened. The hotter it gets, the shorter its lifespan. So if you ever really overheat it, get the tranny flushed ASAP. If you spend a lot of time in the 200-220 range, change your fluid fairly often. If you are down around 170-180, its not bad at all.

Your transmission creates the most heat while the torque converter is slipping. To reduce the heat, make sure the torque converter is locked. Thats why many on here who tow hook up a "mystery switch", which just manually locks the torque converter in 3rd and 4th gears. When on hills, taking it out of OD will help keep the TC locked while in 3rd. If you hook up a switch, it will help even more, since there are several times when the computer will unlock the torque converter- such as when the brake is pushed, or when you let off the throttle slightly. Every time it unlocks, and you get back in the throttle with it unlocked, it builds heat.

You can usually feel the converter lock up. It feels like the transmission upshifted a gear, and when you push on the throttle, the engine won't rev up without making the truck move faster. Kind of hard to explain, but think of a manual transmission with a slipping clutch. You can rev the engine some without going any faster, because the clutch is slipping. When the converter is locked, there is no slippage.

Jim

 

Thanks for the great information. So your answers generate some follow up questions:

1. The owners manual calls for replacing transmission fluid every 15k miles (I am going by memory). Assuming that I spend the summer towing through the mountains out west, I am sure I will run above 200 for maybe 30 minutes to an hour at a time. How often should I change the tranny fluid?

2. I make sure I am in Tow/Haul mode whenever I am on roads that are liable to have grades. Does the Tow/Haul mode lock the converter?

3. Is it better to leave the tow/haul mode on all the time when towing?

4. Who sells a good mystery switch and what does it cost installed?

 

Thanks Eric. Great info; but I can't really use 4L on the Hiways! So I have to make sure I stay in locked mode and watch the temps.

 

NHDiesel and cumminsdriver635 have given some good info. One thing that I will add is that the Tow/Haul button on the 2004.5 performs like the OD Lockout button on earlier models. It locks out 4th gear overdrive.

In 2005, the Tow/Haul button will not lock out overdrive, however it changes the shift points and does allow for some better downhill engine braking. The computer and the control of your throttle foot decides the gear selection when left in Drive. My Dad has a 2005 and towed their 5er (9000lbs) from VA to CA up to WA and back home with no complaints. Dad said it took a little getting used to as far as throttle control, but he was really impressed with its performance,, especially in the mountains.

I have read that the 2006 Tow/Haul button will perform both functions. One push on the button will put it in T/H mode without locking out 4th gear and pushing the button twice (double-tap) will lockout overdrive.

I have a mildly modded auto in my 99 and I also just recently installed a "Mystery Switch" for locking up the converter at will. I'm not really sure I would suggest doing this on a truck with the newer 48RE in it or one that is still under warranty as I'm sure a dealer would consider it a big NO-NO. Not to mention that when you lock the converter with the switch,,,, it's like driving a manual. If you forget to turn the switch back off before coming to a stop,,, it would be like stopping a manual in high gear with out pushing the clutch in. There are some wiring diagrams that use relays which are wired in with the brakes to keep this from happening, however I chose the easiest method as I don't intend on using it very often. One main reason for mine was for use when running the truck on the dyno,,, it keeps it from unlocking or trying downshift.

 

Okay answer to an earlier thread by Cumminsdriver635 and NHdiesel lead me to post this thread.

When towing anything heavy in the mountains Cumminsdriver635 and NHdiesel recommended that you should keep the tranny TC locked to reduce heat build up.

What is the best method of making sure TC is locked:

1. Downshift?
2. Go into Tow/Haul mode?
3. Go into 4HI on dry pavement?
4. Install a mystery switch?

I am sure as a rookie I am missing some other tricks that you guys have learned through experience.

As a rookie it almost seems to me like you are putting more stress on the tranny by keeping something in locked mode when the design engineers designed for it to go in and out of locked mode?

I guess another question is when you are in slow moving city traffic should you also keep the TC locked and if so how?


