Magnuson is still working with Diablo to get the auto transmission to shift correctly. I've had my Magnuson on my 2012 JKU for about 3 weeks. The surging is fixed, but the transmission still requires lifting on the throttle or manually up-shifting unless you want the rpms to wind up higher for it to shift on its own. It winds out higher than it did prior to the SC install. The shifts are usually between 3k-4.5K rpms when it shifts on its own if you have moderate throttle applied. Mild throttle shifts as it did prior to the SC install except the shift from 2nd to 3rd gear. That shift might still require lifting off the throttle even at mild throttle. The shifts are tolerable, but could be smoother.
The only real issue for me is driving on the highway. At highway speeds, the transmission doesn't like staying in overdrive unless the jeep stays on level ground. I'm at about 900 feet above sea level. Any incline that requires mild throttle input to maintain speed will cause the SC to gain boost. I think the boost makes the transmission think that I hit the gas to pass someone, so it downshifts one or two gears depending on how much throttle I've added. If I hold the throttle instead of adding throttle to keep the transmission from downshifting, I'll lose about 5 mph to get over the incline, but the transmission stays in overdrive. Needless to say, I'm not using cruise control or my transmission would rarely get into overdrive.
One caveat is that my jeep is heavy, so I need more throttle to get it moving and keep it moving. The weight might be the issue because I don't think Magnuson and Diablo are using test jeeps with 40" tires, D60 and D80 axles, with steel bumpers and skid plates.
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