I have a 2006 2500HD LBZ/Allison 6-spd. I have about 1000 miles on the truck and I made my first trip with the trailer over Thanksgiving. I am towing a 31' toy hauler that weighs approximately 10K lbs loaded. About halfway through the 300 mile trip, I hit some mild hills, nothing major. I noticed the tranny temp climbing and actually got the "Transmission Hot" warning on the DIC. I slowed down and tried to baby it along but then got the "Transmission Hot. Idle Engine" message. At this point the temp gauge was close to 300 degrees. The outside temp was about 80 degrees. I pulled over and idled the engine and contacted OnStar for the nearest dealer. After 20 minutes of idling, the temp was still around 240. I drove carefully to a dealer about 10 miles away. The tech said they thought it was a sensor malfunction and replaced some temp sensor in the tranny. BTW, the tranny fluid was still red and did not smell unusual.

Well, we continued the trip (after the 5 hour dealer visit). It was now nighttime and the outside temps were about 60 degrees. I still ran 220-230 the rest of the trip. To me, that seems very high. The next door neighbor was on the trip with us. He has a 2003 LB7/Alli and tows a slightly heavier trailer. On the exact same route, his tranny was running at about 170-180 and never approached 200.

On the return trip yesterday, the tranny ran about 180-200 the whole way, in 55-65 degree weather. This seems a little high, but I'm not sure.

So, do I still have an issue? Should I load the trailer back up and put it through a torture test on the local grade? I'm just concerned because the Allison is the last thing I ever thought would give me trouble on this truck. In addition, my 8.1L Suburban with the 4L85E, never had tranny heat issues pulling this same trailer.

Opinions? Advice?

Sounds to hot to me. I wonder if the converter is not locking up or slipping.


My dad's '02 DA with combinde of about 30k never gets much over 200deg.

180-200 is normal operating temperature, but your trans shouldn't be getting as hot as it is. Could be an internal problem to the trans or a cooler problem. A flow test through the cooler would be able to determine that.

I doubt the dealership fixed the problem, sounds like they just threw parts at it.

I would first road test with Tech 2 and check for converter slippage then I would do a flow test on the cooler. Cooler flow test should be done at highest operating temp. You can be fooled testing a cold cooler.
mike

Were you running it in 5th gear or 6th? Was it constantly hunting between 5th and 6th?

There is no tq transfer while in 6th gear and probably not a great idea to tow in that gear.

I had it in Manual mode, locked in 5th gear and Tow/Haul activated. I am going to reload the trailer and retest on the local grade. I will make a few hard runs up the grade with the A/C on and see what the temp does. If I am able to reproduce the issue, I will go by the dealer and get a tech to ride along with me.

kazuaki , for your own peace of mind and to protect yourself , get a wieght on a certified scale Before!! your dealer trip.

kazuaki , for your own peace of mind and to protect yourself , get a wieght on a certified scale Before!! your dealer trip.

You mean to ensure I am not overweight?

There is no tq transfer while in 6th gear and probably not a great idea to tow in that gear.

Can you elaborate on this Mike, if you're towing in tow/haul, it will shift into 6th around 65mph if the engine isn't under a lot of load. If you don't want it to use 6th then you would have to drop it to 5th in manual mode and then you wouldn't have the automatic grade and cruise grade braking available. I've gotten into some head wind running 75mph in tow/haul and when it could no longer maintain speed in 6th, it downshifted to 5th and stayed there for 20 miles until my direction changed and the engine load diminished.

As far as I can tell 6th gear allways has the converter clutch on. There is no tq multiplication ( converter unlock ) in 6th. I think 6th is a good cruising gear but don't think it would tow well.

I have never seen my tranny temps anything over 150. Even unloaded, it barely gets over 100.

I have never seen my tranny temps anything over 150. Even unloaded, it barely gets over 100.

Tomorrow I will be loading up my trailer and pulling up a local grade here 2-3 times back to back to see what temps I get. Unfortunately, the outside air temps have been dropping and it will only be in the mid 60's. I would prefer to try this in the heat of summer.

On a side note, after driving the truck VERY CONSERVATIVELY around town, with no load at all, my tranny temp was 165 degrees. Isn't that high for no load, light throttle driving in 55 degree weather? My neighbors LB7/Alli runs cooler than that when towing his 5th wheel.

So, I loaded up the trailer and headed off to the scales first. The total truck/trailer weight was 19,040 lbs. The truck was 7,320 lbs. of that, leaving the trailer at 11,720 lbs. Definitely more than I expected, but still within the trucks limits.

The CAT scale I went to was in Castaic, CA. This is conveniently at the base of the grapevine grade. For those not familiar, it is a grade going from about 1000 feet of elevation to over 4100 feet at Tejon Pass. It is not super steep, but it is quite long.

Unfortunately, the air temps were cool, 70 at the base and 60 at the top. I set the cruise control to 60 MPH and let the truck do the work. Peak tranny temp was about 200 degrees. I made a loop and reran the last few miles at a higher rate of speed and was able to get the tranny up to about 210, but that is it. I also had the A/C on, but with the low outside temps it may not have mattered much. Engine coolant temps stayed about 200 degrees. I also noticed that even on the downhill and flat sections, the temp stayed right around 190-200, never dropping below that.

