1994 E320 - transmission slips when starting off in 1st - PeachParts Mercedes-Benz Forum

Wayfarer · #1 06-05-2012, 01:19 PM

Searching through the archives, tells me that my symptoms are not all that common. So here goes...

1994 E320 with 109K miles, new to me a few months ago. From all accounts very well serviced, proper stickers, including a recent service sticker on the transmission itself. Just to be absolutely safe and to start with a known baseline, I had the transmission fully serviced by my trusted indie, full drain including TC, new filter, the works. Afterwards I noticed that the transmission seemed to occasionally slip for a moment then engage when starting from a complete stop, especially when cold and/or after shifting to D from reverse. It slips for just a moment, maybe a half second...not even enough time for the motor to rev...then gently clunks into gear and off I go. Only happens when I shift from R to D or when I roll a stop sign. All other shifts 2-3, 3-4 are normal. It semes to not do it much when car is totally warmed up, although it ocassionaly still does. It is most pronounced when cold in the morning, always doing it after I back out of my driveway and shift from R to D first thing in the morning on my way to work.

After driving it like this for a week or so after the transmission service, I checked the fluid level and found that it was waaay over the full mark. Thinking I had found the culprit, I drained a full liter before it came back down to within the marks. Yes, I measured it fully hot, in park, idling, etc.. Now the fluid level is right on the money. However, the problem persists, and if anything it is even a little worse now that the fluid level is at the correct level.

The clunks are not at all violent but clearly perceptible and somewhat disconcerting...I know I am not doing the driveline or transmission any favors by driving it like this...although not being too bad, I could probably drive it like this for a long time before anything real bad happens. It doesn't happen all the time, but is intermittent, except when cold when it does it pretty much all the time. I drove the car about a month (1,000 miles) before the tranny service and did not notice this problem until had the transmission serviced. Otherwise it shifts perfectly. 2-3, 3-4 are crisp, perfect really, and it goes right into reverse with practically no delay. Reverse works great, no issues there. When I bought the car, I thoroughly tested the transmission and it worked perfectly then. This is my 5th W124 and I did not want to deal with transmission issues yet again, so I was very careful this time making sure the transmission was good...I digress...

Any ideas what is going on? My only thoughts are that something (dirt) got plugged up in the valve body during the recent transmission service. I don't think the overfill would have caused a seal to blow or other damage. When it was overfilled, it did not foam or overflow out of the transmission. Or maybe clean fluid dislodged something or otherwise altered the function of the transmission?

Is there any point to pulling the pan and say checking/replacing the B2 piston and or dropping the valve body and thoroughly cleaning it? Perhaps incrementally adding in fluid to see if there is a sweet spot it likes a little above the max mark?

Love this car. First M104 after already enjoying the M103 and M119. I did not know what I was missing. The late M104 E320's really are a joy compared to the early 300E's (another great car by any measure). The transmission is much better on these cars (save for my minor issue discussed here).

Thanks.

Darren

mbdoc · #2 06-06-2012, 08:51 AM

Slippage on a trans like that is almost always related to a mis-adjusted main band.

MB even issued a 'bulletin" on that adjustment.

Requires removal of B2 piston & measuring of band clearance.

Wayfarer · #3 06-06-2012, 10:43 AM

Thanks Doc. Next time it's in for service, I'll let my indie know abut that. Looks like pulling the B2 piston and having a look is in order. It's either the band or the piston itself, I figure.

Yesterday, I drove it all over the city running errands and as long as I was somewhat gentle when starting off, it didn't slip at all. Only when I accelerated rather smartly, did it slip a little. And when I really tromped on the gas, it chattered for a second or so from a stop. So until I can bring it in, I'll just go easy on it.

Except for the first moment after starting from a stop, this transmission shifts perfectly. I am quite impressed with the changes MB engineers made to the very late W124 tranny's compared to the early to mid production W124's I'm most familiar with.

I'm also going to try adding a bit of fluid back in. My instincts tell me it could be low pressure at idle, although that wouldn't explain why it did it with the fluid level too high. Worth a try.

disley · #4 06-06-2012, 10:11 PM

Using the correct ATF is also important.
As it started after the fluid was replaced.

Wayfarer · #5 06-06-2012, 10:15 PM

Success! (I think...) I added 4 oz. of ATF and there is no more slipping in 1st. On the dipstick, this brought the fluid level from about 1/3 of the way between the min and max (on the "hot" 80C scale) to just a hair below the max mark. Now no more slipping at all, even when I tromp on it from a full stop. Throughout all of this, I carefully checked the fluid level at hot idle in park, first by pulling the dipstick, wiping it with a lint-free cloth, putting the dipstick back in, then out, and checking for the lowest spot on the dipstick that had an obvious dry spot (this is my normal procedure of many years).

I drove it all today around town again on errands, and not a single problem.

Operated perfectly. Even when cold first thing in the morning and then again mid-afternoon after the car had been sitting most of the day. Even when trying purposefully to get it slip with quick starts, tromping on it while rolling stop signs, trying everything to get it to slip or chatter.

My theory is that with an older transmission, possibly with a worn or sticky B2 or worn main pump, the tranny needs all the fluid it can get to operate properly, without going over the max mark which would start causing other issues.

If this didn't fix the problem, I'll post back, but I think this has got it licked. Guess everybody was right, this transmission (a 722.369) is very sensitive to fluid level, and apparently even more so as it ages.

Wayfarer · #6 06-06-2012, 11:15 PM

Quote:

Originally Posted by disley

Using the correct ATF is also important.
As it started after the fluid was replaced.

Fluid is Castrol Transmax Dex/Merc Dextron III. There are no less than 7 varieties of Castrol ATF, not exactly making it simple to pick the right type! My indie uses Dex/Merc which is approved for Dextron III applications such as the 722.369.

When I have done my own fluid changes, I've simply used Wal-mart Dextron III with good results. Supposedly the Castrol is better.

I think the overfill and then slight underfill messed with the pressures enough to cause my issue. The fluid level was right at the high mark before the fluid change, btw, ever so slightly higher than where it is now.