1997 c230 Transmission Problem
 

I have a 97 c230 that has only 50,000 miles and has been serviced regularly. The car is in excellent condition but I am having a problem with the transmission. It shifts nice and smooth but when you gas it and hit that downshift button the RPMs go up almost to the redline and then it slams into gear. Does anyone have any ideas on what this could be???

hard downshifts
 

it sounds like a sticky valve in the valve body or a clutch seal or clutch pack friction lining failure. Needs proff. diagnosis including check of operating pressures.

The symptoms indicate the releasing clutch (gear) is disengaging well before the engaging clutch (gear) is making up.

If it shifts well otherwise (both normal and full throttle upshifts and normal downshifts), almost certaintly a sticking valve.

without engaging the kickdown feature, what happens when you acclerate to over eighty mph. is there any hesitation?

Is the check engine light on?

these were similar to the symptoms on my 1998 C230 when my MAA mass airflow sensor went bad, what you described plus the high speed hesitation.

go to an AUTOZONE and have the OBDII codes rear if you get something like 0170 it may be the MAA.

Also it is time to have your transmission fluid changed.

Do a search on 722.6 transmission or on the early C230 trans, there have been some upgrades. But do what I said about the codes first.

nice car

There is no hesitation over 80. The car seems fine until I floor it or use the kick down. Once I hit that button the engine races until I ease off the accelerator then it kicks back into gear.

No check engine light, my code reader doesn't get any fault codes. I checked the atf and the level is fine but it is kind of brown colored. I'm going to change the fluid and filter and see what happens. Hopefully that will take care of it.

Make sure you use only MB trans fluid. You are just asking for trouble otherwise. It's a bit spendy, but worth it in the long run. I've seen early 722.6's that have broken snap rings inside the case and let the planetary set go loose causing catostrophic failure. There is also one common culprit spring in the valve body that will cause a hard third gear shift and will delay engagement of reverse. I agree that this is probably something to have the professionals look into, especially before you go and spend a decent chunk on expensive MB synth trans fluid which may end up getting partially or fully drained during necessary repairs anyways. The sooner you catch these things, the better.

I've had this very occasionally in my 1999 SL500 and it happened quite often in my 2000 C240 (W202). I found it happens especially when down changing from 3rd to 2nd.

Does it "slip" at all when accelerating hard away from a stop? If so, you may have a pressure control spring gone south.

The best thing you could do is get the car onto SDS and read the transmission adaptation values. That would be a good first step. Also, early build 722.6's are subject to many upgrades, and you should look into them. There is an updated valve body for 97's and some 98's as well as an updated ETC.

If you haven't been using MB specific fluid and setting the level properly (using SDS) then you can cause damage that way as well. I personally know one fellow that "Went his own way" with servicing his 722.6 and wrecked it.

In all honesty, 97-98 722.6's are not the best units, and those not fortunate enough to have upgrades done under warranty are probably looking at hefty bills.

I changed the tranny fluid / filter / gasket with the mercedes atf. No change at all. I am buying a new MAF sensor and hopefully that will fix it.

It does not slip at all???

Huh? Why? Is there a fuel trim code? Have you read the adaptation values? AMM's are not inexpensive. Have you solved the transmission problem and now you have a new running problem? I'm a little lost as to how you arrived at the AMM as the problem...

Did you use the SDS to set the fluid temp while setting the level? If not, how did you set the level? I have seen this procedure done, and without the fluid at 80C it's possible to get the fluid level VERY wrong.

The transmission problem was never solved. There is a shop locally that specializes in servicing and repairing only Mercedes-Benz. They changed the tranny fluid etc. for me so I assume they used the appropriate tools. The technician recommended that I try changing the Mass Airflow Sensor. He said that he knows of some cars that had the same problem and were fixed by replacing it so I figured what the hell. :confused:

I'm joining in this pretty late. I think someone already mentioned that the fill level and using the MB fluid is critical, and I wouldn't assume a transmission shop would be all that familiar with it, so you better have a pretty hefty bill for that fluid, it runs over $10 per liter (sold by the liter even here in the US), and requires a computer to monitor trans oil temp.
But in looking at your first post, you have to remember this is an adaptive transmission, but it is "instantaneously" adaptive. What you might want to experiment with is in a test-drive, try putting you foot down a little slower when you floor it and see if the shift quality is better. If you put your foot down very fast, the transmission will respond with a later, harder shift.

Gilly

Well I paid $150 for the change it was done using a computer. The tech road tested the car and told me that when this happens the car hesitates and seems to be searching for the gear. He says that it seems to be electrical not mechanical and he thinks a Mass Airflow Sensor might fix it. He doesn't speak good English so I have a hard time understanding him. Here is what I observed. It does upshift and downshift fine. The only time this happens is if I fully depress the accelerator like when passing someone on the highway or trying to move out of the way fast. It seems to shift better when I ease off of the accelerator after noticing the hesitation. It happens each time I floor it on the highway but never at low speeds. I understand how when you respond faster it shifts rougher but I am sure that is not the case here. I have driven a c280 and doesn't do this. This car has been in for all of its scheduled service appointments on time and has been very well taken care of. :confused:

How much was charged for the fluid?????
Just the fluid, not the filter and gasket.....

Gilly