Author Topic: Manual to automatic using W123 automatic gear box  (Read 1861 times)

chuen teck

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Manual to automatic using W123 automatic gear box
« on: February 12, 2024, 22:23:26 »
Hi everyone,
I was told by a mechanic in Malaysia that one could convert a manual W113 to automatic by using the automatic gear box of a W123 quite easily. Any one has experience here?
Thanks

lpeterssen

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Re: Manual to automatic using W123 automatic gear box
« Reply #1 on: May 02, 2024, 11:03:15 »
Dear Chuen

I think that the mechanic that told you that, did not consider one electrical control issue which is important on the pagodas.  That is the fact that automatic transmissions for mechanical fuel injected cars, provided some signals to the fuel injection system to increase iddle speed if the engine was about to quit. (stalling).

There is a connection strip terminal with 4 wires on the automatic transmissions, designed to work with Mercedes mechanical fuel injected cars control logic.  That connection block has the following signals, which for sure were not present on a w123 since the control approach was absolutely different:

1. Iddle switch positive signal. Active whenever throttle butterfly at intake manifold is clossed
2. Low transmission oil pressure, trigger signal for the iddle increase selenoid (negative signal)
3. Kickdown signal (for sure this one should be present on a w123)
4. Ground

I work a lot on wiring harnesses, and love also to produce practical solutions for classical Mercedes Benz owners.

I have been asked once by a customer to fabricate a wiring harness to convert his Manual transmission w113 to automatic as per original design. 

Since that request, I have made that product standard on my listing on www.wiredoktor.com web page.

See here the link to that:

https://wiredoktor.com/products/mb-w113-manual-to-automatic-harness-conversion-kit

Best regards
Eng.Leonardo Peterssen
Classic car owner and CEO for www.wiredoktor.com
« Last Edit: May 03, 2024, 10:07:44 by lpeterssen »

roberhofer

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Re: Manual to automatic using W123 automatic gear box
« Reply #2 on: May 04, 2024, 07:12:33 »
Someone seems to have been able to make the 722.6 5G Tronic work:
https://youtube.com/shorts/0Us5Kj2A0K4?si=CSJBcw1xwEy4Fx19

lpeterssen

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Re: Manual to automatic using W123 automatic gear box
« Reply #3 on: May 04, 2024, 10:34:23 »
Someone seems to have been able to make the 722.6 5G Tronic work:
https://youtube.com/shorts/0Us5Kj2A0K4?si=CSJBcw1xwEy4Fx19

Yes there is no doubt that you can make a different MB automatic transmission to work on a W113, the point is that you will loose part of the control mechanism that the original w113 transmission has over the engine RPM compensation at IDDLE.

Modern transmissions do not provide those signals needed to fine tune the working of a mechanically fuel injected engine, because modern transmissions are thought for modern cars which have a totally different control approach.

That is just what I am saying.

Best regards
L.Peterssen