UPDATE: NO SLIPPING anymore between 3 and 4. I have driven about 25 miles and gotten the tranny nice and hot, and have driven the car with both medium throttle and wide open, and there is no more slipping! The sonnax spring must have worked! I'm so happy! On a normal day, it would have surely slipped by now. The best part is that the shifts are barely noticeable now, whereas they were occasionally very harsh before the service, even "slamming" once in a while. Now I can't even tell it's shifting. I'm certain this is a function of new fluid of the correct type.

Using the dipstick tool, I am about 1 mm from the top 80 degree mark. IR thermometer reads about 90 degrees at the pan. I recall reading somewhere here about a TSB recommending fluid right at the top mark for best shift quality. I think I am going to drive for a week and then check it again. If it's still a hair low, I'll bump it up to the top mark.

This car now shifts like new. It's amazing considering it has nearly 180,000 miles.

I also changed the oil and filter while I was at it, and installed a new serpentine belt. I feel like I have a new car.

Now all I need is a new set of Bilsteins...

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280