1993 300d manual trans swap - PeachParts Mercedes-Benz Forum

Watson52 · #1 12-17-2015, 02:46 PM

I am in the process of installing what I believe is a w201 5 speed manual trans in a 1993 300d. Can anyone tell me what the two small cables attached to the automatic shifter are for?

Thanks

jay_bob · #2 12-17-2015, 02:54 PM

You should have the following:

- a vacuum line, leading up to the "blue flying saucer" in the engine bay. You will be able to greatly simplify the vacuum system on a 124 after this.

- an electrical line, with the neutral safety and reverse light leads. This goes to a switch in the side of the auto transmission. Manuals do not have an NSS and the reverse light is handled in the shifter mechanism.

- speedometer cable, this stays.

- two fluid cooling lines, these can go.

Watson52 · #3 12-17-2015, 03:14 PM

Wow that was fast! I am asking about the automatic shifter itself. It has a lever that attaches to the rod that goes to the automatic transmission and two cables that attach to the shifter on the right side. I am curious about the two cables. What are they?

Thanks for the response!

vstech · #4 12-17-2015, 04:57 PM

They are the key and brake pedal interlock, you should be able to thread the key interlock into a nut to engage the key...

Or pull the shifter, and ignition assembly out, and send it to me, and I can swap it for a non interlock set.

Watson52 · #5 12-17-2015, 09:42 PM

Where exactly do I thread a nut?

Thanks for the response

sixto · #6 12-17-2015, 10:51 PM

As John says it's the interlock so you can only remove the key with the shift lever in P and release the lever from P with the key in the switch and your foot on the brake (thanks, Audi). I don't know what the key switch cable looks like but I imagine John means you can jam it with a nut so you can remove the key absent a compatible AT shifter mechanism.

Sixto
83 300SD

jay_bob · #7 12-18-2015, 07:55 AM

Oh sorry I did not read the first post completely. I thought you meant the transmission itself.

There are two Bowden cables from the auto shifter back into the cockpit.
One goes to the key switch and the other to the brake pedal. They work together to ensure you cannot take the car out of park without your foot on the brake and you can't remove the key unless it's in park.

The brake pedal cable can be ignored if you don't want to mess with removing it. There is a group of us older 124/201 owners that wish to retrofit these interlocks into the pre 1990 models so you may have good luck selling or swapping the interlock mechanisms for non interlock.

You will either need to swap key switch mechanisms or fasten the free end of the cable from the key switch at the shifter end so that the switch always thinks it is ok to remove the key.

I actually found the pedal and shifter from a gas 124 in the yard a while back. That and the passenger air bag. I plan to work with my son to install these over the holidays. I do not have the key switch from the donor because it was a gas so it does not have the vacuum shut off mechanism.

euroamg · #8 12-18-2015, 12:28 PM

Looking forward to this swap. I have a 300d that i was planning to do a 5 speed swap too sometime. I have the complete 5 speed car with me..

Watson52 · #9 12-18-2015, 05:12 PM

Thanks a lot! Vacuum cutoff?

jay_bob · #10 12-19-2015, 08:23 AM

On the older MB Diesel cars (123/124/126/201 and older) the engine is shut off by stopping the fuel. On the mechanically controlled engines you have a vacuum valve in the switch assembly. This directs vacuum to a diaphragm on the injection pump. This diaphragm pulls a lever that drives the rack to the "zero fuel" position.

The 140 and 210 still had an IDI engine, but had computer controls, so they used a vacuum solenoid on the 140 to the IP actuator, and an electric fuel valve on the 210.

Later models with CDI are shut down by the computer ceasing the commands to inject fuel.

Totally different than a gas car, where removing the electricity from the ignition stops the engine. Theoretically you could still drive your 124 with a completely dysfunctional electrical system once you got it glowed and started.

If you haven't already, I would go to startekinfo.com and locate the MB Workshop Resources link and then find the 124 Service Info. MB put the entire factory manual set online for this car and it is invaluable.

tjts1 · #11 12-19-2015, 10:19 AM

On my 87 5spd swap I was able to eliminate 90% of the vacuum hoses under the hood. Only thing left is the shut off valve and ALDA. This might be a good time to convert your vacuum waste gate to a normal pressure waste gate.

Watson52 · #12 12-19-2015, 01:27 PM

Thanks for all the great suggestions. As for the shifter cables, if the key goes in and out I shouldn't have a problem? With the wire to the clutch master, I am not concerned too much about starting in gear, but I do want the cruise to work. The switch is normally closed. Does anyone have a diagram of how it and the brake switch should be wired for the cruise to function properly?

Thanks for all the help

gatorblue92 · #13 12-20-2015, 06:35 AM

Quote:

Originally Posted by Watson52

Thanks for all the great suggestions. As for the shifter cables, if the key goes in and out I shouldn't have a problem? With the wire to the clutch master, I am not concerned too much about starting in gear, but I do want the cruise to work. The switch is normally closed. Does anyone have a diagram of how it and the brake switch should be wired for the cruise to function properly?

Thanks for all the help

I didn't do anything with the wires for my 5 speed swap in my 91 300TE and the cruise functions properly. I hardly ever use it since there is usually a lot of traffic in my area but one disadvantage so my setup is if the clutch pedal was depressed for some reason the engine could redline. Applying the brakes has the normal function of stopping the cruise.

One idea I had but never followed through on was hooking up the neutral safety switch leads to the clutch pedal switch so I would have a starter interlock. Right now you can start the car while its in gear.

vstech · #14 12-20-2015, 09:04 AM

Quote:

Originally Posted by Watson52

Thanks for all the great suggestions. As for the shifter cables, if the key goes in and out I shouldn't have a problem? With the wire to the clutch master, I am not concerned too much about starting in gear, but I do want the cruise to work. The switch is normally closed. Does anyone have a diagram of how it and the brake switch should be wired for the cruise to function properly?

Thanks for all the help

The cable has a button on the end that needs to be pushed in to release the key.
You could weld a nut to a chunk of steel and thread it onto the end of the cable or, as I said... I would LOVE to swap one of my assemblies for yours!

I have one set already, but another would be great.