I am really enjoying the huge amount of knowledge on this board.

Thanks for sharing your knowledge.

 

#2 answer. On your 2005,,, it locks the converter when the computer tells it to do so.
#3 answer. I would say yes. Dad said that's what he did and when you are towing on level ground,,,, your final gear ratio will still be the same,,,, and the shift points when taking off from a stop will be better for the amount of weight you are pulling.
#4 answer I really don't think anyone sells a kit and as I stated earlier,,,,,, I wouldn't suggest doing this on your 2005 truck.

Just my $.02

 

What do you drive, or is your question hypothetical?

My transmission is always locked above the speed I select on my Commander, and stays locked during shifts up and down. Works great. OEM won't do that. A lock switch works for a lot of drivers but might be too much stress for OEM.

 

Sorry I should have stated what I drive:
2005 5.9L CTD HD 4X4 Atlantic Blue with the 4SPD auto tranny, Pacbrake EB, BD Cooldown Timer, Prodigy Brake Controller, Banks Pillar Guages, ARE Tonneau Hard Cover, Stainless Steel Nerf Bars, Mud Flaps, Bug Shield, Sirius Satellite Radio

 

I have installed the mystery switch myself, but you have to be watch how and when you use it, or tranny won't last. I am thinking of taking if off because I don't want someone to jump in my truck and destroy my tranny.

 

This will help with keeping it locked at certain speeds. Once you are slow enough that it would unlock in OD, drop to 3rd and it will stay locked longer.

What year truck do you have? Earlier (like mine) don't have a tow mode, just an OD switch to take it out of OD. I haven't checked out the newer Dodge trucks, but some vehicles with an actual TOW/Haul switch defeats the purpose, since the switch UNLOCKS the TC, so it isn't stressed while towing. Thats fine for the converter, but heats up the transmission substantially.

This will do nothing. 4x4 has nothing to do with how the transmission shifts, and will just stress the drivetrain parts- t-case, driveshafts, u-joints, front axle shafts and joints, etc. NOT a good idea!

I was advised that the mystery switch should be used with caution when pulling with a stock transmission, since you can actually harm the transmission by putting too much torque through the stock converter. I was going to use one, but I don't tow often, and just wanted it to help increase transmission life by limiting the number of times the TC locks and unlocks.

It all goes back to another thread that is running...if you want to tow, either get a built transmission $4000+) or a 5 or 6 speed. Stock Dodge transmissions are a serious weak link. I'm still waiting for mine to die. Hopefully it is still working when i put the 5-speed in, so I can sell it!

Jim

 

pakman,
I merged these two threads because you are basically dealing with the same subject.
If you have not towed with your set-up yet, you may be suprised to find that your 2005 48RE will do a good job of performing best by letting work as designed. As I stated earlier, my Dad was very impressed with the performance of his. You are already a step ahead of the game by having the gauges. They will give you a good idea of where your "Normal" zones are. Not all trucks are the same so therefore what may be normal for mine may not be normal for another truck like mine with just a slightly different torque converter,,, valve body,,,, line pressures,,,, and engine HP & TQ.
I think the 2006 48RE is better than the 2005 48RE because it enables you to have an overdrive lockout, however I think the 2005 48RE is far better than the stock 47REs are.

 

Man I am drowning in information!!!! There is a lot of knowledge on this board!!!
Rattlinram: Yes I towed with my CTD last summer, but I am going to do a lot more serious towing this summer, Utah, Colorado, Wyoming, Canadian Rockies etc. So I am trying to learn all I can so I can pamper the beast and make my investment last. Heck I paid twice as much as my first house and as much as my second house (30 years ago) for this baby!

Sounds like the best thing to do is:

1. stay in Tow/Haul
2. watch the Tranny Temp like a hawk
3. downshift before any serious grades
4. Change transmission fluid every 7500 miles or sooner if I get upto 220 on the tranny temp.

Am I a good student?