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Discussion Starter #1 (Edited)
Hello all

I've got a 98 S500 with 110k on her that I acquired four months ago. Everything has been going well until a week ago. I noticed that she does not shift up into the fifth gear consistently.

Lets say I'm on the highway and I sprint up from 50 to 75 and get off of the accelerator, normally the RPMs would quickly go back to 2000 or so. Now, they just hang out at whatever they were at (usually between 3000 and 5000) and slowly come down. If I turn on the cruse control, the overdrive gear immediately kicks in and all is well. If I get into the pedal again, I have to re engage cruse control to get back into the top gear. This problem happens about 90% of the time while driving and happens at low or high speeds, cold or warm engine. The cruse control activation trick works EVERY TIME. I thought it could have been the switch inside of the shifter, but if I am in cruse control, I can shift between 4th and 5th with no problem.

This issue started one day out of the blue without any issues beforehand. :dunno:The tranny fluid, filter and pan gasket haven been changed with OEM parts. Shifting is smooth - no noises or clunks when shifting gears; reverse and drive engage instantaneous. No check engine light (but I didnt expect one). I know the best thing to do is to get it on Star Diagnostics, but I'll be damned if they tell me "no issues!"

Any ideas as into the what is going on here with my 722.6 :confused:
 

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Hello all

I've got a 98 S500 with 110k on her that I acquired four months ago. Everything has been going well until a week ago. I noticed that she does not shift up into the fifth gear consistently.

Lets say I'm on the highway and I sprint up from 50 to 75 and get off of the accelerator, normally the RPMs would quickly go back to 2000 or so. Now, they just hang out at whatever they were at (usually between 3000 and 5000) and slowly come down. If I turn on the cruse control, the overdrive gear immediately kicks in and all is well. If I get into the pedal again, I have to re engage cruse control to get back into the top gear. This problem happens about 90% of the time while driving and happens at low or high speeds, cold or warm engine. The cruse control activation trick works EVERY TIME. I thought it could have been the switch inside of the shifter, but if I am in cruse control, I can shift between 4th and 5th with no problem.

This issue started one day out of the blue without any issues beforehand. :dunno:The tranny fluid, filter and pan gasket haven been changed with OEM parts. Shifting is smooth - no noises or clunks when shifting gears; reverse and drive engage instantaneous. No check engine light (but I didnt expect one). I know the best thing to do is to get it on Star Diagnostics, but I'll be damned if they tell me "no issues!"

Any ideas as into the what is going on here with my 722.6 :confused:
the check engine didn't turn on? on my 97 the check engine light turned on everytime my tranny had a issue. the star diagnostics just points what it thinks the issue its not always 100%. mine was just a tranny leak that caused alot of issues. have you checked the fluid level? makes a difference, when its low 5th wont engage.
 

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The "D" contact switch (housed in the shifter assm) is what most likely is the issue. Try pushing (and holding) the shifter over to "D", my bet is it will go in OD everytime.
 

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Discussion Starter #4 (Edited)
The fluid level is 100% correct and the transmission filter and gasket have just been replaced - no leaks.

HOWEVER, I am going to drive the W140 tomorrow and manually force the the shifter over to the "D" "all the way" and see if that makes a difference. I already have a new switch just sitting and my radio "keys" arrived today.
 

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sometimes these shifters have issues. on the w208 i got my girlfriend the shifter assembly actually was messed and the D position had two spots and one would engage fifth and the other wouldn't
 

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As the above replies,,it has to be the switch in the shifter.

It is not an overdrive on a 722.6 box, just 5th gear
 

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As the above replies,,it has to be the switch in the shifter.

It is not an overdrive on a 722.6 box, just 5th gear
some people actually consider it as an overdrive because its suppose to engage around 37mph.

but yeah it is a gear not overdrive, just explain how people think.
 

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You may have a damaged segment switch or a bad OD switch! Both are located on the shifter! Just for shit s and giggles the next time it drops out push your shift lever to the right against the gate and if it upshifts one or both are bad!! easy fix!! First thing I had to fix on mine!! Keep us posted on yer progress!!!


Smokie
 

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Discussion Starter #9
Pressing on the shifter does not yeild any result (eg. if the car is in 4th and should be in 5th, forcing the shifter all the way to the right does not have an impact), nor does "giggling" the shifter from 4 to D.

When in cruse control at 5th gear, switching the shifter from 4 to D and back does cause the car to shift appropriately - every time. Does this mean that the switch is not bad??

Also, I took out the wood dash etc, but could not get to the driver side mounting screws for the shifter assembly - the rear a/c duct is covering it. Alldata DIY says that the entire center console must come out!! Is this what everyone else had to do?
 

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Is there a how to on the segment/od switch????

You may have a damaged segment switch or a bad OD switch! Both are located on the shifter! Just for shit s and giggles the next time it drops out push your shift lever to the right against the gate and if it upshifts one or both are bad!! easy fix!! First thing I had to fix on mine!! Keep us posted on yer progress!!!


