W114 73 280 transmission replacement - PeachParts Mercedes-Benz Forum

paulelli8 · #1 05-17-2017, 05:59 PM

Hi all,

I am in need of your expertise. I have a 1973 280 with a bad trans and found an exact year/model match donor at a salvage yard. I purchased the trans from the donor to replace mine, but now we've got it ready to go in and I have a very important question my mechanic could not answer.

I've attached two photos. The first is my original transmission. You can see there is a electrical switch in the forefront of the picture with some type of hydraulic function.
[INDENT][INDENT]

W114 73 280 transmission replacement-img_1055.jpg.jpg

The second is from the donor and has no such switch. The big question is what does this do and is it critical to the performance of the transmission?? Or does it serve a secondary function and I can go ahead with the swap.

[INDENT][INDENT]

W114 73 280 transmission replacement-img_1056.jpg.jpg

Frank Reiner · #2 05-17-2017, 07:10 PM

Quote:

Originally Posted by paulelli8

Hi all,

I am in need of your expertise. I have a 1973 280 with a bad trans and found an exact year/model match donor at a salvage yard. I purchased the trans from the donor to replace mine, but now we've got it ready to go in and I have a very important question my mechanic could not answer.

I've attached two photos. The first is my original transmission. You can see there is a electrical switch in the forefront of the picture with some type of hydraulic function.[INDENT][INDENT]Attachment 142272

The second is from the donor and has no such switch. The big question is what does this do and is it critical to the performance of the transmission?? Or does it serve a secondary function and I can go ahead with the swap.[INDENT][INDENT]Attachment 142273

That switch serves to cancel the ignition retard in fourth gear. When the trans goes into 4th, pressure at that port is applied to the switch, and a switchover valve in the emission controls removes the retard vacuum from the distributor. By permanently removing the vacuum connection to the distributor the same result is obtained; the retard only causes the engine to run hot in the first three gears.

What are the numbers stamped into the case on the right side, just above the oil pan? 722.xxx - xxxxxx

ScooterABC · #3 05-17-2017, 07:42 PM

Do you have any reason to think that the junkyard transmission is any better than the one in your car?

paulelli8 · #4 05-17-2017, 08:03 PM

Scooter, I understand why you would pose that question. Short of a rebuild this was a much cheaper alternative. Of course I don't know for sure, but given the overall value of the car I didn't see spending more worth it for me. I can say I highly doubt it will be worse than the one I have, having driven with it for a while.

Frank, thank you for this info. So I'm hearing its not critical. While we're at it do you know what the second switch does on my original transmission (further back, middle center of the photo)? Looks like a USB port for my phone.

Otherwise I can post the numbers tomorrow morning. Can you say why it wouldn't have this switch? Just a previous iteration or based on something else model specific?

ScooterABC · #5 05-17-2017, 08:10 PM

I guess I'm thinking the labor to swap the transmissions is significant. I've never done it with an autobox so I don't know. Friends who have said that it's not easy.

For my wagon I bit the bullet and had it rebuilt at Sun Valley Mercedes, but that was for a car that I expected to be driven for a long time, and probably has more residual value than a 280.

I hope your transmission swap works!

Frank Reiner · #6 05-17-2017, 08:51 PM

Quote:

Originally Posted by paulelli8

Scooter, I understand why you would pose that question. Short of a rebuild this was a much cheaper alternative. Of course I don't know for sure, but given the overall value of the car I didn't see spending more worth it for me. I can say I highly doubt it will be worse than the one I have, having driven with it for a while.

Frank, thank you for this info. So I'm hearing its not critical. While we're at it do you know what the second switch does on my original transmission (further back, middle center of the photo)? Looks like a USB port for my phone.

Otherwise I can post the numbers tomorrow morning. Can you say why it wouldn't have this switch? Just a previous iteration or based on something else model specific?

The "second switch" is not a switch at all; it is the kickdown solenoid.
And it is located further forward on the trans. The emissions switch is toward the back of the trans.

Why the emissions switch is not on the second trans may be answered by the model numbers.

paulelli8 · #7 05-18-2017, 03:26 PM

Thanks Frank, that makes sense. Here are photos of the numbers stamped on both transmissions. The first is my original...

114 270 1501000499

W114 73 280 transmission replacement-img_1062.jpg.jpg

And the second is from the donor car....

114 270 1601003820

W114 73 280 transmission replacement-img_1061.jpg.jpg

Frank Reiner · #8 05-18-2017, 04:24 PM

Quote:

Originally Posted by paulelli8

Thanks Frank, that makes sense. Here are photos of the numbers stamped on both transmissions. The first is my original...

114 270 1501000499
Attachment 142285

And the second is from the donor car....

114 270 1601003820
Attachment 142284

Your original trans is a 722.200
The replacement is likely also a 722.2; can you provide a couple of pictures of the replacement taken from the bottom of the trans, and in particular of the bottom of the convertor housing (bell housing).

Some of the transmission part#s of that era defy research, so some external clues must be relied on.