hey there, I have 07 5.9 mega cab 3500 automatic trans

I have a pretty much stock truck, only add ons are a 4 inch exhaust, and a cold air intake. oh, and i put my 34 inch tires back on this weekend.

I have an edge insight monitor. ( no tuner, just monitor)

last summer i pulled an 11000 lbs 5th wheel up very steep highways. tranny temp never went above 185. only time i saw it climb was when i was backing it into the site. ( lots of forward reverse) maybe hit 205-210
that was with the 34 inch tires.

today i went into the bush. was driving on gravel road, which was slightly muddy. noticed i was spinning a bit so put it into 4 wheel drive. the gravel rd was fairly steep, but nothing that made me say wow. during the climb i noticed tranny temp was about 180, then 185, 190, 200, 210 220, ( alarm went off then it hit 224 at that time the road started to level out, but temp never dropped below 200.. I let it idle in neutral, and it did slowly start to drop.

I usauly drive on the free way, and its usualy around 155-157. and city, maybe 165

now I have driven the truck on the highway in the winter in 4x4 and tranny temp never went up. so keep in mind i was in 4x4 this time, but wasnt going over 50km/per hour

checked fluid... nice clean and at a safe level.. fluid was changed last august, about 15k ago,

thanks, sorry for the long post

any ideas?

 

I wondered if your fluid is full first off, and if full, 50kph works out to about 30 mph and that is where my transmission will start to warm also. The problem is the torque converter is producing much more heat AND not getting the airflow through the cooler to keep up so the trans temp will raise. Mine has never got above 200* but I pull a 8.7k bumper pull toy hauler which also doesn't push as much wind as your 5er. Two ideas come to mind: getting a bigger trans cooler, which many 5ers get and a deeper aluminum pan to hold two more quarts of fluid. The temperatures you're seeing pulling that load up a good grade at that speed seem logical but I would think making those changes should solve your problem IMO.

 

I thought what I had was fine. When I pull the 5er I don't go above 185 but empty I hit 224!!! That's insane. . I took it for a test drive today. 120kms in the free way at 105km per hour (60miles per hour) never went above 155 degrees. Then I took it up a windy road in 4x4 very steep and did t go over 190. Then came down the hill in second and the temp dropped to 165. I'm wondering if it was just that the road was muddy when my tranny temp shot up.

 

One other thing that's common is a partially plugged trans cooler. It's real easy to over look checking for bugs and various road crud blocking off quite a bit of the cooler. Also since high trans temps seems to be what kills trannies most, you might be wise just to look for a more heavy duty cooler. I've never priced one but it can't come close to the cost of a trans rebuild.