What is the main function of overload switch ?
I removed the switch and i have no different in the gear ( every thing normal
) ?
I removed the switch and i have no different in the gear ( every thing normal
) ?
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Transmission overload protection switch ?
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Re: overload switch ?
That's not surprising, as that switch actually has no function the vast majority of the time. The switch function becomes significant during full throttle up shifts and down shifts into second gear.
To limit the load applied to the number one transmission band and provide smoothness, the ignition control unit applies a deep but brief timing retard during extremely high load 1-2 up shifts and 3-2 downshifts. This results in an engine torque reduction that results in a faster and smoother shift into second gear, along with less thermal and mechanical load on the number one brake band. This timing retard is applied just as the ignition control unit "senses" the RPM change as the shift commences. The timing retard is removed the instant that pressure is built up inside that switch.
Note that during these two shifts, the number one brake band is restraining the movement of the number one clutch drum. The switch responds to pressure build up in the spring-loaded retaining member of the transmission band. That build up of pressure occurs just as the rotation of the number one clutch drum ceases. In that manner, the switch signals to the ignition control unit that the shift into second gear has fully completed, and in response to that signal, the ignition control unit releases the timing retard.
Contrary to some peoples imaginings, eliminating the switch from the circuit does not result in a performance gain during those shifts. Note that the switch does not produce the timing retard, it only limits the period of the timing retard. The ignition controller ALWAYS provides the timing retard during those shift points if they occur at an extremely high load (essentially, full throttle). Without the change in state of the switch being available as a signal, the ignition control unit simply applies an extremely long period of timing retard lasting well past any possible time required for the mechanical shift event to take place. Note also that jumping the switch to "lie" to the control unit produces the same effect. The logic of the control unit recognizes implausible states and reacts accordingly, again with a long duration timing retard...
What is the main function of overload switch ?
I removed the switch and i have no different in the gear ( every thing normal
That's not surprising, as that switch actually has no function the vast majority of the time. The switch function becomes significant during full throttle up shifts and down shifts into second gear.
To limit the load applied to the number one transmission band and provide smoothness, the ignition control unit applies a deep but brief timing retard during extremely high load 1-2 up shifts and 3-2 downshifts. This results in an engine torque reduction that results in a faster and smoother shift into second gear, along with less thermal and mechanical load on the number one brake band. This timing retard is applied just as the ignition control unit "senses" the RPM change as the shift commences. The timing retard is removed the instant that pressure is built up inside that switch.
Note that during these two shifts, the number one brake band is restraining the movement of the number one clutch drum. The switch responds to pressure build up in the spring-loaded retaining member of the transmission band. That build up of pressure occurs just as the rotation of the number one clutch drum ceases. In that manner, the switch signals to the ignition control unit that the shift into second gear has fully completed, and in response to that signal, the ignition control unit releases the timing retard.
Contrary to some peoples imaginings, eliminating the switch from the circuit does not result in a performance gain during those shifts. Note that the switch does not produce the timing retard, it only limits the period of the timing retard. The ignition controller ALWAYS provides the timing retard during those shift points if they occur at an extremely high load (essentially, full throttle). Without the change in state of the switch being available as a signal, the ignition control unit simply applies an extremely long period of timing retard lasting well past any possible time required for the mechanical shift event to take place. Note also that jumping the switch to "lie" to the control unit produces the same effect. The logic of the control unit recognizes implausible states and reacts accordingly, again with a long duration timing retard...
Re: overload switch ?
The most common cause of harsh 1-2 upshifts is excessive clearance on brake band number one. The next most common cause, though exceedingly rare is a broken band two timing accumulator spring in the valve body, and or previous tampering with the valve body...
The most common cause of harsh 1-2 upshifts is excessive clearance on brake band number one. The next most common cause, though exceedingly rare is a broken band two timing accumulator spring in the valve body, and or previous tampering with the valve body...
Re: overload switch ?
If the switch is disconnected or not working properly, the full-throttle shifts are affected (delay / hang). There is no change at part throttle, but the WOT shifts will not be correct until you fix it. The switch is cheap and easy to replace, if it's defective, just change it.
Anyone who doesn't believe me - go unplug the switch and then do a bunch of WOT runs, pay attention to how the upshift occurs. Now reconnect the switch and repeat. Trust me, the switch MUST be functioning for optimal performance.
M104 FSM shown below, M119 is essentially the same:
If the switch is disconnected or not working properly, the full-throttle shifts are affected (delay / hang). There is no change at part throttle, but the WOT shifts will not be correct until you fix it. The switch is cheap and easy to replace, if it's defective, just change it.
Anyone who doesn't believe me - go unplug the switch and then do a bunch of WOT runs, pay attention to how the upshift occurs. Now reconnect the switch and repeat. Trust me, the switch MUST be functioning for optimal performance.
M104 FSM shown below, M119 is essentially the same:
Re: overload switch ?
Thanks Dave. Since you are usually the one that gets the heat on issues like this, I wanted to point out another "literature error".
