Transmission Modulator Adjustment Cap?` - PeachParts Mercedes-Benz Forum

JamesDean · #1 03-30-2011, 01:55 PM

Hey everyone I was going to adjust the modulator on my one 300SD and the cap looks strange. Im used to the rubber cab like my other SD has...

Whats the deal here? The black stuff all over is just over spray from when I undercoated stuff.

compress ignite · #2 03-30-2011, 02:29 PM

Congratulations !
"You've been Screwed,by a Previous: Owner or Wrench Turner."

That's the "One Time Only Use" CAP
(You're supposed to "Adjust the Modulator Correctly" and then install the cap)
(CAP provides a miniscule amount of adjustment)
Rumor has it,removing the CAP destroys it.

sjh · #3 03-30-2011, 03:20 PM

I just put a new modulator on my '90 300D 2 weeks ago. It's the same unit as you have. I installed the unit, adjusted the setting with the metal "T" and placed the cap over it.

If I need to adjust the setting in the future I remove the cap, adjust the "T" and replace the cap.

Perhaps there is something else That I am missing but my experience to date is that these units work fine.

josha37 · #4 03-30-2011, 03:26 PM

thats the one i have, there is a spring clip that holds it on, find it squeeze it and remove. under it is a metal t that you pull out and then turn to adjust. Works great done mine a few times to get it right.

JamesDean · #5 03-31-2011, 02:32 AM

Hm I cant see a spring clip from the picture. It might be buried. This poor trans shifts hard as heck. The modulator holds vacuum I checked with the MityVac.

Tomorrow, if it warms up at all, I'll pop the plastic cap thing off and see what I can do. If it breaks I'll just replace it with the rubber-cap style ones, its like $30 or something.

Is that plastic cap like original stuff and the rubber ones newer or? vice-versa?

layback40 · #6 03-31-2011, 07:14 AM

James,
The rubber ones are the original old ones. I have never seen these new plastic ones. Even my w124 has the rubber one. You may be lucky if it is damaged during the removal & be able to use a rubber one from an old trans.
Good luck & remember not to put too much force on the plastic & break it !!!

JamesDean · #7 03-31-2011, 02:39 PM

Well, plastic is broken. I mostly expected that however.

I can still buy the rubber cap type ones. I've seen them listed on a few parts websites for $30-$35.

Looks like I can replace it without having to drain anything, which is good. I just filled it. lol.

Looks like a pretty easy install. Two bolts..

compress ignite · #8 03-31-2011, 03:07 PM

For "Official" directions to the "New" Modulator.

http://www.peachparts.com/shopforum/showthread.php?t=290589&highlight=modulator

AND,YES if you have access to the Old Style Modulator,
It'll save you angst in the future.

jmbeam · #9 10-16-2011, 12:10 PM

How exactly to these caps come off without breaking them? If I connect a vac gauge to the modulator and it holds vacuum then its ok?

Biodiesel300TD · #10 10-16-2011, 12:19 PM

Quote:

Originally Posted by jmbeam

How exactly to these caps come off without breaking them? If I connect a vac gauge to the modulator and it holds vacuum then its ok?

With a mity vac attached you should be able to pull vac up to about 15"Hg and then it will bleed off over 30 seconds or so. If you can't get any vac pulled then the modulator is bad.

jmbeam · #11 10-16-2011, 12:23 PM

JUst discovered that I have a one time modulator. If I need to adjust further I will need to purchase a new one.The cap is destoyed if it is taken off, nice.... Its a ONE TIME PART!

tyl604 · #12 10-16-2011, 02:11 PM

I do not quite understand. The "one time" gizmo is supposed to be the white plastic cap - as opposed to the old black rubber cap which can be removed and replaced. Never heard of a one time modulator. However I have removed my new white plastic cap and readjusted my modulator twice - and this is after the mechanic who installed the used tranny removed it twice and adjusted the modulator earlier. So I know for a fact that the white one can be rmoved and reused. I just pried it off gently with a flathead screwdriver, turned the adjuster a little and pressed it back on.

Why do you think the modulator is bad? The tranny is designed to upshift fine with zero vac and needs vac only to downshift. What are your symptoms?

jmbeam · #13 10-16-2011, 02:51 PM

WHat part of the modulator came off? I tried but it seemed like I was going to damage it trying to remove it. Since I dont have a replacement I stopped trying.

tyl604 · #14 10-16-2011, 05:44 PM

I removed the white plastic cap. It has an opening on the side to adjust the modulator without removing it. Just pried it off and popped it back on after turning the adjuster.

compress ignite · #15 10-17-2011, 02:03 AM

The little white plastic caps (with the protruding lever) are supposed to be
"One time use only".

If "Gently" prying one off works,Hooray.

Even if you "Bugger " one up R+Ring it a New White Plastico Cap is only a couple of Dollars.
There's a separate part number for it in the EPC. [126 987 07 45]