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 03-27-2010, 11:23 PM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
84 300CD shift problems

Just got an 84 300cd-

It shifts hard into first and second, close together. I fiddled with the EGR and vacuum hoses and have it working a little better, with mixed results.

The transmission seems to work irregularly. Today after first messing with the EGR, I felt like I got more torque but the transmission wasn't shifting as long as I pressed the throttle. I also started to notice the "thunk" in the rear end when approaching stop.

I blocked off the EGR at the valve using the soda can method. Then i disconnect all the hoses from the black box, plugged up the orifices and turned the three way connectors around the VCV into two-ways. I think I got all of this right.

It still shifts hard, but at around 3,000RPM, is this correct?

I've tested vacuum using this chart:
http://www.peterschmidtransmission.com/vacuum/1977_1985/617_95/1981_1984.jpg

I get over 20psi at idle at all points except for at the VCV itself, which I understand isn't supposed to hold vacuum but leak it. At the VCV I get 10psi.

Vacuum is strong at point "b"- to the transmission. Does this mean my transmission modulator is okay?

What else should I check? Help would be greatly appreciated.

Reply With Quote
  #2  
Old 03-27-2010, 11:35 PM
tfernandez's Avatar
Registered User
 
Join Date: Sep 2009
Location: Orlando, FL
Posts: 175
is it when you first fire up the car? or all the time when you are driving?

from what it sounds like, its a very common thing (my 300cd does it too)
from what ive been told, it's designed so that when the pedal is heavily pressed, it will shift as described. if you find the sweet spot on the pedal it should shift properly and smooth. also, when you are pressing heavily, slowly release when you get to a shift point and it should shift a little smoother.
__________________
1984 W123 300CD silver/blue *230k*
http://www.fuelly.com/sig-us/45166.png
Reply With Quote
  #3  
Old 03-28-2010, 11:00 AM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
*^@#&$*

Okay, things just took a turn for the worse. I got in the car this morning, and was surprised by how smoothly it was shifting. I was impressed until I tried to go up a hill, and barely made it to the top.

I have to floor it in first and second to get any acceleration, then it won't shift into fourth. Only getting 3 gears. I can only get up hills by shifting manually.

Any Ideas?
Reply With Quote
  #4  
Old 03-28-2010, 11:54 AM
compress ignite's Avatar
Drone aspiring to Serfdom
 
Join Date: Feb 2004
Location: 32(degrees) North by 81(degrees) West
Posts: 5,554
Transmission Chronicles

First Advice is ALWAYS change the Transmission Fluid and Filter
(This includes Draining the Torque Converter, as well as the Pan.)
'Be Bloody Amazed how many problems are rectified by this oft neglected
Service item.

Transmission:

How many miles on the transmission?

My Favorite One is that "Adjusting" a Mercedes Transmission is kinda like buildinga Pyramid UpSide down.
All your Basic blocks have to be ordered/"Adjusted" in the correct sequence.
(Or, you're Navigating with a Black Felt bag over your head.You have No Ideawhere you are, even though you THINK you do.)
No "Seat of the Pants" flying,Capiche ?
1st basic: Is the engine "Making Power" correctly?
(Many "Alleged" transmission problems are simply disguised engine problems)

Stevebfl has some great tips.

Samuel M. Ross advises on Vacuum.
__________________
'84 300SD sold
124.128

Last edited by compress ignite; 03-28-2010 at 12:02 PM.
Reply With Quote
  #5  
Old 03-28-2010, 04:44 PM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
So I spent the morning adjusting the Bowden cable, and it seemed like positioning it correctly solved most of my problems.

The car shifted smooth, tons of torque, easily hit 85 on the highway. Everything was going great for about two hours, until I started to struggle again. 70-80MPH runs around 3000-3500 rpms in my car-- tachometer slowly drops below 3,0000, and the car slows down to around 60mph which it struggles to maintain, full throttle.

This happened intermittently for the rest of the drive. It felt like a fuel issue- is this just another reason to change the filter?

What does the kick-down do?
Reply With Quote
  #6  
Old 03-29-2010, 12:17 AM
tfernandez's Avatar
Registered User
 
Join Date: Sep 2009
Location: Orlando, FL
Posts: 175
Quote:
Originally Posted by ivandrocco View Post
So I spent the morning adjusting the Bowden cable, and it seemed like positioning it correctly solved most of my problems.

The car shifted smooth, tons of torque, easily hit 85 on the highway. Everything was going great for about two hours, until I started to struggle again. 70-80MPH runs around 3000-3500 rpms in my car-- tachometer slowly drops below 3,0000, and the car slows down to around 60mph which it struggles to maintain, full throttle.

This happened intermittently for the rest of the drive. It felt like a fuel issue- is this just another reason to change the filter?

What does the kick-down do?
assuming you just bought the car, ALWAYS CHANGE YOUR FUEL FILTERS!!!!!!!! again, mine was the same way when i bought it. quick change of BOTH the primary and secondary fuel filters should fix the loss of acceleration and power. a diesel purge might be a good idea too, and (im not sure if this will effect it as well) maybe replacing your return fuel lines seeing as it is very cheap to do.
the kickdown (if i recall correctly) downshifts the car for a sudden burst of acceleration.
I remember once I was driving to school, and not but 100 feet away was a huge 30 foot hill (in florida of all places) i could barely go 25 and everyone was very... perturbed hahah. good to hear the car is running well other then your clogged filters. take some pictures if you can
P.S. how much did you pick the car up for?
__________________
1984 W123 300CD silver/blue *230k*
http://www.fuelly.com/sig-us/45166.png
Reply With Quote
  #7  
Old 03-29-2010, 06:20 PM
ivandrocco's Avatar
Registered User
 
Join Date: Mar 2010
Location: Amherst, MA
Posts: 243
I was looking all over getting frustrated, so I decided to check out a local MB shop that usually has a few 300d's on their lot. Now that gas is cheap and the interest in WVO conversions has waned a bit, the mechanic was asking a few thousand less than he was a few years ago. I talked him down to $2500.

The car was owned by an MB collector who used it as a commuter. The mechanic services his cars, and took it in on a trade for a w124.

It has a few problems. Some body work in the front fenders, the front left panel is a few mm out of alignment, most of this is covered up by a decent paint job done last year. Also a leak in the passenger side foot well, needs new upper control arms... minor stuff. The car has 190k miles, and generally runs pretty nice. Not a bad deal?






I was half in the bag last night and bought this steering wheel on Ebay- even though it's probably the last thing this car needs and I can't afford it. But hey, at least it will match my shifter!

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=150426130584&ssPageName=ADME:X:RTQ:MOTORS:1123#ht_500wt_975

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 08:08 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2023, 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