722.6 valve body question
 

1997 E320 W210, approx. 180,000 miles. Trans shifted fine, however once in a while it suffered from a slight flare at the shift from 3 -> 4. I am in the process of servicing and just checked my log; this is the 3rd fluid change to date. I have drained the pan, torque converter, and radiator cooler (had to remove radiator to replace serpentine belt). All in all I believe I got about 6.5 quarts of the fluid out of there. It was very dark and resembled motor oil with a reddish tint, but did not smell burnt. The pan was very clean, with no pieces of metal.

I am replacing the pressure regulating spring in the valve body, 2nd from the back, passenger side under the plate with 12 torx screws. After removing the old spring, it appears to be a hair bit shorter than the sonnax replacement. I did not measure it yet, but it's very very close to the same length of the new spring. I was disappointed that it was in once piece; I was hoping to find it either broken or severly distorted. However, the spacing of the coils is irregular, with some being closer together than others. The instructions that came with the spring did say that this condition would warrant replacement.

I plan to button everything back up and fill with the proper Fuchs fluid, which I bought through FastLane. I also picked up the gasket and filter from FastLane. I'm hoping everything will be improved from here on out.

Has anybody else here experienced an occasional flare from 3 -> 4? It was very slight and would only occur when the tranny was hot. It was also intermittent.

I get a flare from 2-3 and 3-4 only under steady high acceleration. If I accelerate hard and let up before the shift point it doesn't flare.

Since your going through the trouble of dropping the pan, I recommend putting in a pan magnet which they started putting in for the later 98 on up models.

Where did you source your springs from?

Yes, actually that's what mine was doing. It would only flare when accelerating hard. Driving gently, it was fine. Only occurred from 3 -> 4.

My spring came from transmissionpartsusa.com. It is supposed to fix this condition.

I thought about the magnet, but my local dealer would have to order it and it was $30. I need to get this car back on the road. Besides, it has survived 180,000 miles just fine without a magnet.

I'm optimistic that my issue will be fixed.

Thanks for the info, Let me know if the new spring fixes your problem. I often thought that the flare problem was a weak spring since I am on my third trans fluid change.

The Mercedes pan magnet is not much more then the credit card style magnet with slots cut into it. My 92 Astro van came stock with a trans pan magnet and what I noticed is that most of the crud sticks to the magnet leaving the fluid looking like new.

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...

Glad to hear that your shifting problems are gone. I ordered the sonnax spring yesterday, hopefully my outcome will be the same.

The TSB I recall reading about filling the ATF to the very top line was a recommendation for people who complained about rough shifting. As long as your within the fill zone for the recommended temperature, I wouldn't be concerned about keeping the ATF fluid at the top mark.

UPDATE: About 65 miles on the car now, absolutely no slipping. And the shifts continue to get smoother as the transmission adapts.

I put the magnet in my 96 and when I got it I realized it was the same magnet that was in my 93 Ford Taurus. I'm sure its cheaper from Ford.

Part numbers for the spring and for the magnet would be very helpful...

Updated pan magnet # A 169 371 00 03. Available through Mercedes dealer.

Sonnax spring #68942-01. Available through transmissionpartsusa.com.

I replace my spring last Friday and after two short drives, I no longer have any slipping. My spring also was not broken but had uneven spacing, it appears that the coils were spaced further apart in the middle.