Magnuson SC Update

For those of you that have read the few posts that I contributed in the RIPP vs Magnuson shootout thread, you know that I've had my Magnuson installed on my 3.6 for almost a year and a half now. I live in Texas and I'm using the high altitude pulley. My 2012 4dr Rubicon is a heavy rock crawler with steel skids, bumpers, 40" tires, 5.13 gears, Dana 80 rear axle, Dana 60 front axle, etc... and the additional power from the supercharger was a welcome change. I did the install myself over a weekend in my garage. The only real complaint that I've had with the supercharger has been the poor shifting characteristics with my 5 speed auto. Magnuson told me that they couldn't crack the transmission control module (TCM) encryption, so they tried to work the engine tune to compensate. My work around was to manually shift or lift off the gas slightly to let it shift on its own. It was frustrating, but doable.

The reason for my update is to inform you that Magnuson now has a way to re-flash the TCM to make the auto transmission shift like it did before the addition of the supercharger. I pulled my TCM and sent it to them for the re-flash. I hope to have it back early next week. I'll post my findings after I run it for a few days with the re-flash. I just wanted to let people that had the auto transmission and for those with the auto that have been holding off on the supercharger purchase because of the shift issues that there might be hope on the horizon.

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Well after a week of driving around with the new TCM program, it is much better than before. It isn't perfect, but it is getting better the more I drive it. I think the adaptive learning of the transmission is figuring out how I like to drive and adjusting the shifts accordingly.

Prior to the TCM reprogram, the transmission held gears longer than I liked, so I had to manually upshift a lot. It also wanted to stay in second gear past 4k rpm under normal acceleration and usually wouldn't shift into third gear unless I lifted off the gas pedal or manually upshifted. Highway driving was just as bad because it rarely wanted to stay in overdrive. I'd manually upshift to get it into 5th gear and it would downshift back into 4th gear almost immediately at 60+ mph. Engine wear and mpg suffered because I was usually running between 3-4k rpms a lot on the highway.

After the TCM reprogram, the transmission wants to shift into the highest gear as soon as possible. Sometimes I'm taking off from a dead stop and the transmission shifts from 1st to 2nd to 3rd and then downshifts back to 2nd because I had to give it more gas to get moving faster. It is getting better because I've learned that it usually happens when I'm light on the gas pedal. If I give it a little more gas when I start to accelerate, the transmission will hold second gear longer before it upshifts into third and then it stays in third gear without downshifting to second. It still feels like the jeep is struggling to get moving while the transmission figures out which gear it should be in. I'm hoping as the transmission learns my driving style that shifting from 1st to 2nd to 3rd will get better, so it doesn't feel as sluggish trying to figure out if it needs to be in second or third gear. I've never had to manually upshift or let off on the gas pedal to get the transmission to shift now, so it is much better from that perspective. My jeep also stays on overdrive on the highway for longer periods of time, so now my average rpms while doing 65+ mph is about 2500 or 2600 instead of 3k+. Overall the highway driving experience is a significant improvement.

I haven't tried wide open throttle yet, so I don't have any updates for that. I usually don't drive that way unless I need to pass someone quickly. The SC is more for moving my heavy jeep than racing.

Great info, thanks for sharing. I have the Magnuson on an auto JK as well and am experiencing the same gear shifting issues you had, however i got used to them for now. but non the less good to know that there is an update in case I want a change.

Any updates since your last post, bo9roadking? Just curious if it's been steadily improving or if it hasn't changed.

The auto is shifting normally now, so it is like I'm driving my stock drivetrain with more power. Definitely happy with everything now that the transmission has stopped acting up. While driving on the highway, I can actually hear the whooshing of the supercharger boost kicking in on moderate inclines while the transmission holds in overdrive. In the past, the transmission would downshift into 4th or even 3rd gear and all I could hear was the engine rpms winding up. I no longer need to manually shift like I did prior to the transmission TCM reprogram. Much better overall experience.

Now that I can hear the boost instead of the engine rpms winding up, I don't have to rely on my boost gauge as much. I'm mainly using the gauge to monitor my air fuel ratios instead of verifying that the supercharger is actually doing something.

I've discovered the only downside now is the cost of using premium fuel and losing about 2 mpg. I can live with that for the increased power. :cool:

This is great news. This might be one of my next big mods and a fun project. :D