MtnDodge

Ok, apparently I had this in the wrong forum (2007-up) as all I saw was the 2003 and up. Now it's in the right place! Still looking for answers though!!!
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Today I went down the mountain to buy hay. It was hot there- over 100F. I loaded up a stock trailer and started the drive back. (No, I didn't run the AC- just sucked it up and went!) Total weight- between 5-6,000. Not a lot that's for sure. The grade coming home runs between 12-17%. (that's not a typo) I had it in Tow/Haul and was taking it easy. About 40 minutes into the drive, and only about 10 minutes into the mountain climb it suddenly felt like I might be losing power, maybe the tranny slipping some. Up until then it was strong and staying at around 1800-2000rpms. It revved back in when I pushed it some and I continued. About 10 minutes more in the climb I could tell the tranny was having some issues as every time it shifted it shifted HARD with a big thunk. I don't have a temp gauge on it yet but wondered if it was getting hot so I pulled over, sat for about 5 minutes, then turned it off and let 'er rest for about 20 minutes in the cooler mountain air. Made it the rest of the way (20min) up the mountain with no issues- but I kept it in second. During all of this the other gauges were all within normal, no warning lights anywhere. The only thing out of the ordinary was when I turned it back on I got a light that said "check engine gauges"- which I'd already done but as stated everything was normal. I checked for codes before restarting it and got nothing.

So...does that sound like the tranny was getting hot? or something else? Did I do the right thing or was there something better I should've done? This sucks cuz I was really thinking my truck was just a good running machine! Please don't tell me to get a stick- not an option. Oh- this is not the first time I've pulled this grade with a load but it's the first time that I've pulled it in the heat. Help?
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badme

You need some gauges in that thing. A shift kit would be good too. The first mod I did on my truck was the shift kit. If you are going to pull that kind of grade in that kind of heat and you are not going anywhere where the temperature gets below -10 or so, I would by-pass the radiator cooler and only run the external cooler. This will be a good start.

1stdodge

Sounds to me like you started to boil your transmission fluid. Once you boil it nothing works right.
I would change the fluid, as if you did over heat it, the fluid is probably ruined.
ATF 4 looks and smells burnt right out of the bottle, so looking at the tranny dipstick may not tell you much. I was always told the best way to cool down a transmission is to idle the vehicle. A big tranny cooler and frequent tranny fluid changes (when towing hot) should help.

no_6_oh_no

How fast were you going? Are you sure the TC was locked?

If you were not going very fast it may have just been unlocking and heating the fluid up. You may be much better off locking out OD and staying in drive if it slow speed driving.

You definitely need a gauge to monitor that trans temp, and a shift kit to help with the pressures.

dieselfumes57

ok... am i missing something......he's got a 40k truck and he cant pull a hill with a stock truck with 5 to 6k behind it without everybody saying he's running the tranny hot and he needs guages and a bigger tranny cooler....lol ....this truck should be able to do this no probs at all with nothing needed. if it wont then you need to go buy something that will.

TrkEnvy

Actually the best way to cool a non modded tranny is to put it in neutral and bring the revs up to 1800- 2000..

cujo

Ever towed up a 17% grade? I've towed 16% and the fluid starts getting really hot after a short time.There aren't a lot of 16-17% grades around but they're tranny killers when towing at 90 - 100 degree weather. I can yank my 9000# fifth wheel up 6-11% like nothing, but when the road gets that steep, it's really tough. You have to get a guage on and change that fluid

J BODY

Wow! a voice of reason! First of all the dollar amount of the truck really has nothing to do with the issue. I really don't think whether the truck was $1 or $80K gives any clue as to what needs to be addressed.

So we know the grade (dang steep!!), we know the load weight (very helpfull). So fill in the rest of the blanks. What year truck? 03 early build with a 47re?? Late build with 48re?? (we can "assume" 48 since you refered to "tow/haul", not OD lockout......but we all know what "assume" means). What rear ratio?? How fast were you going?? Running some show pony oversize tires??