Smokie
I have to give it a go....if someone has instructions much obliged:)
 

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When in cruse control at 5th gear, switching the shifter from 4 to D and back does cause the car to shift appropriately - every time. Does this mean that the switch is not bad??
On a flat level surface with the cruise on, just barely coasting/under power, what is you rpm at 60mph?
 

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Discussion Starter #14 (Edited)
Update!! - Not Fixed Though!

I picked up a Star Diagnostics C3 kit online to see if I had any codes stored - nothing for the engine or EGS (transmission).

After further diagnosis, here is what I've discovered:
  • The fifth gear is not my problem - the problem is upshifting. When starting the car, the first 6 minutes of driving will cause the car to hold the 3rd gear when it should be shifting to 4th & 5th gear (eg getting on the highway and getting to 70mph). The RPMs will be around 3.5k RPM. After driving like this for 6 minutes, the car will upshift into 4th and 5th and the issue does not come back until the car has been turned off. Once the car is turned off (and can be immediately turned back on) and turned back on, the issue is back - no shifting beyond the 3rd gear for 6 minutes.
  • Within this 6 minute window, I can apply cruise control and the car will upshift into its correct gear without any problems.
  • The shifter assy is communicating its proper position with the TCM (DAS will tell you what position in which the shifter is physically in and it is correct every time.
  • When using DAS, the TCM will display the actual gear and the target gear (1-5). Eg - when causing the car to downshift (getting on the accelerator hard to go from 55 to 75). If you are already in the 4th gear and hit the accelerator, the target gear will show 3rd, actual will be 4th for a split second and then the target and actual will match - this is the correct reading. When my car is stuck in 3rd, 3rd is reading out as the actual and target gear - so the transmission does not think that its doing anything wrong.
  • Resetting the transmission adaptive data did not solve the issue.
I think we can all agree that this is something electronic, but what? :confused:

After the 6 minute rule, everything is fine. Cruise control always works no matter what. I also looked in the "coffin box" - shes bone dry. New OEM fluid and filter recently installed; all shifts are smooth with no cluncks or R/D engage delays.

I'm thinking that something on the conductor plate is bad, but anything there would throw a code (wouldn't it)? :confused: Or perhaps the TCM is not well.

Thoughts? :surrender:
 

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I will go for conductor plate,, not that expensive and a quick fix hopefully.

Do check that the pilot bush is not leaking sending fluid up the wiring harness into the box ECU, though this does not harm the ECU the 2 CAN wires are signal only and any poor contact here will give strange faults
 

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Discussion Starter #16
I will go for conductor plate,, not that expensive and a quick fix hopefully.

Do check that the pilot bush is not leaking sending fluid up the wiring harness into the box ECU, though this does not harm the ECU the 2 CAN wires are signal only and any poor contact here will give strange faults
Thanks. The ECU box is dry, but we did not change the bushing on the plug - will do that next go around.
 

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Thanks. The ECU box is dry, but we did not change the bushing on the plug - will do that next go around.
If you can spray the connector on that ecu with a good non drying switch cleaner, the CAN pins (2 end ones) can give false signals and possibly a fault like yours.

This is a known problem in WIS and affected the 129 as well, where it could just lock or pass on any gear and you never knew when
 

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Thoughts? :surrender:
I think you are on the right track here. You have ruled out several scenarios by
saying its getting normal after 6 min. and that it has no error code.
As you also mention that the transmission also wants - are being told by the TCM -
to be in 3rd and is in 3rd, I think you should instead concentrate on the input to the TCM.

I, again, have read one of the 722.6 descriptions out there, this time for the W202,
but is the same in every way;
Transmission

Every car with 722.6 have delayed upshift the first minutes after startup.
Now, the reason of this is not completely/absolutely known, but it sure has to do with
one, if not all, of the following; ATF temp, engine coolant temp and/or temp of cats.

If you look at this page, and for the part about "Shift Program";
Electrical/Electronic
you'll read that amongst influencing factors are;

Catalytic converter warm-up
Cruise control operation
Low and high ATF temperature

So, my guess is, that you have normal operation, that perhaps
times out at 6 min, since the desired ATF temp is not reached.
Or, that its completely normal, since it cannot measure the
temp of the catalytic converter.

Since Cruise control operation is also in this equation, it could
explain that you are having normal operation when using it.

Can you do a reading of the ATF temp on the DAS?

(Personally, I hardly ever reach roads with potential to go fast enough
for 4th and 5th until well after 6 min of driving...)

br,
syljua
 

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Delayed upshifts is to warm up the CATs as soon as possible. this is taken from the temp in engine.

the CC uses a speed signal to work things out,,so does the box, the use of CC could wake up the CAN and the speed signals in the box,,it is worth cleaning the CAN connections
 

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Discussion Starter #20
Update II

Everyone, thanks for the suggestions thus far.

I decided to take another look at the TCM (remember my coffin box is dry and clean)...then I unlatched the connectors!! Not very much, but ATF was on the connector and the recessed fitting. I cleaned these guys out with electronics spray and it seems that the car shifts smoother, although this could all be in my head. :bowdown:

I've already picked up the new connector that goes at the transmission and will be installing it in the morning. The issue itself is not yet solved.

I will report my findings...
 
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