Allison is HOT. At what point am I "Overheated"

[Hunnington]

I know I am beating a dead horse, and I know it is a well documented problem but I did not think I had a problem (so I did not pay a lot of attention), but it looks like I do. Pulled through the hills in Virginia and WV last week and paid close attention to the gauges. I know they say they are not !00 % but they must be a good indication. My transmission temp went to over 250 and the engine temp would go uo to 235. The gauges were not in the "RED" but the tranny was close. At what point am I overheated? What will the truck do when it reaches that point? Will the dealership do anything? The truck is an 04.5 3500 with 21K and no Mods. I am pulling a 9K fifth wheel. It is my first diesel and I guess I expected a little more for 40K, I was slowed to 40 mph in 3rd on one grade, pulling less than 9K.

[More Power]

If the transmission reaches a critical temperature, the truck will go into "limp mode" (likewise with engine temp).

You should be running in Tow/Haul mode whenever temps exceed 210-220. This will help to reduce trans temps due to the torque converter locking in 2nd-5th gears.

Can you hear the fan-clutch engage? It should be while pulling grades like you mentioned.

Jim

[Mark Rinker]

What was the ambient temp? Winds? Your fifth wheel probably catches ALOT of wind in addition to its weight. 9K certainly isn't much, but the profile of your load is. For what its worth...

RINK'S RULES FOR TOWING HEAVY WITH THE DMAX/ALLISION:

1) Run tow/haul 100% of the time. Also - no manual shifting (automatics), or running your gear selector in a lower gear. Let the Allision TCM perform its function - its does well towing heavy in tow/haul mode. If it is 'busy' downshifting and upshifting frequently, your expectation of desired ground speed for your load/wind may be too high.

2) Establish a target cruising RPM of 1900rpms - accepting whatever speed that generates, depending on grade, wind, etc.

3) Listen for the fan clutch. You might have one that is not coming on early enough. That drone is a good drone. I have listened to it continuously on my LLY on level ground bucking hot headwinds.

4) Check for any obstructions to airflow over tranny cooler, radiator, etc. including dead bugs or restrictive bug screens intended to keep bugs out!

Your numbers are higher than I saw pulling 12K in the mountains. I did see similar numbers bucking a headwind in 90+ degree temps. My truck used oil on that trip, too. Its tough on them.

[Kennedy]

For the transmission, there is a cooler upgrade that will help. Were the trans temps hot going up under load, or coming down under coast?

[JD_Diesel]

Where can I find this trans cooler up grade? JD

[Hunnington]

They were hot going up the hills

[JohnC]

I found this chart many years back

http://members.aol.com/gmc65td/atflife.jpg

As you can see, things go down hill rapidly after you hit 240*

[Ranch55]

This is the upgrade cooler I installed on my '02 and '05 D/Max / Allison, and also on my '91 7.4L, 4L80E trans. This is a high flow cooler, regardless of what you might find written about it. It connected up OEM style without cutting / splicing any trans oil lines. It is manufactured by the same manufacturer of the OEM / stock cooler. For the 2005 application, I had to go to the dealer and purchase the cooler fittings for an 2002 OEM cooler because they changed from 1/2"NPT on the 2002 cooler to metric on the 2005 OEM cooler. You can also find this cooler manufactured / sold by B&M.
http://www.outdoorsunlimited.net/~texsas/

[Kennedy]

Where can I find this trans cooler up grade? JD

A company in Socal makes them. I can get you one and plan to offer them, but am waiting to see the 06 style retrofit before I decide which to stock.

[REDTRUCK05]

What was the ambient temp? Winds? Your fifth wheel probably catches ALOT of wind in addition to its weight. 9K certainly isn't much, but the profile of your load is. For what its worth...

RINK'S RULES FOR TOWING HEAVY WITH THE DMAX/ALLISION:

1) Run tow/haul 100% of the time. Also - no manual shifting (automatics), or running your gear selector in a lower gear. Let the Allision TCM perform its function - its does well towing heavy in tow/haul mode. If it is 'busy' downshifting and upshifting frequently, your expectation of desired ground speed for your load/wind may be too high.

2) Establish a target cruising RPM of 1900rpms - accepting whatever speed that generates, depending on grade, wind, etc.

3) Listen for the fan clutch. You might have one that is not coming on early enough. That drone is a good drone. I have listened to it continuously on my LLY on level ground bucking hot headwinds.

4) Check for any obstructions to airflow over tranny cooler, radiator, etc. including dead bugs or restrictive bug screens intended to keep bugs out!

Your numbers are higher than I saw pulling 12K in the mountains. I did see similar numbers bucking a headwind in 90+ degree temps. My truck used oil on that trip, too. Its tough on them.
On an 05 2500 HD 6.6 that is about 60? Based on the only other diesel I have owned, its not enough. Speed limit on interstate is 70MPH and if you dont do 70 you get run over. Never had a Problem with "the other" and I put about 50,000 on it. Paid alot more for this truck I expect the same if not more.

[Chris_S]

I am a bit worried when I do start towing after looking at my tranny temp the past few days. With nothing hooked up, or in the bed, my 07 classic tranny temp. is around 200, the outside temp was 102. My speeds were only about 50 mph, and it does not cool down when it is idling and in park. Seems like it is already running a bit hot unloaded, let alone when I go to tow my 5th wheel (12,000 lbs) through the desert next month. The truck has less than 3k on it.

[Mark Rinker]

I would say your temps are normal for unloaded driving. Don't worry - wait until you are loaded and see how it performs.

As for previous post - 70mph expectations while towing tall, wind resistant loads isn't realistic, IMO.

[socaltoolguy]

I have pulled our fiver with about 14k over the Rockies a couple of times and last year we came over I40 through Needles and it was 116 outside. There is a long grade so we just turned off the AC and let the truck do it's job. The engine and trans didn't get hot at all. I would have your truck checked out. It sounds like it is running too hot. We have towed all over the country and never had a cooling problem. I watch my gauges closely also.
Ray

[More Power]

Use Tow/Haul whenever you think the trans temps are above where you'd like to see them. With T/H, the torque converter is locked in gears 2-5. In town stop-n-go driving and not using T/H, the temps will climb cuz the torque converter is unlocked. Out on the open highway (or running in 2nd or higher gear), the TC should be locked. This usually allows temps to decrease. :)

Jim