Hey folks. First post here trying to solve a mystery. The tranny in my '06 3500 gets hot. The first time I was towing a 8000 lb. trailer up hill at slow speed. The dash warning light came on, luckily I was only a short distance from home. Fluid level fine, didn't appear roasted, dealer checked and no codes in computer. I installed a temp gauge and a larger pan, but still it is not uncommon for the tranny to get up to 210-220 when driving uphill at slow speed empty. Around town on level ground the temps are 190-200. Towing the 6000 lbs in an effort to reproduce my first overheat, the tranny temp got up to 250. This cannot be normal. I have only seen a few other similar threads with no real cause/solution. Questions: Is this common? At what temp does the dash warning light come on? What could be the probable cause? What is the normal operating temp for the 48 in a one ton? Thanks in advance for any input.

 

I got a 3/4 ton and hot rodding it with the smarty I can't get it above 180 with a stock pan. The ATF starts to breaks down at 230, Towed 8000 pounds with the smarty on 60HP and could not get above 170. Does you truck have the Tow package with the Aux Trans Cooler?

 

I would make sure that it has a Aux trans cooler. If it does & you're getting it that hot, sound like the torque converter is bad.

 

Things start getting ugly at 210. At 230 ATF starts to break down. At 250 Carbon Forms and self distruction starts. Any time over 260 the "Tow Haul" light will come on and it will disable 4th gear and engage the converter clutch once the trans recovers to 230 things will return to Normal. So....as for your light VZDUDE is knowledgeable with that stuff.

 

ATF+4 is a group 3 synthetic fluid, it is rated to 320 degrees for short periods. Anything under 250 is well within its operating range. The new fluids are a far cry from the old Dexron.

It doesn't matter what you do stock, if you tow heavy weights at slow speeds the fluid will get hot. You have to get the TC into lockup to keep the temps down. Lockout OD and run in drive so the TC locks. Manually downshift to 2nd so the TC will lockup if the speeds allow it.

If one wants to spend some money, a good TC and a lockup controller will help considerably. Much more effective than coolers and deep pans.

 

I tow in the mountains and around sharp corners which means up/down and around. Lots of accelerate/decelerate. Which means many times TC not locked and temps can go up fast!! It is not uncommon for me to see 230-250 in those situations for short periods. I am using Amsoil ATF, but still, like ATF+4, rated to 320* as no 6 oh no correctly stated. FWIW... I employ Goerend's triple disc TC, mag-hytec double deep pan, aux trans cooler and TC lockup switch available in all gears, 1-4.

 

I agree,my tranny temps towing rise to 200-225 for short periods (outside temps 85-90 degrees)according to my BD X-montier.coobie

 

...and back to the point at hand. Your trans temp light will come on at 280, and will not shut off until it sees less than 230. Couple things here. How heavy is the boat and how low of speed are you talking here? Are you going so slow you can't achieve 3rd lock up? If your talking really slow remember that if you shift to MANUAL 2ND you will be able to achieve torque converter lock up.

 

I would say there is really nothing normal with a trans running at 250*. You need to verify several things. 1st - there should be 2 coolers. One on the engine block at the rear of the driver's side of engine near the bell housing and one behind the intercooler. #2 make sure that there is no debris in the fins of the intercooler, a/c condensor,trans cooler or radiator. #3 this will take some doing, but you will need to verify the temps. Is it actually running that hot? #4 If it is running that hot, you'll need to check several more things! - #1 how much fluid is the trans flowing thru the cooler? #2 What is the fluid temp coming out of the water to oil cooler? #3 What is the temp coming out of the air to oil cooler? #4 Are there any restrictions? There is an anti-drainback valve in the line from the water to oil cooler to the air to oil cooler. I TAKE THOSE OUT! ( some I have drilled the checkball out, others removed completely- mostly second gens though) I actually just replaced the lines on mine, and left it in this time! ( why? I have no idea! I was in a hurry I guess!) They have been accused for years of failing and causing a restricted fluid flow, in return - failed transmission due to overheated fluid.

Here's the info on the light BTW.


OPERATION
The PCM prevents engagement of the converter clutch and overdrive clutch, when fluid temperature is below approximately 10°C (50°F).

If fluid temperature exceeds 126°C (260°F), the PCM causes a 4-3 downshift and engage the converter clutch. Engagement is according to the third gear converter clutch engagement schedule.

The Tow/Haul lamp in the instrument panel illuminates when the shift back to third occurs. The transmission will not allow fourth gear operation until fluid temperature decreases to approximately 110°C (230°F).

 

Am I on the right track to say that in order to lock up the torque converter you have to be out of 4th gear on the 48re trans and once its locked it stays in that gear,lets say 3rd????I dont known too much about how the system works.I do tow a trailer that is 14000 lbs

 

The torque converter clutch is controlled by the Powertrain Control Module (PCM). The torque converter clutch engages in fourth gear, and in third gear under various conditions, such as when the O/D switch is OFF, when the vehicle is cruising on a level surface after the vehicle has warmed up. The torque converter clutch can also be engaged in the MANUAL SECOND gear position if high transmission temperatures are sensed by the PCM. The torque converter clutch will disengage momentarily when an increase in engine load is sensed by the PCM, such as when the vehicle begins to go uphill or the throttle pressure is increased. The torque converter clutch feature increases fuel economy and reduces the transmission fluid temperature.

 

Its quite normal in slow speed traffic and slow speed pulling. The TC never locks and it just drives the temps up. Most people don't know that if you manually shift the trans down to 2nd the TC will lock in all but the hardest pulls. Leave it in drive and the TC will almost never lock up under 45 mph with a load on a grade.

Everything you posted is good to check if you have heating problems at road speed, but, low speed towing on a grade it won't make a difference. The only way to keep the temps down is get the TC to lock and stay locked.

 

I drive thru heavy traffic everyday, not pulling a load everyday, but have done that too, and have never seen more than 205* on my guage. I'm pulling over if I see 250*! FWIW

 

.....and I did pull my 24 ft enclosed with my old 95 1500 (approx 8500lb) and would see around 300 degrees (gauge sender in the "hot" line) pulling the 16 mile 6% grade to get out of this hole I live in (factor in many days towing 110+ ambient). Serviced that trans about once a year and it never let me down. Truck got sold local and is still goin strong. I must note that we did overhaul it at about 35K.....just because we wanted to.

 

My 06 would do this last winter while pulling up steep grades with our 26ft enclosed sled trailer at slow speeds. I could really tell when the TC was slipping (normal) because the truck seemed to be sluggish and the trans temp would rise quickly. I just put the truck in 2nd and let the engine rev a little and the truck would pull a lot easier and the temps would drop back to the 140 range. Do not be afraid to try and find an optimal gear instead of the truck trying to find it for itself because a lot of the time it is wrong.
-Jeremy