85 300D downshift clunk????` - PeachParts Mercedes-Benz Forum

meltedpanda · #1 11-11-2008, 05:20 PM

Shifts up as I would expect, firm , no flair, some minor delay. 212K on the clock , coming down from speed , clunk to second, bigger clunk to 1st
Any ideas???
Be gentle

johninva · #2 11-11-2008, 05:47 PM

vacuum leak

bgkast · #3 11-11-2008, 06:02 PM

How are your flex disks and how is your center driveshaft bearing?

meltedpanda · #4 11-11-2008, 06:04 PM

I thought about all three ideas, the flex discs look good, where is driveshaft bearing - will it have play?
Vacuum leak - Where do you check , i have a mity vac

bgkast · #5 11-11-2008, 06:10 PM

I'm not sure the vaccum affects downshifts that much. Best bet is the center bearing. It's located under the car just about between the front seats. Crawl under there, grab the drive shaft and check for play.

UriahT · #6 11-11-2008, 08:11 PM

Vacuum affect downshifting a lot.

When I had a significant vacuum leak, my downshifts were incredibly loud clunks that you could feel. Now that the vacuum is under control to my transmission, the clunking is still there, but very minimal, and you can't feel it.

There are a ton of threads on the subject, but make sure vacuum from the VCV to the transmission is 12-15 at idle, and drops to 0 when fuel rack is fully open. It's the idle vacuum level that matters most- that's what the rack sensor sees when downshifting to a stop.

meltedpanda · #7 11-11-2008, 08:17 PM

and VCV is ??? and located ????

sixto · #8 11-11-2008, 08:23 PM

Post a picture of the diff mount.

Sixto
87 300D

kerry · #9 11-11-2008, 09:17 PM

It's a vacuum leak in your ACC system now becoming evident because the weather is getting cold and you're running the heater. Try pushing in the far right button on the heater control array and see if the clunking goes away. If it does, my diagnosis is confirmed.

Brian Carlton · #10 11-11-2008, 11:14 PM

Quote:

Originally Posted by meltedpanda

and VCV is ??? and located ????

You've been here for five years...........have over 2,000 posts...........and by now, you should understand how to use the search function. We've discussed how to check and fix low vacuum conditions about 200 different times in the archives and the procedure is always the same.

Kindly make a bit of effort to do some research on how the system works..........what a VCV is.........and start troubleshooting it. If you get stuck..........then, we'll help you.

Sorry if I'm a bit annoyed about this situation, but the forum has deteriorated into a group of people who will not make the slightest effort to educate themselves on the topic at hand before posting with a request for an immediate fix.

daw_two · #11 11-12-2008, 08:09 AM

Quote:

Originally Posted by Brian Carlton

You've been here for five years...........have over 2,000 posts...........and by now, you should understand how to use the search function. We've discussed how to check and fix low vacuum conditions about 200 different times in the archives and the procedure is always the same.

Kindly make a bit of effort to do some research on how the system works..........what a VCV is.........and start troubleshooting it. If you get stuck..........then, we'll help you.

Sorry if I'm a bit annoyed about this situation, but the forum has deteriorated into a group of people who will not make the slightest effort to educate themselves on the topic at hand before posting with a request for an immediate fix.

Brain.

I feel your pain. In an effort to offer constructive criticism, I'll suggest that maybe the SEARCH function should be (could be) improved. Make it more PRONOUNCED in the menu. Make it FLASH. Change it to read...... "SEARCH for YOUR ISSUE and RESOLUTION". Okay, you understand what I'm attempting to say, so I'll stop kicking the dead horse.

The use of the Google has helped. Maybe we could make it a STICKY? How about a STICKY on how to use this Forum. It could cover everything from searching, how to make a post, where the DIY are located (I still have trouble finding them), the basic rules (no CarFax info), etc. There's a lot things I've had to sort of learn on my own because no one told me. How about when people sign up, they have to mandatory read and click thru a few things during their first week before they can post?

I'm just throwing out ideas to try to improve the board.

Sorry for hijacking the Original Poster's thread.

Brian Carlton · #12 11-12-2008, 08:18 AM

Quote:

Originally Posted by daw_two

Maybe we could make it a STICKY? How about a STICKY on how to use this Forum. It could cover everything from searching, how to make a post, where the DIY are located (I still have trouble finding them), the basic rules (no CarFax info), etc. There's a lot things I've had to sort of learn on my own because no one told me. How about when people sign up, they have to mandatory read and click thru a few things during their first week before they can post?

Check out the sticky that's already there: "Troubleshooting........get the most from your post".

You can drag the horse to water...........but, you can't make him drink.

rs899 · #13 11-12-2008, 08:26 AM

..what Brian said.

But we also need to be more careful how we title our posts.

one called "HELP" is not going to be very useful in a search. I realize it may get more attention to be cute, but when you sort through a bunch of potentially useful threads it is hard to say from the titles what one is looking for.

I concur that it is likely the VCV that is out of adjustment or bad, in this case. Personal experience.

meltedpanda · #14 11-12-2008, 09:07 AM

Brian , Brain, I stand ashamed at my behavior........

You are correct - plain and simple
how many push ups should I do?

Brian Carlton · #15 11-12-2008, 09:13 AM

Quote:

Originally Posted by meltedpanda

Brian , Brain, I stand ashamed at my behavior........

You are correct - plain and simple
how many push ups should I do?

Don't worry about it............and you're just the straw that broke the camel's back. All I tend to see are posts by new folks who want an immediate fix to a complicated issue and they can barely open the hood.

Personally, I'm not posting on those threads..........some effort is required by the owner to fix their vehicle...........we don't have a pill that we can send in the mail.