Has anyone found a fix for this problem? The dealer had the gearbox rebuilt under warranty, but the problem still exists. The diagnostic computer does not see the problem and test drives by the dealer have not replicated it (happens maybe once a week or so). This problem does go away in winter mode (at the recommendation of MB Technician) but I do not consider this a "fix". Can anyone tell me what controls automatic downshifting? Is it a computer module or control valve system? Is it time for a trade-in?

I used to have a 99 320 which did the same thing, so I assume it is normal and not fixable. I have an 02 430 now and it does not do that.

When I was demonstrating running into the rev limiter in my 99 CLK320 it was mentioned that they had seen a valve that sticks in the transmission in some of the 99's. Maybe this stuck valve is the problem. They did replace the valve thinking it was the problem I was having (which it was not). They eventually replaced the transmission and I could still get the car to run into the rev limiter. They bought it back and gave me another CLK320. I can get it to run into the limiter less frequently than the first model but it still happens. I have never had a violent downshift to 1st though. The stuck valve thing came to mind. Hope it helps.

I know what your talking about IF your talking about a very HARSH gear shift, kind of like it just slamming into a gear very unsmooth like. You have to put it in Winter mode if your going to be doing alot of stop and go driving so it wont keep dropping into first. My car will do the exact same thing unless I put it in "w" mode so it holds 2nd gear.

My '99 CLK320 also does this fairly frequently. It kind of "slams" into a downshift from 2nd to 1st. Quite annoying and concerning!

Has anyone actually found the cause and fix for this problem or do we just live with this?

read two post above

My CLK320, is very sluggish in W mode (in the morning), but when I have it in S Mode its fine. After the car has warmed up then W Mode is fine. But no probs while driving, gear change is smooth as silk.

Is there any probs driving in W mode?

Any ideas?

N

The sudden downshift only occurs in Summer mode and only when decelerating (taking foot off accelerator) at a low speed (2 - 10Mph)

no such problem with my 2000 model, but my freind's 99 model has it and it gets very annoying after a while.

apparently, no solution to this bug

i thought i was the only one with this problem as well..ive been getting more and more frequent.never tried the W mode. Seems like this is a very common prob with 99 320's.

I have the same on my CLK320 2000

Hi there from London,

I have a 99 CLK320 Sport and I experience these occasional violent downshifts from 2nd to 1st (and very occasionally violent upshifts from 1st to 2nd).

I believe I have got to the nub of the problem, apparently it is to do with the MAS sensor needing replacing.

Do a search of <mas* sensor> on the UK version of this forum at

www.mbclub.co.uk and read more.

I have ordered the new sensor and will have it fitted this week and keep you updated on progress, however it is intermittent so I wont know if this problem is resolved straight away.

Thx

Sasha

I got the same tip from Mercedes so I am changing mine tomorow.
I will let you know of the results.

I had mine replaced today.

Gearshifting is smoth again.

If ur car is out of warranty, then you should try cleaning the Mass Sensor before considering replacing it.

All you need is a size T10 torx screw driver, and a can of ELCTRONIC CONTACT CLEANER solvent.

yes....don't bring your car to the stealership for a MAF sensor. They charged me $550 for something i could have done myself for under 100. *******s.

Even my puny 98 CLK 230 does a 2nd to 1st slam once in a while. Gotten used to it. If there are 3 other people in the car, it does not seem so obvious. Still ok after 6 years so no worries?

I used to have a Rover 216 coupe (Honda engine and transmission) that also did exactly the same thing. No problems with the car after 5 years.

The car shifted much smother after i changed the MAF and the violent downshift stoped.
Don´t by the MAF from a MB dealer they will charge you aroud 500-600 USD.
I bought mine directly from BOSCH and payed 270 USD.
You schould be able to do the same i guess.
Or call BOSCH and ask how is the closest Distributer for the part you need and you schould get the same low prise.
The Partnumber of the MAF is: 280217515
(this is for the European CLK 320 but I think i schould be the same in the US other wise th PN is printed on the MAF)

Best Regards
Jonny Larsen

Common problem, unfortunatly one of many that Mercedes will not admit exists. The ML 320 and E 320 including CLK 320 are having failures at an alarming rate.

Transmission servos transfer cases, fuel pump sending units, crank shaft pullies, tie rods, lower ball joints, and self lvling systems all are failing at a rate I have not seem before. Make sure you have a warranty on these cars and haunt the dealer till they fix them. I finally sold mine when the warranty expired and got an X5. At the time I sold my 99 CLK I was experiencing the transmission problem, I had already had the fuel tank senders replaced, my crank pully was seperating and I had the lower ball joints replaced. The interior rattled from almost every panel and the dash in the center was making some strange noise when the weather got hot.

I hate to sound negative, but Mercedes quality is not what it once was, so keep your warranty up to date, I assure you if that crank pulley lets go it will be at least 2500.00 to fix, making a warranty easy to justify.

I also notice this exact same problem. Can someone tell me exactly what needs to be replaced/cleaned and how to do it?

I've got a 430 and I can say I've had about 20 instances (in the past 2 mos ) where I have had a violent downshift... I am hoping to find out if the MAF is covered under an Extended Warranty.

I used to have a 2001 BMW X5 4.4 and it had a reasonably logical shifter... If you were well into the redline, it wold not shift into the 1 gear... I've damn near hit the windshield a couple times getting used to it...

I have the same problem on my European 2001 CLK 320 .
Is this because of the MAF? Is it possible to clean it? and how? thanks

my car is doing the same thing--it slams from second to first gear when deaccelerating.

this is the second transmission--the first went out at about 70,000 miles. the transmission shop tells me that the gear position sensor is bad--which is causing high pressure in the transmission--which might be why the first transmission went in the first place.

anyone ever replace a GEAR POSITION SENSOR? the independent shop want $600 for it--

Not sure about any gear position sensor. When was the last time your fluid was flusheD?