Interestingly enough, that particular functional description always angered me because it is incorrect. That switch is not connected to the working pressure side of the hydraulic circuit, nor even to the operating pressure side of the circuit for the B1 piston. It is hydraulically connected to the reaction valve circuit. The reaction valve is inside that spring-loaded stationary retainer for the B1 band. The nipple of that valve actually enters the reaction valve portion of the band retainer. The interesting thing about this set up is that just as the rotating drum that the band is grabbing becomes stationary, the large torque reversal produced jams the reaction valve closed, which results in the immediate buildup of pressure inside of it, forming an elegant hydraulic "signal" that the shift process has completed. That sudden pressure spike is what closes the switch. Other valves in the valve body are also diplaced by that pressure, and they then apply the full available working pressure to the band piston. This is how the valve body modulates the smoothness of the downshift process. I just threw that in there to point out yet another example of how so often there is a lot more going on than the often wildly oversimplified functional descriptions lead one to believe...
If the switch is disconnected or not working properly, the full-throttle shifts are affected (delay / hang). There is no change at part throttle, but the WOT shifts will not be correct until you fix it. The switch is cheap and easy to replace, if it's defective, just change it.
Anyone who doesn't believe me - go unplug the switch and then do a bunch of WOT runs, pay attention to how the upshift occurs. Now reconnect the switch and repeat. Trust me, the switch MUST be functioning for optimal performance.
M104 FSM shown below, M119 is essentially the same:
Thanks Dave. Since you are usually the one that gets the heat on issues like this, I wanted to point out another "literature error".
Interestingly enough, that particular functional description always angered me because it is incorrect. That switch is not connected to the working pressure side of the hydraulic circuit, nor even to the operating pressure side of the circuit for the B1 piston. It is hydraulically connected to the reaction valve circuit. The reaction valve is inside that spring-loaded stationary retainer for the B1 band. The nipple of that valve actually enters the reaction valve portion of the band retainer. The interesting thing about this set up is that just as the rotating drum that the band is grabbing becomes stationary, the large torque reversal produced jams the reaction valve closed, which results in the immediate buildup of pressure inside of it, forming an elegant hydraulic "signal" that the shift process has completed. That sudden pressure spike is what closes the switch. Other valves in the valve body are also diplaced by that pressure, and they then apply the full available working pressure to the band piston. This is how the valve body modulates the smoothness of the downshift process. I just threw that in there to point out yet another example of how so often there is a lot more going on than the often wildly oversimplified functional descriptions lead one to believe...
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Can somebody explain to me what is the part that is located underneath the overload protection switch? In the picture the number is 232. Is connected to the wire. In my 500E noticed that part but not in others 500E
Yes, but I'll have to do it later...
Your 500E transmission should look like the photo below. There should not be anything on your transmission that isn't on everyone else's 500E transmission.
EDIT: Very early build, Euro-spec 036 transmissions will have item #232. But no USA-spec car should have this.
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Interesting. The 129.066 has a different transmission, so it could have different external components. I've never heard of any 124.036 (or .034) having the item specified in post #7...
Can somebody explain to me what is the part that is located underneath the overload protection switch? In the picture the number is 232. Is connected to the wire. In my 500E noticed that part but not in others 500E
Kamylek, That is indeed the bracket and related piping for a cold upshift delay solenoid for rapid catalyst heating as Clark stated up above.
It has created a minor mystery here because no USA version 124.036 vehicle uses that particular arrangement. The EPC does show it as relevant for 722.365 transmissions in catalyst equipped vehicles in the ECE up to transmission end number 3559497.
If you wouldn't mind, please supply the chassis and transmission end numbers of your vehicle. If you don't want to post them, send a PM if you like that better. I'd like to look these items up with specific reference numbers. We yanks may be getting some additional education here...
Thanks!
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I have the same part in my carCan somebody explain to me what is the part that is located underneath the overload protection switch? In the picture the number is 232. Is connected to the wire. In my 500E noticed that part but not in others 500E
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Additional forum resources on the topic, if needed:
Additional / supplemental HOW-TO:
HOW-TO: Transmission Overload Protection Switch Removal | "HOW-TO" Tutorial Articles
MODERATOR'S NOTE: There is a supplemental HOW-TO guide for this job, located here. It is advised to read both the original and supplemental HOW-TO guides to best understand and achieve this job. Today, I attempted to replace the transmission overload protection switch, located on the left...
www.500eboard.co
Additional / supplemental HOW-TO:
HOW-TO: Transmission Overload Protection Switch Removal | "HOW-TO" Tutorial Articles
MODERATOR'S NOTE: There is a supplemental HOW-TO guide for this job, located here. It is advised to read both the original and supplemental HOW-TO guides to best understand and achieve this job. Today, I attempted to replace the transmission overload protection switch, located on the left...
www.500eboard.co
@Klink Do you know how the EZL knows if the the shift is 1-2 or 3-2 as opposed to 3-4 or 4-3? The EZL sees the RPM change, and pulls timing until it sees second gear fully engage. Presumably it should not be doing the same when shifting into 3rd since there is no overload switch for 3rd gear, so I'm wondering how the EZL knows the shift is into 2nd, and whether it will also pull timing in 3rd. My 400E is misbehaving on 4-3 shifts and throwing an overload switch code. I've replaced the switch and verified it is indeed working in 2nd as it should. Just trying to understand the function of the overload switch a little better so I can try to solve this.Re: overload switch ?
