722.6 Tranny issue - PeachParts Mercedes-Benz Forum

muleears · #1 01-02-2008, 12:44 PM

The transmission in my 98 E300 is beginning to worry me. I bought the car with 148K mi. and no record of any tranny maint. The car now has 164K on it after only 4 mo. of ownership. I immediatly did a drain and fill (with filter) with the proper MB fluid. My concern is when I quickly go from braking to acceleration, such as quickly stopping then starting at a stop sign, there is a pause before the tranny engages. Very brief, probably less than one second, then somewhat firm engagement. Like I briefly put it in neutral then drive. I am very familiar with turbo lag and this is not it. It seems to be worse when cold. If I wait a full second between letting off the brake and accelerating all is fine. Am I witnessing the early signs of transmission demise? When the drain/fill was done the TC was not drained, but the fluid looked good and the pan was clean. I have the fluid, should I do another drain and fill? Advice is greatly appreciated.

Ethan · #2 01-02-2008, 01:43 PM

I have the same style trans in my C-class. the early five speeds did have a tendency to bang into first when deaccelerating - my car does it sometimes and had read about the bang issue either on this forum or a magazine car review.

Have you excluded the FLEX DISC on the drive shaft and even transmission/engine mount wear as a possible cause. Even knowing of cold/warm temps you describe.

How did you check the transmission fluid level during your change? infra-red thermometer and a MB dip-stick tool?

Does the issue occur with the gear selector in 4th-gear or when manually downshifting and holding a lower gear?

muleears · #3 01-02-2008, 01:55 PM

Thanks for the info. Ethan. The pause is after I hit the accelerator, not during deceleration.

Have visually inspected the flex disc, they seemed OK. The car does need motor mounts, I never put the two together. The bad mounts could cause this pause?

Fluid change was done by an indy with the dipstick tool, I doubt the temperature protocol was followed. I checked it at home (I have the tool also) with the car at operating temp, after a 40 mile drive. I assumed (I know) that this would be around 80*C. The fluid was a little low, by my checking so I added about 8oz. If the temp. was off when I checked it, it may still be off and causing my problem? From what I have read we are supposed to keep the level at the full mark, not between the two.

This occurs with the shifter in the normal drive position, I don't generaly shift manually.

So what do you think?

Ethan · #4 01-02-2008, 02:06 PM

Really bad motor mounts can cause drivetrain lash, but I don't know if this occurs on Mercedes

Some people say trans fluid level needs to be ultra-accurate on these cars.

To really dial into the fix wait till you get some more responses from seasoned techs, this may be a slow time on this forum, so be patient.

ALBERTO · #5 01-02-2008, 05:17 PM

Hi
I have a clk 430 with the same geraboxand when cold i have the same problem , the problem is only when teh car downshift between 2nd to 1 st.
to avoid this I normally swithc to W untill teh car is hot in this way the car does not downshift in 1st .
When i reaxh operating temperatore is wor^king fine and i switch again to S.
I think that tjhe only solution is update the software but MB wokshop is expansive here in switzerland.........

Parrot of Doom · #6 01-03-2008, 05:54 AM

In this pause, are the engine revs rising or do they stay the same?

OzC36 · #7 01-03-2008, 06:51 AM

Quote:

The fluid was a little low, by my checking so I added about 8oz.

Wow! That's a lot of fluid to top up after a servicing.

When you checked the AT fluid level, did you do it with the engine running, with the AT set in D and with the park (emergency) brake engaged?

muleears · #8 01-03-2008, 07:02 AM

Parrot: I don't notice the revs rising so I would have to say they stay the same even thought I have depressed the go pedal. The pause is so brief it couldn't rise much anyway.

Oz: Checked it in park with the engine running, thought that was proper. I ran it through all the gears before leaving it in park.

OzC36 · #9 01-03-2008, 07:22 AM

Sorry, yes, check level in P. You are correct!

I'm still worried by the amount of fluid you needed to correct the Indy's obvious "sloppy work". Is it possible that he "forgot" to change the fluid in the first place?

All I can suggest is another fluid change with a good quality synthetic fluid. If you are confident that has already occurred, take it to the real MB Dealer for a problem analysis and quote for "repairs".

Parrot of Doom · #10 01-03-2008, 09:48 AM

If the revs are not rising during this pause then I do not see how it can be the gearbox. I think it is more likely that the engine is shutting the fuel supply off under braking, and not restoring it quickly enough upon acceleration.

Its quite normal to shut the fuel off when braking, mine does it.

muleears · #11 01-03-2008, 10:17 AM

Parrot, that sounds exactly like what it is doing! It only does it when I slow quickly then try to quickly accelerate. Is this something I need to worry about? Can it be fixed? It is not a big problem, I was just worried that my AT may be crashing. If this is as bad as it gets and its not my AT, I can live with it.

Gilly · #12 01-03-2008, 11:03 AM

I'd get the fluid level checked again, sounds alot like low fluid, especially if you didn't experience these symptoms before the change. The only really GOOD way to check it is using the SDS, which uses the INTERNAL temp sensor, I don't trust the pan temp at ALL. Yes you want it at the max mark on the stick. Not OVER the mark, just maxxed out.
Anyone who has done this the correct way can tell you what a big difference there is even with only a 5 degree fluid temp difference.

Gilly