04 48re getting hot, shifting differently

[Smoke Eater]

Pretty much what the title says. I rebuilt the trans a few months ago, Goerend valve body, Precision billet RV torque converter, gpz frictions. After fixing the wires in the 8 wire plug, all is well, shifts great.
With summer here and Temps in the 90s, I've noticed the truck runs a little hotter than it used to, 205°-210°. Last summer it stayed around 200°.
I did install a Goerend deep pan and a trans temp gauge in the pan. Highway driving unloaded sees 150° trans temps, coolant is at 200°. Stop and go in town unloaded trans gets up to 195° and the coolant temps are 210°. Once the trans gets to 190° the shifts are harder, and it wants to go to lock up and overdrive a bit sooner than it would normally. Biggest problem with this is compressor surge when it drops 500 rpms so quickly. Compressor surge has always been a minor problem, I adjust my driving to compensate, but the erratic shifting is a problem. Could the governor pressure transducer, governor pressure solenoid, or the overdrive and lockup solenoid be the problem? I'm leaning towards the overdrive and lockup solenoid being bad, wanting input on that.
I'll be changing the thermostat out with another 190°, and am planning on installing a Dynamic Transmission cooler thermostat delete kit in the next week.

 

[SSage]

My coolant temp runs 198 most of the time solo or loaded, original T stat. Thats what the Edge monitor says. In traffic it hits 212 sometimes pulling the 5th wheel slow, especially in the hills. But at 96 degrees outside it ran 175 to 196 on the trans temp through Atlanta pulling a 5th wheel slowing down multiple times.

I've always gotten that 500 RPM drop with the aftermarket billet TC's. Both of my trucks with 4 speed autos will bark a bit when pulling, especially with the big turbo on the 95. I've been having issues with the shift selector cable working itself loose on my 03, it bit me twice this year and made the trans shift like it was possessed. I thought something had broken one day, the odd shifting suddenly got worse and I was getting neutral with out touching anything while pulling hills. Shortened the shift cable up again and so far its staying tight. But that cable will make the trans shift weird when it gets frayed or just stretches. The selector worked okay inside, so I didn't suspect it at first. TV cable has given me issues too, I've had to replace one that would not stay adjusted on my 95.

 

[cerberusiam]

At 190 you should not be seeing ANY change in shifting, that temp is just a normal range for a 48RE. Usually only see a different shifting algorithm when the temps get over 230 degrees. The 150 degrees at empty cruising is not normal either, that should be a lot closer to the coolant temp than not. That along with shifting change at 190 makes me think you are not reading the temp in the right place or the probe that is reading it is whacked.

Would help if you would detail where and how you are getting those readings and any mods to the trans cooling system.

 

[BigPapa]

For accurate transmission temps, sensor should be in the line before the cooler.

 

[Smoke Eater]

Only mod to the transmission cooling system is the heat exchanger/ torque converter cooler has been bypassed. I thought I had listed this, but obviously didn't. That would have been helpful. I did this on the advice of a trusted transmission shop, but after reading up on it, I'm not sure that was such a good idea, I'm planning to return that to stock. Maybe that's fine for a pulling truck, but not a DD.
The readings are coming from the pan, Goerend has their sensor location at the back of the pan. I've got an autometer factory match gauge.
I agree that at 190 I shouldn't be seeing any difference in shifting, as that's its normal operating temperature. From what I've been reading, it's likely that the temperature coming from the torque converter is easily reaching 240. Considering the truck is unloaded, even with an air temperature of 95 this seems excessive. If the shifting algorithm starts to change above 230, then that makes sense.
I'd like to find a fitting for installing the sensor in the line going to the cooler, not sure as I want to attach the sensor to the outside of the line. I'll be on vacation next week, that will give me the time to get these things done.
One takeaway from all of this, running cooler Isn't necessarily better, keeping the transmission at it's optimal operating temperature without overheating is where it's at.
Thanks guys!

 

[Ozymandias]

The water/oil heat exchanger takes the main load on a Gen3. Bypassing it would mean you have to use a 3 times bigger air/oil radiator in the front.
Do you have that?

 

[Smoke Eater]

Nope, that's one thing the trans shop failed to mention. It runs cooler, until it doesn't. I should have known better.

 

[SSage]

I would put it back to stock. You also want it to warm up ATF in the winter, but that bypass cuts a lot of cooling. If I'm moving above say 50 mph my 48RE always stays below 200. When it gets really hot, the engine fan kicks in and it goes to a fast idle if your in park. I was backing a 5th wheel in up a hill and got mine hot once, I put it in park and it idled up as I got out with the fan roaring. Both my auto trucks use deep pans and they both read about the same trans temperatures.

 

[cerberusiam]

The temp readings used by the TCM come from the transducer on the VB, only place temp is read on a 48RE. However, the transducer are notorious for reading wrong, drifting measurements, and just generally screwing up trans operation. If you have not replaced it lately, with a Rostra product for best results, it could be the root issue. VB harness leaking in the case plug is another area that will cause erroneous readings from the transducer which can and will make a lot of weird things happen.

 

[Smoke Eater]

The harness appears good. I'll replace the transducer, it's simple enough. Pretty sure I've got a new one in the parts cabinet.
Thanks for the help.
I'll post an update next week when I get to fix my mistakes.

 

[Ozymandias]

Get the Rostra HD one!

 

[AdamRRT]

Got a part number on that Rostra item? 50-1171?

 

[Smoke Eater]

I've got one with a part number of 12415C, it's a transtar number, but also seems as though it's made by Rostra. It's the HD model.

 

[Ozymandias]

Got a part number on that Rostra item? 50-1171?

Yes that's the good one.

 

[Ozymandias]

I've got one with a part number of 12415C, it's a transtar number, but also seems as though it's made by Rostra. It's the HD model.

If it has the white plastic cover then it is the HD, if the cover is black then it's the standard one.

 

[Yo Hoot]

On a side note check and make sure your fan clutch is operating. We recently moved to Texas from PA. Drove down and back 1400 miles once and one last time for the final move. While down here all of a sudden I was getting hot at traffic lights... A/C got warm until I was over 30mph and the trans was shifting funny. I was thinking thermostat but when I got home I took a peek under and saw the cable from the fan clutch was ripped off. I'm starting a separate thread on that debacle
here https://www.turbodieselregister.com/threads/2004-fan-clutch-debacle.271643/