That's not surprising, as that switch actually has no function the vast majority of the time. The switch function becomes significant during full throttle up shifts and down shifts into second gear.
To limit the load applied to the number one transmission band and provide smoothness, the ignition control unit applies a deep but brief timing retard during extremely high load 1-2 up shifts and 3-2 downshifts. This results in an engine torque reduction that results in a faster and smoother shift into second gear, along with less thermal and mechanical load on the number one brake band. This timing retard is applied just as the ignition control unit "senses" the RPM change as the shift commences. The timing retard is removed the instant that pressure is built up inside that switch.
Note that during these two shifts, the number one brake band is restraining the movement of the number one clutch drum. The switch responds to pressure build up in the spring-loaded retaining member of the transmission band. That build up of pressure occurs just as the rotation of the number one clutch drum ceases. In that manner, the switch signals to the ignition control unit that the shift into second gear has fully completed, and in response to that signal, the ignition control unit releases the timing retard.
Contrary to some peoples imaginings, eliminating the switch from the circuit does not result in a performance gain during those shifts. Note that the switch does not produce the timing retard, it only limits the period of the timing retard. The ignition controller ALWAYS provides the timing retard during those shift points if they occur at an extremely high load (essentially, full throttle). Without the change in state of the switch being available as a signal, the ignition control unit simply applies an extremely long period of timing retard lasting well past any possible time required for the mechanical shift event to take place. Note also that jumping the switch to "lie" to the control unit produces the same effect. The logic of the control unit recognizes implausible states and reacts accordingly, again with a long duration timing retard...
I thought about this before, and I may even have worked it out once and have simply forgotten, But here's what I do know along with the additional caveats I will mention as I go.
I don't know exactly how it "knows" but I know that it does. If I had more time I would research it further right now, but that's not possible for the time being.
I believe, though I'm not absolutely certain of the following:
In addition to the pressure activated switch in the number one transmission band thrust body/reaction valve which provides real time confirmation of the applied and unapplied states of the number one brake band, the EZL receives information over the chassis CAN network regarding the vehicle speed and the shift lever position. And it obviously knows the real time engine RPM because it is the control unit that calculates and broadcasts engine speed to other "interested" control units on the chassis CAN and the instrumentation. I do know that with the information it receives, it CALCULATES the actual gear that the transmission is in at any given instant. As you have already worked out, it does not receive literal and/or perfect Information regarding the actual physical status of the applied shift elements. Regarding your situation, the EZL is not likely to be having a negative influence on shifts not involving the application or release of the number one transmission band IF there are no hydraulic or mechanical faults with the B1 related components. I may return to this later, because I have some thoughts behind the "IF"
For what it's worth, the V12 cars using the 722.3 transmission do employ similar ignition retard smoothness/protection strategies on other shifts, and there is at least one additional pressure activated switch like that on B1 that supply the additional information required to facilitate the function. I don't remember right now which hydraulic pressures the additional switch or switches monitor, but I think it's the applied position of band number two via the B2 thrust body/reaction valve exactly as it's done on B1.
I don't know exactly how it "knows" but I know that it does. If I had more time I would research it further right now, but that's not possible for the time being.
I believe, though I'm not absolutely certain of the following:
In addition to the pressure activated switch in the number one transmission band thrust body/reaction valve which provides real time confirmation of the applied and unapplied states of the number one brake band, the EZL receives information over the chassis CAN network regarding the vehicle speed and the shift lever position. And it obviously knows the real time engine RPM because it is the control unit that calculates and broadcasts engine speed to other "interested" control units on the chassis CAN and the instrumentation. I do know that with the information it receives, it CALCULATES the actual gear that the transmission is in at any given instant. As you have already worked out, it does not receive literal and/or perfect Information regarding the actual physical status of the applied shift elements. Regarding your situation, the EZL is not likely to be having a negative influence on shifts not involving the application or release of the number one transmission band IF there are no hydraulic or mechanical faults with the B1 related components. I may return to this later, because I have some thoughts behind the "IF"
For what it's worth, the V12 cars using the 722.3 transmission do employ similar ignition retard smoothness/protection strategies on other shifts, and there is at least one additional pressure activated switch like that on B1 that supply the additional information required to facilitate the function. I don't remember right now which hydraulic pressures the additional switch or switches monitor, but I think it's the applied position of band number two via the B2 thrust body/reaction valve exactly as it's done on B1.
