Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 05-25-2009, 05:08 PM
ashedd's Avatar
Registered User
 
Join Date: Aug 2008
Location: Seattle
Posts: 1,790
Replaced Vac lines now hard shifting

I replaced every rubber vacuum line I could find under the hood of my 87 300D. Now the shifts are really harsh. Lot's of horrible clunks and pop's from the rear end during normal shifts. If I accelerate moderately the shifts smooth out a bit. The down shifts are harsh as well.

Before the replacement of the vac lines the shifts were pretty good with the exception of the transmission kinda not knowing what gear to be in sometimes.

If I had this problem with my SD I would adjust the modulator to smooth out the shifting... I looked under the 300D today and could not see a modulator to adjust.

The shifts now feel very firm and good. The shift points are spot on as well. It just the darn rear end noise

Thanks
__________________
08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

Reply With Quote
  #2  
Old 05-25-2009, 07:13 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,315
The modulator is on the driver side of transmission as it is in the 83 300SD.

The vacuum control valve (VCV) is on the side of the IP. There are two vacuum lines attached to the top and a black vent line on the side. To set, loosen the two bolts that take a 10mm wrench holding the VCV to the IP, turn the VCV all the way CCW, prop the throttle linkage at WOT, slowly turn the VCV CW until you just feel resistance, tighten the bolts.

Sixto
87 300D
Reply With Quote
  #3  
Old 05-25-2009, 07:56 PM
ashedd's Avatar
Registered User
 
Join Date: Aug 2008
Location: Seattle
Posts: 1,790
I will give it a try. Thanks

On a side note....


I have not driven the 300D in a while until today... OM603 always puts a smile on my face. I wonder what 200ish HP would feel like
__________________
08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

Reply With Quote
  #4  
Old 05-25-2009, 11:30 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,315
Would feel like a big hole in your wallet

Sixto
87 300D
Reply With Quote
  #5  
Old 05-26-2009, 01:20 AM
scottmcphee's Avatar
1987 w124 300D
 
Join Date: Mar 2008
Location: Edmonton, Canada
Posts: 1,539
Quote:
Originally Posted by sixto View Post
The modulator is on the driver side of transmission as it is in the 83 300SD.

The vacuum control valve (VCV) is on the side of the IP. There are two vacuum lines attached to the top and a black vent line on the side. To set, loosen the two bolts that take a 10mm wrench holding the VCV to the IP, turn the VCV all the way CCW, prop the throttle linkage at WOT, slowly turn the VCV CW until you just feel resistance, tighten the bolts.

Sixto
87 300D
You know I didn't trust this advice at first... I was having good luck adjusting the "advance" of this VCV and even wanted to turn it CW beyond max - because I had what I thought is unusually high 15 inHG vac at idle and wanted to bring it down to around 10... to reduce the range of vac from 10-0 going to the vac amplifier...

Anyway, I had my IP off this weekend and I see that the VCV pivots on the exact same axis as the go-pedal linkage on the other side of the IP. If you over-rotate the VCV clockwise beyond the 'resistance point' what you are in fact doing is not permitting the the accelerator to reach it's bump stop limiter. You're not allowing max input to the IP. Even though you might be allowing vac to drop sooner with this strategy, maybe to help your shifting, you take away top end power.

I believe now.

Sixto I wish you gave a short version of this reason as to why you don't go beyond the resistance point in your accompanying good advice, then schmeebs like me would probably attempt fewer dumb things...

Put the VCV in its right spot and I'm seeing a good healthy drop from 15 or so to zero, on warm engine, with turbo pumping... So I'll leave it there and move on to the next thing in trying to get the gremlins out of my shifting. Too soon upshifts, a little soft, 2-3 and 3-4 too close together.

Bowden cable, white nut, that's next... Before I go crawling for a modulator under the car.
__________________
Cheers!
Scott McPhee

1987 300D
Reply With Quote
  #6  
Old 05-26-2009, 01:55 AM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,315
I was thinking about just that. Seems to me an alternative way to set the VCV is to turn it full CW with the throttle at WOT then let the negator spring turn it back CCW until the spring is relaxed. That ensures you don't inadvertently set it as a throttle limit.

But what I posted is basically all the FSM tells you about setting the VCV. Maybe there's more discussion in the IP section.

Sixto
87 300D
Reply With Quote
  #7  
Old 05-26-2009, 03:48 PM
ashedd's Avatar
Registered User
 
Join Date: Aug 2008
Location: Seattle
Posts: 1,790
I did the adjustment today. Seemed to help out a lot. I am still have a clunk in the rear end area. I have yet to have this car on a lift, I have never even really looked under it. This Saturday I will get it on a lift to replace a tie rod.

I am going to look at the flex disk's and halfshafts. To me those two things sound like the culprit. Kinda sounds like an old American car that needs U-joints real bad.

Sound like a good plan of attack?
__________________
08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

Reply With Quote
  #8  
Old 05-26-2009, 10:39 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,315
My guess on the clunk is the diff bushings are shot. Those would be the two you can see from behind the diff. The left one takes a heck of a beating. If the bolt isn't centered in the bushing, it's gone.

Sixto
87 300D
Reply With Quote
  #9  
Old 05-26-2009, 11:14 PM
ashedd's Avatar
Registered User
 
Join Date: Aug 2008
Location: Seattle
Posts: 1,790
Quote:
Originally Posted by sixto View Post
My guess on the clunk is the diff bushings are shot. Those would be the two you can see from behind the diff. The left one takes a heck of a beating. If the bolt isn't centered in the bushing, it's gone.

Sixto
87 300D
So it sounds like the rear diff mount/set up is not the same as my SD. I can't wait to get it on the lift later in the week.

Sixto your a wealth of information-Thanks
__________________
08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D

Reply With Quote
  #10  
Old 05-26-2009, 11:33 PM
sixto's Avatar
smoke gets in your eyes
 
Join Date: Jun 2000
Location: SF Bay Area
Posts: 20,315
Goodness, very not the same. A complete PITA to replace them too. Diff has to come off! There are a couple of bushings atop the snout of the diff.

Sixto
87 300D
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 08:57 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page