The car has been shifting strange as of late. Hard 1-2 flare 2-3 normal 4. Then it just decided to do whatever it felt like when it wanted to. The latest is a slight hesitation after coming to a complete and then accelerating again. (doesn't sound promising!) Anyway, I am cross eyed over reading the transmission posts and I am looking for some specific answers that should be easy enough.

VCV valve with the vent side blocked will hold vac to 15 but within 12-18 seconds will bleed down to 0. I'm assuming its bad, can it be rebuilt or is replacement the only option?

The modulator bleeds down as well, not as fast, but still does. Someone had mentioned a cap and o-ring. There is no transmission fluid in the line. Where do you get the cap and o-ring? The modulator lists for around $34 I think.

Lastly, for the love of all, how do work on the modulator with the transmission in the car! Man, I had quite a fight with the space just to get the vac hose on it for testing. How do you adjust it? Should I lower the transmission to access it?

I understand the mechanics behind it and I plan on following the appropriate DIY articles, which are plenty and very well written, and they mention the above listed, just not how to do it. I'm hoping that this is a "old vac parts" related issue and not a "rebuilt transmission" issue.

EDIT: Oh! its a 722.315 transmission.

__________________
1980 300TD, SOLD
1984 300TD, 275K
1999 C230 K Black & Tan
2013 C250 Black
1974 CJ5 Red
You might faint from the fight, but you're gonna find it. Every challenge could have paradise behind it. -John Popper-

VCV and modulator seem normal. Your tranmisson oil level ok?

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles

The side panel of the VCV can be removed and the spring can be adjusted:



At idle it must be around 10-12 inHg vacuum. Adjust with a vacuum gauge attached and with a source of vacuum. At full load the vacuum should be 0. The vacuum gauge should respond instantly and directly upon movement of the lever of the VCV.

You can also spray brake cleaner through the VCV, to clean it. Be careful, do this away from the car, as brake cleaner is flammable.

On the 722.315 transmission you can replace the rubber cap. It doesn't have a O ring. Here you can see the modulator with the black rubber cap removed:



You can get a new one at the dealer or make one yourself. The modulator must hold vacuum.

The modulator is adjusted by twisting the key visible in the picture above. You must do this with a pressure gauge attached to the transmission. See here:



and pressure gauge in the car:



At 30 mph without the vacuum line attached it must have a certain pressure.

Thanks guys for the reply. The fluid was a little high when I last checked it, and now I think I may know why. When I pulled the pan to change fluid and filter this is what I found. I immediately went to look in the coolant expansion tank and there is no trans fluid in there, clean and clear.

What I did notice was the three cracks as outlined in the picture. (Btw, how do you upload a photo to the post as opposed to just attaching it?) Now, I didn't have any transmission fluid leaks, and if I did it was so minimal as to me not noticing, but can air be drawn into these cracks and cause the foaming, because they seem to be located in those areas. If so, could that cause the increase volume of fluid level readings and poor shifting? Thoughts?

The fluid is the normal red color and has no bad or burnt smell. It actually looked pretty clean.

The red lettering in the pic says "cracks in rubber gasket"

Attached Thumbnails

 

__________________
1980 300TD, SOLD
1984 300TD, 275K
1999 C230 K Black & Tan
2013 C250 Black
1974 CJ5 Red
You might faint from the fight, but you're gonna find it. Every challenge could have paradise behind it. -John Popper-

I believe the Transmission Vacuum Module is supposed to hold Vacuum and not leak off. Someone else will have to verify that.
If you buy a new Module get a new Transmission Pin as it is said the old ones break off whey you try to remove them.

If you post the pics as the other member did in that post you need to go through a Photo Hosting site. And, when you do that you sort of link the post to that pic.
The disadvantage of that is that if you have to keep the pictures on that Hosted sight forever in in order for them to show up in your post years later.
If you remove your pics from the Host they are gone from your Post.

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84 300D, 82 Volvo 244Gl Diesel

There is a tab at the top of the page called "New Parts Catalog", which also supports this forum. To keep from chasing the problem, resolve the vacuum leaks first. I found the easiest route to take was replacing all of the rubber flex fittings first then going from there. (This will include the modulator cap.) The modulator replacement should only be done as the last resort as it is a major PIA. Been there.

Try this for the modulator cap:1984 Mercedes-Benz 300TD Wagon - Automatic Transmission - Page 3

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Sam

84 300SD 350K+ miles ( Blue Belle )

Yea, I ordered my trans filter kit from there! Guess I got to writing instead of looking there first!

That being said, it definitely looks like a PITA to get in there. All the pictures look like there is enough room to put two hands up there!

When I started the vac check I went to remove the line from the brake booster and "break" it did. Just got the new part and new vac tubing and I'll see how that works out. Maybe the kit will work some of it out and replacing the vac tubing by the modulator will help a little, since it slipped right off easily. The modulator still didn't hold pressure so I can't see the tubing as the full culprit.

__________________
1980 300TD, SOLD
1984 300TD, 275K
1999 C230 K Black & Tan
2013 C250 Black
1974 CJ5 Red
You might faint from the fight, but you're gonna find it. Every challenge could have paradise behind it. -John Popper-