trans just went kaput on my '82 300sd
 

Just lost first gear on my way into work. Slipping under any sort of throttle. Have to go very lightly to get it to move. All other gears ok. Oil is ok. driveline is ok. trans is kaput.

Mine is an '82 300sd w126 with om617. located a used transmision out of an early 80's w123 300d with an om617. Runs and drives well. Body rotten. Are there going to be any issues using this transmission?

I searched the forums, too much info. Are there any good threads on transmission R+R? Bowden cable removal etc? anything to watch out for or any special tricks to know that will make my life easier?

The 300D has a mechanical speedo. Make sure its from a 300D turbo (722.315) if you buy it.

The car is a turbo 617, but i believe you may be right about the speedo. Can it be converted? The trans is free, so the price is right. Speed is intermittant at best right now. I use a GPS speedo app.

If it's free, get it. I'm actually doing this same (W123 --> W126) swap, so I'll let you know how I do... I'm hoping to be done on Monday. Swapping tailshafts is supposed to work.

You may have issues, if that is a 1979 and not an 1980 model it may have the Bowden road only transmission.....which the 1979 linkage is way different then the 1982....so adapting the rod controlled transmission isn't easy...

If this is a 1980 model, it will have a vacuum controlled only transmission, no Bowden rod or cable...

There may also be an issue with one being a turbo and the replacement a non turbo...

I think he said that the donor car is a turbo...

I think it has been reported that the problem with the tail cone swaps is that going from an electronic speedo to mechanical isn't possible because there's no lubrication system for the mechanical cogs - but going the other way is meant to be fine. This only works for the 722.3 transmissions though.

The car is a turbo, and believe it has cruise control. Does this mean it may have both mechanical and electrical speedo tail shaft? I am also certain of has aa bowden cable. Engine bay looks identical to mine, iirc.

No, the cruise control is picked up from the speedometer. I'll get you a pic of my tailshaft and my speedometer so you can see what it look like.

BTW, all turbos came with cruise control.

It is my understanding that only the 1985 300D turbo engined W123 was fitted with a 722.303 and the associated electronic gadets. All of the other turbo OM617 W123s were fitted with the mechanical speedo and the 722.315 transmission.

The trans from my '85 300SD had an electronic speedo, much to my surprise. It has new external seals. When we took the pan down it looked perfect - no shiny bits at all. BTW - a friend has that trans - it's available but I don't know how much he wants for it. If you're interested I'll get back to you on it.

Dan

Are you not interested in replacing the B-2 piston? That is what broke to make first gear not engage. It is much easier to replace than the whole transmission.

I actually replaced my trans at one point with a SD 722.3xx and didn't have a speedo because of the electronic vs. mechanical tail cone.

I agree that the issue is likely B2 piston, I'd look into that first.


Swapping the tailpiece on the trans is doable but a pain. I did it for my SD, bought a transmission from a 1985 300D and swapped the tail. You need a tail piece gasket, rear shaft gasket, and a new yoke nut that you peen into position, you also need the special socket to remove and install the yoke.

X3 on the B2. Why do people worry about speedometers in the age of GPS?

I'm on my mobile, forum search doesnt work well. any good links on the b2 piston? In a pinch, can I just swap it out of the 123 trans to see if it works?