MWM said:
Hey guys,
I just installed the 93 octane tune from the SCT on my 2005 QC. Nice power but under WOT when it's going from 2nd to 3rd it revs well past 6k and then either hits the rev limiter or something because it just powers down like it's bogging down. Never shifts through.
Runs great under normal driving but it does this every time wide open. I destroyed the auto tranny on my first truck but this one has been great. I'm at 35k. I don't want to rip this trans up, but do want the extra power. What's going on?
Anyone have any ideas? Do I need to call Marty and download a new program? Thanks in advance for any suggestions and help.
I've got a 2005 QC and have been dealing with exactly the same problem. I and my local transmission guy talked some with Joe at Westminster. I also have a great Dodge dealership that I've worked with on it. Bottom line is there aren't many if any folks out there experienced at dealing with the 48RE modified for SRT10 installation. What you've described is not tune related or fixable with tuning.
I didn't first have the problem until a couple of months after installing my TransGo shift kit. I'd been running a DC Performance Stage II tune for a year plus previously and never had a problem. For a couple of months after installation of the kit I posted on VTCOA that the TRansGo shift kit made nearly as much improvement pertinent to driveability as I'd gotten going from the stock PCM to the Stage II. When the shift problem at WOT first showed up it didn't happen all the time but was 70% of the WOT 1-2 shifts and 60% of the WOT 2-3 shifts. It behaved as though it was hitting teh rev limiter then having difficulty shifting. Through time the problem frequency increased. Dan Cragin's first reaction was that it was not tune related. He had the patience to work with me anyway and my PCM went back and forth to California 5 times adjusting shift points and the rev limiter, to no avail. Bottom line was he was correct as to what at that point was not the problem. Late in the process I started having the symptoms of a failing governor pressure solenoid....searching for gear on the 1-2 shift under slight acceleration. The truck was still under warranty so I took it to my dealership. The technician was highly experienced with the 48RE on diesels but had no experience with them on an SRT10. He knew when he changed the solenoid I had a shift kit in the truck. In an attempt to help on the WOT shift problem I'd related to him, when he changed the solenoid he also made an adjustment (thumbwheel on the valve body) that increases line pressure believing that would help with shift firmness/shorten the duration. When I left the dealership it would not make WOT 1-2 or 2-3 shifts at all. It would run up against the rev limiter and just hold. I went back immediately and he returned the thumbwheel to the setting it had been adjusted to when the shift kit. When I left the dealership there was no searching under slight acceleration for the 1-2 shift, but of greater note the shifts would consistently happen exactly where they should WOT 1-2 and 2-3 with no symptom of hitting the rev limiter. For 3-4 months of many WOT runs I had no problems. Afterwards I started having periodic rev limiter symptoms, Recently I've started to get the search on 1-2 light acceleration shift again. My truck has right at 40,000 miles on it. All indications are that my transmission is in great shape. It's just time to change the solenoid again. All sources say it's a consistent weak link. I've not been able to find an aftermarket upgrade part. The pan has been off it 3 times, with the bands professionally adjusted each time. Early June I put an SCT tune on my truck when I added the Roe s/c. The SCT made the shift problem no better and no worse. Because of the problems folks are having with Viper engines blowing, amd because of minimal performance loss (great low-end torque fro Roe) from having shift points lowered, I talked with Sean about lowering my shift points to the 5200-5400 range for the 1-2 and 2-3. He made a comment when we talked that anything that raises line pressure on our trucks increases the probability of the shift points not being caught by settings in the tune, and the result of shifting higher shifts than expected from settings in the tune (how much depends on how much increased line pressure and condition of the governor pressure solenoid).
So, my opinions are:
-your problem is increased line pressure from the tune versus condition of your governor pressure solenoid.....changing the tune won't fix it/reducing or eliminating torque management and increasing line pressure is common to all aftermarket tunes I know of
-if you don't have a shift kit, replacing the solenoid will fix the problem temporarily
-if you do have a shift kit and the thumbwheel setting is correct for the kit, replacing the solenoid will fix the problem temporarily but "temporary" with the kit installed is shorter duration than without the kit because of the dual source (1 shift kit, 1 tune) increases of the line pressure resulting in exposing the solenoid weakness sooner
-with stock tune and no shift kit the first symptom of a failing solenoid will probably be the 1-2 shift hunt under light throttle
-but with increased line pressure from tune and/or shift kit the WOT shift lag like hitting the rev limiter will show up first, followed months later by the light acceleration 1-2 shift hunt.
I was already having my fluid and filter changed prior to each cool weather race season. I'll just have the soelnoid replaced each time also, and may consider a 6 month instead of annual frequency. Going fast costs in time, money, and head scratching. I'm having the problem you describe. I'm getting my solenoid changed with my fluid and filter change later this month in prep. to start racing about Columbus day. No doubt that will fix my problem.
I really believe changing your governor pressure solenoid will eliminate your shift problem. Get the fluid and filter changed and bands adjusted when you do.
Best to all,
oldguy