So, do I still have a problem with my truck? Considering the weight of the trailer and the outside air temps, should I be running cooler? Many people claim they tow at 150 degrees, why can't my truck?

Getting the rig weighed and hanging out with the big boys :D

http://www.nuibe.com/truck/truckstop2.jpg

Hard to say. This is a touchy topic for several people. Personally, now this includes my truck and may not apply to others.

I bought it in southern Louisiana and towed about 8-10,000 through Louisiana, Mississippi, Alabama, Georgia, South Carolina, up through North Carolina in August. I never saw any temps go higher than say 125-130. This was with a/c, cruise control set at 78. I did this route twice. Then I drove to Syracuse NY from southwest Louisiana, about 1700 miles, in september. Obviously, the further north I went, the cooler it ran. However, fron Tennessee on up, all it was was mountains. Up and down. I climbed some pretty good grades through Virginia and Pennsylvania and I was not exactly easy on the truck. I was runnin with Hypertech set on level 3 and never once had an over heating or excessive EGT issue. I worked it quite hard at times. I burned a lot of fuel. I have been sittin in traffic in Houston in 100 plus degree temps and saw it hit 150 one time and as soon as the speed picked up, it went down.

I would say that your temps are a bit warm. I'm sure this will start another overheating thread and I do not mean to get this going again. I hope this helped.

Unit453, I really appreciate you input. It is input like yours that makes me wonder what's up. How can you and I be running 80 degrees apart from each other? My tranny runs hotter than yours even unloaded :eek: Is my coolant temp of 200 OK?

I towed a back hoe from Br La to grandisle and back and tran got between 150 and 200 and temp out side was in the 80 plus range but I keep it about 45-60 depending on speed limit. Pulling trailer about 70 plus got 16 plus mpg and overall with hoe got 9-10. My tran on normal day like today in 60's runs 150.

Coolant temp at 200 is ideal. Anything less and your motor is not operating at efficiency. I just put on my winter cover tonight. Its warm today but last week it was around 15 while driving home from work. 75 miles all interstate cruise set on 75. Temp has been runnin at 180 or so. I constantly look at it. I can totally tell when the coolant starts to circulate. It goes from 200 down to about 165 and on back up. My tranny temps run at or just under 100 depending on the angle that I look at it. Maybe its me. Maybe I'm a bit parranoid about overheating. However, 18 months and 35,000 miles, 30,000 of which was runnin through 100 degree heat with rediculous humidity in the deep south, and never once a problem. Some trucks run hotter than others. Some people grossly over load it. Some dont tow at all. I guess I should feel lucky that its runs a bit too cool for my tastes. Hopefully with this winter cover, it will stabilize at 200 for the duration of my 150 mile trip to and from work. I'm not trying to get you worried. My experiences may differ from a lot of guys here. I wouldnt be too worried about it. If you may happen to stop by a dealer, ask around to one of their diesel techs and see. I did so with a few questions and got some really good info on a few subjects. I was advised to change my fuel filter every other oil change. I know its pricey but if it helps with longevity and performance then thats what I've been doing. I hope this helped...

At full operating temperatures my trans usually runs right around 150 when I'm unloaded. Maybe the 06s run warmer than earlier trucks. I know MikeL said the cooler was different for the 06 6spd Alli.

Getting the rig weighed and hanging out with the big boys :D

http://www.nuibe.com/truck/truckstop2.jpg

Which one is yours? ):h At this point I would not be worried about your temps. I would have liked to seen how much of your pulling the grade was with the TTC unlocked. It would be very interesting and informative to test a quick coupling converter ( much more efficient ) in your ri with no other changes.
mike.

I'd like to get behind the wheel of that Pete on the right.

It would be very interesting and informative to test a quick coupling converter ( much more efficient ) in your ri with no other changes.
mike.


Seeing as how you are both in CA, that might be a definite possibility.....as long as someone brings the :beerchug:

I'd like to get behind the wheel of that Pete on the right.

I do a lot of interstate driving and used to pass and repass all the big rigs in rolling hills. Lately though (last couple of years) I've noticed that some big rigs are keeping their speed on the uphills and even overtaking and passing me!:eek: Those rigs? The Volvos! You can have the Pete, I'll take the white Volvo on the left!:)

Nothing passes me on hills.

Nothing passes me on hills.

I like to "set and forget" my cruise control at 5 mph over posted. It makes it a lot easier to pull off my shoes and socks and wiggle my toes in the wool on the sheep's back!;)

I like to "set and forget" my cruise control at 5 mph over posted. It makes it a lot easier to pull off my shoes and socks and wiggle my toes in the wool on the sheep's back!;)

I thought I was the only one that does that kinda stuff.):h :D

I thought I was the only one that does that kinda stuff.):h :D

Naaaaaaaaa! When I enrolled in "Animal Husbantry" in college I was thrown out the first day of class when I lead in my wooly fiance'! :eek: WTF? Was that Baaaaaaaa-d?:D

Waaaaaaaaaayyyyyyyy - too much information!!!):h