Transmission Modulator

[johan01]

Just had an episode with my 280S. The ATF is being sucked into the engine and coming out as a big plume of whilte smoke through what I believe is the modulator in the tranny.

Has anyone tackled this before? What needs to be done and how difficult is it to change the modulator?

Thanks in advance,

[cth350]

John, the task is "trivial".

1. Find a replacement.
2. follow instructions from the manual.

I can help you with #2 easily enough. Good luck with #1.

Drop me an email tonight (NYC time).

-CTH

[stevebfl]

If its a 69 or earlier the modulator isn't a single component and all you need is the diaphram part# 112 270 00 79 which is pretty cheap at $25.50 MB list.

Item # 140

[johan01]

My car is a '68 and the transmission modulator sure looks like the one in the attached picture.

Unfortunately, the modulator I got was the wrong kind -- its cylindrical and has two fittings at both ends. I had it returned and the shop is looking for the correct one.

I gave them the part # for the diaphram -- it should help. Thanks.

Any chance you have the part number for a the modulator assembly?

Thanks in advance,

[stevebfl]

There is no assembly unless of course you mean the whole transmission. The disphram is basically as simple to change as component modulators.

[johan01]

There is no assembly unless of course you mean the whole transmission.

That's what I thought. Its just the local parts guys here can't find the diaphram and they're looking for a whole modulator assembly -- just in case...

Thanks

[stevebfl]

The number I gave will work at any MB dealer. Its universal, worldwide.

[johan01]

Just to wrap this up. I was able to get the rubber diaphram from the US and it took a while to get here.

With the car raised on jackstands, I crawled under the car and removed the vacuum modulator. I had to remove the vacuum pipe with 17mm wrench, then removed the three 8mm hex bolts.

Clearance was tight since the exhaust is right where I don't need them. The last of the 8mm bolt was very tricky to remove.

Once removed from the transmission, I pried the old rubber diaphram out and intalled the new diaphram. Put the spring and cover back in, tightened the bolts, put the vacuum tube back.

Poured about a liter of ATF, started up and took it for a drive. It feels refreshing to be back behind the wheel of the W108. Had her grounded for almost a month.

The ATF induced smoke eventually went away after a few minutes drive -- ATF was probably still in the vacuum pipe and took a few miles before it all got injested.

Shifting behavior is the same as before the diaphram blew -- so no magic there. But at least the car's not smoking and is driveable again.

The 3-way electric solenoid in the transmission is not working, so that's my next target.

Thanks for all your help,