1997 E320 Vibration - Page 2 - PeachParts Mercedes-Benz Forum

drbrandini · #16 01-17-2005, 05:30 PM

I know what you mean, sounds kind of odd to me also.

The car is going to the stealership for an oil change tomorrow...I'll see if they can take a look at it.

Thanks for your help Paul !

drbrandini · #17 02-01-2005, 03:09 PM

Quote:

Originally Posted by jcyuhn

If the vibration is related to engine RPM and not vehicle speed, then it's unlikely to be the center driveshaft bearing. The driveshaft turns at a specific RPM for any given road speed, regardless of which gear the transmission is currently in.

Given that your problem is RPM specific, I'd look toward motor and/or transmission mounts. Collapsed motor mounts are relatively easy to diagnose.

- JimY

Jim,

How do I diagnose a bad trans mount?

Ali Al-Chalabi · #18 02-02-2005, 01:08 PM

I would suggest it is very likely that the problem is what MB DOC posted about in the beginning. The touque converter lockup clutch will lockup on that car at about 35 mph hour in gear 5 and 32 mph in gear 4. The lockup clutch has a computer controlled slip at those speeds to isolate any drivetrain vibrations that may result. The slip under no acceleration should be equivalent to about 60 rpm at those speeds. If you are not getting the proper amount of computer controlled slip out of the lockup clutch and it is engaged then this may be the problem. The proper amount of slip should amount to just barely a needle's width over 1500 rpm at 40 mph at steady crusing speed with a constant throttle position and with the lockup clutch engaged. No slip and it would be 1500rpm at 42 mph. This small difference can cause a vibration.

Has the transmission controller been replaced? I know of at least one instance in which a 97 E320 without an updated controller would do this, new controller fixed the problem. At those speeds, is the torque converter lockup clutch engaged? If so, will inducing it to release eliminte the vibration?

drbrandini · #19 02-02-2005, 02:29 PM

Ali Al-Chalabi,

Thank you for your post. That sounds very familiar. I am not certain as to how to test the your theory though. I have recently purchased the car. I am still obtaining records from the two dealerships it was serviced at. At the time of purchase I asked if he had ever had any transmission problems. He told me the only thing he has done to the trans. is service it at 60k and 120K. The controller sounds expensive, is this so? Could it possibly be a DIY'r job? I was able to replicate the vibration in all gears, lower gear, lower speed.

Thank you again for your help,

Ali Al-Chalabi · #20 02-02-2005, 02:39 PM

Hmmm, torque converter lockup is only in 3rd 4th and 5th gears. If it will do it in all gears including 1st and 2nd, the lockup clutch may not be your problem. I believe a lot of transmission controllers were replaced under warranty for the 97 model years if there was a problem that was brought to the dealer.

drbrandini · #21 02-02-2005, 02:58 PM

well..Now that you say that let me check the lower gears to see if occurs again. I actually have to step out of the office for an hour so I will try it then and get back to you. Thank you again.. I really appreciate your knowledge.

I sure hope this doesn't turn out to be expensive.....

drbrandini · #22 02-02-2005, 03:59 PM

Well upon second inspection I think you may be correct. Definately noticable in 4 and 5th. 3rd is very faint. 2nd is just to hard to tell, may be non-existant. Do I need to get the codes pulled from the controller to know if its bad?

I'm scared to ask what it may cost to replace this thing.

I do know that the previous owner had the ext. 100K mile warranty and wasn't afraid to use it.

Ali Al-Chalabi · #23 02-02-2005, 04:13 PM

I don't think it will store a code. When you press on the gas enough to get some acceleration but not enough to downshift, does the vibration go away? For example, you are going down the road steady at 40mph in gear 5, slowly push the throttle open a little more until there is about a 300 rpm rise, but not far enough to downshift. This rpm rise would be when the torque converter clutch releases, but the transmission should still be in the same gear. Try this and see if the vibration disappears at that point. Again, when the clutch is engaged, it will hold the rpm steady and you will push more, the rpm will be steasy and keep opening the throttle until the rpm suddenly jumps about 300 rpm or so. This sudden jump will be when the lockup clutch releases. At this point the torque converter will be transmitting the driving force and won't transmit the vibrations.

I do not think the problem will cause any damage if it is the torque converter lockup clutch not slipping enough, it will be more of a neusience than anything if this is the problem.

drbrandini · #24 02-02-2005, 04:27 PM

Quote:

Originally Posted by Ali Al-Chalabi

I don't think it will store a code. When you press on the gas enough to get some acceleration but not enough to downshift, does the vibration go away? For example, you are going down the road steady at 40mph in gear 5, slowly push the throttle open a little more until there is about a 300 rpm rise, but not far enough to downshift. This rpm rise would be when the torque converter clutch releases, but the transmission should still be in the same gear. Try this and see if the vibration disappears at that point. Again, when the clutch is engaged, it will hold the rpm steady and you will push more, the rpm will be steasy and keep opening the throttle until the rpm suddenly jumps about 300 rpm or so. This sudden jump will be when the lockup clutch releases. At this point the torque converter will be transmitting the driving force and won't transmit the vibrations.

I do not think the problem will cause any damage if it is the torque converter lockup clutch not slipping enough, it will be more of a neusience than anything if this is the problem.

Your are correct !! the vibration will go away if I push the pedal a little to accel. or if I let off the pedal a little. It is very annoying. Is this something that can be corrected without doing a lot of r/r ?

Ali Al-Chalabi · #25 02-02-2005, 04:42 PM

Yes, if the problem is indeed what I was talking about then it is likely a computer control issue and not a mechanical issue with the tranny. I am not sure what exactly can be done to correct the issue, but I had a vehicle in the family that did the same thing and an updated controller cured the problem. It was replaced under warranty on the vehicle, though, so I do not know what the cost involved would be.

The 97 model year was the first year of the 5 speed electronically controlled 722.6 tranny. There were some issues, naturally, as it was a first year production run. One of the updates that came out for the transmission involved an updated transmission computer.

drbrandini · #26 02-02-2005, 04:53 PM

Thanks again for all your help ! I do appreciate it !

I am suprised this hasn't been changed out already! As the car is now at 148K.....hmmm. I'll check into It!