S420 Jerky Feeling - PeachParts Mercedes-Benz Forum

mbworld · #1 09-09-2006, 10:15 AM

My 1996 S420

When I reduce speed, for example coming to a stop light or stop sign, I noticed a jerk.

But this jerky feeling is not there when I accelerate. Any comments on what might be causing this jerky feeling welcome.

Sounds to me like the gear is shifting to a lower gear.

A. Rosich · #2 09-09-2006, 02:35 PM

I would check two things: your engine mounts and your transmission fluid.

If the engine mounts are gone, put in new ones.

If you have not serviced the transmission, have it done a.s.a.p. (oil and filter change) Disregard the theory about the oil for the 722.6 being set for life. And remember to use only the authorized M.B. oil and be sure that the level is fill up to the top mark. Also, be sure the level is properly checked after refill at the appropiate oil temperature.

mbworld · #3 09-09-2006, 07:14 PM

Thanks for the replies.

I wish to replace the transmission filter myself. Would anyone suggest or provide a link on how to replace the filter on the 1996 S420.

engatwork · #4 09-10-2006, 10:22 AM

Quote:

suggest or provide a link on how to replace the filter on the 1996 S420.

Drain the torque converter, drain the pan, remove the pan, replace the filter. Assembly in reverse order.

softconsult · #5 09-10-2006, 11:40 AM

Does a '96 S420 have the 722.6 transmission?

Steve

Arthur Dalton · #6 09-10-2006, 12:10 PM

Quote:

Originally Posted by softconsult

Does a '96 S420 have the 722.6 transmission?

Steve

722.622

mbworld · #7 09-11-2006, 11:22 AM

I have the pan and gasket for the transmission in sight.

1. Where is the drain plug for the torque converter ?
2. When refilling the fluid does one have to use the same path to fill both parts (i.e. torque converter chamber, & the pan filter chamber).
3. The "path" I am referring to above is the path through which I would insert the dip-stick (MB dipstick) to measure the level of the fluid in the transmission.

softconsult · #8 09-11-2006, 12:12 PM

The drain for the Torque Converter is not necessarily visible. You have to rotate the engine in the normal direction( important) in which it turns until you can see the plug in the opening in the the casting. You do this either with a socket on the cranskshaft nut at the front of the engine or by levering a large screwdriver gently against the torque converter to move it around. It is an internal allen. You will need a allen stub in a socket. Can't recall the size.

Yes, you pour the fluid down the dipstick tube.

Sounds like this is very new to you. Do not crawl under there unless you have the car safeguarded with proper jackstands!

Do a search on this forum and you will find step by step instructions. Do not wipe the dipstick, or the inside of the pan with paper towels. Use only something lint free. Be careful to not get any loose particles of dirt inside the transmission.

Buy a small funnel that will fit the top of the tube.

You will find that the there is a locked cap on top of the dipstick tube. Press the red thing down to unlock it. You are supposed to buy a new cap. I just re-used the same one. Press the red thing out and put it back in the top. Works just fine.

Good Luck,

Steve

mbworld · #9 09-11-2006, 06:53 PM

Steve,
That is very helpful. Thank you.

I will have to make an effort get started on this job.

rchase · #10 09-12-2006, 04:41 AM

Quote:

Originally Posted by mbworld

Thanks for the replies.

I wish to replace the transmission filter myself. Would anyone suggest or provide a link on how to replace the filter on the 1996 S420.

I personally would not reccomend doing the service yourself. Its really messy and you need a very CLEAN place to do it. Dust and debris and dirt are not helpful to your transmission. Additionally the 722.6 requires a special dipstick tool and is tempature critical and requires and infared themometer in order to check the tempature of the transmission. Having it done at the dealer and doing it yourself works out to be about the same if you have to buy all the tools needed.

I do a lot of DIY work but I draw the line at certain messy and difficult jobs.

Ron in SC · #11 09-12-2006, 08:04 AM

I just did this job for the second time on my 1999 ML 320 which now has 117K miles. I do have the special tool and an infared thermometer. This last time I did put the magnet in the pan, although there was zero metal, shiney particles, or slug.

