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Warpspeed
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20 Posts
Discussion Starter #1
My '04 SLT with the 5.7 (144k) just started downshifting harshly during what I think is the 4-3 shift. It occurs when slowing down at just under 40 mph. In tow/haul mode it doesn't do it.
I have all of the service records, and according to them the trans was just serviced about 20k ago. I should note that I just recently bought a superchips 3845 programmer and installed the 91 octane program, but I didn't make any changes to the transmission settings because I also have a Sonnax pressure booster installed, which was in place before I got the programmer.
 

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Start off with loading back the stock tune from the 3845, and see if that helps. If not, then drain & replace the trans fluid, and install Mopar (Not aftermarket crap) filters (2). And go from there.
 

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Warpspeed
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20 Posts
Discussion Starter #3
Tonight I put the PCM back to stock and left the Sonnax pressure booster in place. Up & downshifting was flawless. Could definitely feel the power difference (loss) with the superchips taken offline. So next I'll put the 91 octane program back in and remove the pressure booster. If it works well then I'll try the superchips shift settings. Even though I had not selected any of the transmission tuning options, it's obvious there are changes made to the shifting with the superchips even if they're not asked for. I'm just glad I'm not replacing a solenoid pack or rebuilding the trans. Stay tuned!
 

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Warpspeed
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20 Posts
Discussion Starter #4
Update: Removed the Sonnax pressure booster yesterday and put the 91 octane program back in with Superchips shift torque settings and stock shift points. The harsh 4-3/3-4 shifts came back immediately. A local trans guy I talked to said the harsh shifts wouldn't hurt it but I still don't like it. It's now back to stock with the Sonnax pressure booster and all is well. I can feel a significant performance improvement with the 91 octane tune in it so it's pretty disappointing that I would have to live with the funky shifts in order to enjoy it.. So, the Superchips is going back and I'm going to look into other options for tuning.
 
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