You can also try using some Lubegard red, it helps to keep the transmission working sweet. I added some to my W124 and its now quicker to shift into reverse. (not GM quick - but quicker by MB standards)

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)