What I do to make very little mess is as follows:
-drain torque converter first and hang a 5 gallon bucket underneath converter and keep it as close to converter as possible so no splash.
-put bucket under transmission pan and drain it out.
-put drain plug back in pan and let it sit overnight.
-remove plug and drain what is left.
-put drain plug back in pan and carefully remove pan, it will still have fluid in it.
-pour into bucket, and then measure total fluid removed, mine measured a couple of oz. short of 7.5 liters.

I put in 7.5 liters and with temp of trans fluid was at 28 degrees C with the engine running after 3 mins. On the special tool it measued about 1 mm below the second mark for what temp should be with fluid temp at 25C.

mbworld · #12 09-16-2006, 10:02 PM

Taking the car to a dealer is okay if it is a major job.

I agreed to buy the dipstick and approached a dealer in Maryland and they said it would take 4-6 weeks to get the dipstick. Indirectly what the parts fellow was asking me to do was to take the car to their service department.

So I called up another dealer in the next town about 40 miles away and he said he can have the dipstick for me to pick it up in 2 days time.

Well would you tell me which dealer you would trust your car with ? The first or the second ?

To surmise the story, I have decided to seek the help of folks on this forum to get the best advice and get the job done on my own.

Once again thanks all who did contribute to this thread.

dkveuro · #13 09-16-2006, 10:50 PM

Quote:

Originally Posted by mbworld

My 1996 S420

When I reduce speed, for example coming to a stop light or stop sign, I noticed a jerk. ......................

Check the MAF.
The spec' for the MAF at idle is 10grams per second ...if it is out of range, engine will add incorrect fuel amount at low rpm's where the 'cut fuel on overrun' programme turns fueling back on again at target speed...usually 1300 rpm.

Also....the engine bay harnesses insulation on these cars turn to powder, causing no end of problems.

.

rchase · #14 09-16-2006, 11:57 PM

Quote:

Originally Posted by mbworld

Taking the car to a dealer is okay if it is a major job.

I agreed to buy the dipstick and approached a dealer in Maryland and they said it would take 4-6 weeks to get the dipstick. Indirectly what the parts fellow was asking me to do was to take the car to their service department.

So I called up another dealer in the next town about 40 miles away and he said he can have the dipstick for me to pick it up in 2 days time.

Well would you tell me which dealer you would trust your car with ? The first or the second ?

To surmise the story, I have decided to seek the help of folks on this forum to get the best advice and get the job done on my own.

Once again thanks all who did contribute to this thread.

Good luck. Just be careful not to get any debris or dust in your transmission. The 722.6 is not the most robust Mercedes transmission made.

tinypanzer · #15 02-27-2017, 02:07 AM

Quote:

Originally Posted by dkveuro

Check the MAF.
The spec' for the MAF at idle is 10grams per second ...if it is out of range, engine will add incorrect fuel amount at low rpm's where the 'cut fuel on overrun' programme turns fueling back on again at target speed...usually 1300 rpm.

Also....the engine bay harnesses insulation on these cars turn to powder, causing no end of problems.

.

Ok, so I hate to reply to a thread from 2006, but here I go.. This is the only post I could find that describes exactly the problem I am having.

1997 S420 with a recently rebuilt trans. My local indy (former dealer tech) rebuilt it himself, and I have ZERO reason to doubt his abilities based on his track record. I bought the car from him last week.

I don't think the problem is necessarily transmission related in my case. Being a w126 owner, I have experience with what happens when the idle circuit microswitch on the throttle assembly acts up or gets out of adjustment, the motor fight with you a bit. This is sort of what it feels like with my 97 s420...

I can reproduce it fairly easily, but it doesn't do it every time. Also, I don't know if it's my imagination or something else I'm doing, but I feel as though if I let the accelerator pedal up abruptly, to 'snap shut' if you will, that the problem doesn't happen.

The trans basically has a couple hundred miles on it at this point - freshly rebuilt. I am VERY hesitant to go back to him with this issue if it's not transmission related. If it's the MAF, I can tackle it easily.

Is this a known issue, where you get a back-and-forth lugging or jerking when gradually decelerating? I can only find a few mentions of this on the web at all, but no real answers. The suggestion that it might be the MAF is intriguing. Are there any other throttle related parts I should check? The wiring harness should be fine, it looks great in the places I've inspected, and it's a 97 so shouldn't be an issue anyway.

The trans seems to work perfectly otherwise, smooth shifting and responsive. It's only as I near a stop sign or slow down gradually by trying to coast that it happens.