What is the kick down supposed to feel like?

[Sdemon]

Hi there

I have an R129 500sl with the M119 engine. Since I have never owned one before I’m trying to understand if there is something sluggish about my acceleration. I’ve read about the kick down feature. Mine is equipt with the 4 speed auto gear box.

The issue is when I floor it, I don’t get a sudden surge in acceleration If feels like it churns to get into speed. At times when I accelerate, I hear a low and deep thump which I assumed it was the car dropping into gear but I’m no expert. In addition should there be a definitive click which you can feel in the pedal when the kick down sensor is activated because I feel nothing.

questions are:

1) should the acceleration be impressive for a 5.0 litre engine
2) what is that thud that happens
3) should I have a definitive click felt from the sensor?

The car has had the engine wiring harness and the wire to the throttle body replaced. New sparks, new oil, new filters, new seals, ignition parts all done. Iv examined the rubber lines and they all seem intact and connected.

appreciate your expertise in the matter

 

[gsxr]

1) Yes
2) When the kickdown occurs, the RPM's should increase substantially (i.e., from 2krpm to 4k, approximately)
3) You should feel a distinct "click" when the switch is engaed below the pedal. You can test & listen for this with the engine off.

BTW, what year 500SL do you have (129.066 or .067)?

From a stop, acceleration should look like this, approximately (E500E shown in video).

 

[gerryvz]

Well, the kickdown function should be EXACTLY the same as if you used the gear lever to downshift to a lower gear from "D." The performance and behavior should be exactly the same.

The kickdown switch should indeed provide an audible "CLICK" when depressed, and you should feel the downshift before the car begins accelerating. You are just controlling it with the gas pedal, rather than the gear lever.

You can test the kickdown switch electrically to see if it is working correctly. There also may be an issue with the kickdown mechanism on the transmission, but I'd first start with the kickdown switch.

There are a number of threads on the topic -- have you searched for info?

500E - Kickdown stopped working | Transmission and Driveline

While driving my 1993 500E to a paint shop for some touch ups today, I noticed that the kickdown had stopped working. I read fault codes with the blinker - zero fault codes. Is the kickdown-switch the likely fault, or any other component?

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Interesting 1-2 shift delay discovery | 400E / E420 Discussions

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Hi All. Having two issues with my 94 Limited. First issue is it does not upshift at correct revs, ends up revving quite high and I have to trick the transmission by blipping the throttle and it sometimes changes then. This isn't a major issue for me. The real problem is when I accelerate...

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[Sdemon]

Many thanks for your replies

yes I have read most of those articles but I could not understand it was a definitive click you felt. The first article you posted had a few things I needed to look into and the video of the lockdown clearly shows what I should have but do not. Thank you for clarifying this.

With regards to the vehicle it’s the 129.067 version I believe

I definitely do not have a click. So something I need to look into. As read could be the switch, the Solenoid,cable

This thud, is that normal? It happens when I slow down I assume in a higher gear, then when I engage in acceleration it thuds. I’m thinking that that is shifting down into a lower gear?

Apologies if I have repeated a question before I’m just starting out learning about this vehicle

many thanks

 

[gsxr]

I definitely do not have a click. So something I need to look into. As read could be the switch,

No click? Check the switch. They can fail. It takes a LOT of pressure with your fingers (if you remove it). Also make sure a floor mat isn't restricting pedal movement when you push with your foot.

This thud, is that normal? It happens when I slow down I assume in a higher gear, then when I engage in acceleration it thuds. I’m thinking that that is shifting down into a lower gear?

I think what you are describing is a slip / flare during a downshift. For example slowing from 80kph down to 30kph, to make a turn, then accelerating... the trans will drop from 4th gear to 2nd and may clunk/thud. This isn't normal but it's not easy to fix either. There's a TSB in the transmission troubleshooting manual. It would help if you had a video of the exact problem though; I'm not sure if this is what you are describing or not.

 

[Sdemon]

Hi there

I will have to check the switch. Just to check though, does my 1992 r129 have such a switch?

that does sound like what you are describing. Unfortunately when you want to video tape these thing they never occur. Is this anything related to the Bowden cable and positions or is this an internal tranny issue now

TSB in the trouble shooting manual? Sorry what/where is that?
Many thanks

 

[TimL]

1) Yes
2) When the kickdown occurs, the RPM's should increase substantially (i.e., from 2krpm to 4k, approximately)
3) You should feel a distinct "click" when the switch is engaed below the pedal. You can test & listen for this with the engine off.

BTW, what year 500SL do you have (129.066 or .067)?

From a stop, acceleration should look like this, approximately (E500E shown in video).

Woah, Dave, that is damn quick to 60...I guess now I‘ll have to worry about the pace of my car

 

[gsxr]

TSB in the trouble shooting manual? Sorry what/where is that?

Technical Service Bulletin, documents published by Mercedes to dealerships about specific issues. There is a collection of these for the 722 mechanical transmissions but AFAIK it's never been published or commonly available to the public. I remember this particular scenario because I have one particular transmission (a Schmid rebuild with <5kmi on it) that has the exact symptom I described above. Really annoying, I pulled it out of the car and it's been sitting on the workbench collecting dust.

Woah, Dave, that is damn quick to 60...I guess now I‘ll have to worry about the pace of my car

Most well-running 036's should do the same, or close to it. If you think yours isn't quite up to snuff, put a stopwatch to it on a flat road, starting in 1st, no passengers or cargo, etc. Even better if you can get some times to higher speeds although that may not be possible in some areas.

 

[Sdemon]

Thanks for your help. I’ll start with the switch and see what happens.
The only extra piece of information is that when I had work done on it the mechanic said that the only fault code was from the throttle body which he reset. The wiring has been changed along with the wiring harness.

Ill update you when things evolve.

if you do find out what the issue is please let me know



many thanks again

 

[Efraim]

No click? Check the switch. They can fail. It takes a LOT of pressure with your fingers (if you remove it). Also make sure a floor mat isn't restricting pedal movement when you push with your foot.

This is also my hint and true "low hanging fruit". The button like switch should be accessible also by hand.