2007 5.9 48re

[JohnMcKeehan]

My other post about injectors had starting morphing into a transmission thread. Thanks Cerb. for the help. Here's the new info. Truck has a smarty touch, just using it for gauges right now. I've had the truck 7 months or so, has 249,000 miles on it. Headed out about 3 months ago towards St. Louis pulling a 35' gooseneck with my 85 crew cab on it that i was selling. Got into the hills south of St. Louis and truck started acting funny, RPM's up, and then truck kicked completely out of overdrive. pulled over, checked fluid, and connections to transmission, everything was good. after it cooled for about 15 minutes, restarted truck, and was easy on it rest of the trip. started looking at options for a trans temp gauge after that. Got the smarty, pulled the pan on the transmission, fluid was still red, no burnt smell, decided to go ahead and install a new solenoid pack in it while i had it apart. also added a deep pan. For the last 2 months, I've had increased temps, up to 210 degree's on freeway, unloaded at 70mph. I removed the check ball in the line, no change. With Cerbs. advice i cleaned the thermostat in the cooler. initial thoughts were this was going to do it. around town, big difference. temps stayed about 155-160. on freeway for 1 hour yesterday, cruise set on 70, mostly flat with rolling hills, temp climbed to 195. Seems that i lost lockup too once the heat started to build. It is my understanding that Lockup can be stopped by the computer when temps rise to help protect the transmission. Does anyone know what that temp threshold is. I have relegated myself to the fact that a rebuild is in the near future, just trying to make sense of the temp fluctuations.

 

[cerberusiam]

Where are you reading trans temp? The 195 at cruising is in normal range with the TC locked, if you are towing and the TC is not locked you would see higher temps like 220-240 or so. Running empty not so much but would probably top 200. The default for over temp is drop OD and lock the TC. TC locked is the coolest mode of the trans so it will default to that. TCM starts showing lights and aggressive shifting at 240, at 260 it will go into full save mode.

The 195 is a general number for temps in our normal range of 60-90 degrees ambient. Based on what mine does at 30-40 degrees towing a moderate weight at that speed probably should have been in the 170-180 range, with a good analog gauge. If you are reading trans temp from the data bus even the 195 is not out of line in cool temps as that has been smoothed and adjusted by the TCM reading from the transducer in the pan.

If you feel lockup is getting soft and almost disappearing when the transmission warms the TC is the likely source of that problem. Lockup should be firm and noticeable at all temps but it definitely is a lot softer in a stock TC and will get softer with age.

 

[JohnMcKeehan]

Thanks Cerberusiam. I'm reading from the OB2 port through the smarty touch. so i'm assuming its reading at the valve body. The info about the temps makes me feel better. Lockup is soft at any temp, I had a built transmission in my 06 and was extremely happy with it. This is my first stock 48re, so i don't really have anything but a built transmission to compare it to. I'll keep an eye on it over the next couple of weeks and keep some notes.

 

[cerberusiam]

Yeah, a built transmission spoils the experience and enforces how sloppy the stock stuff is.