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 12-07-2004, 05:15 PM
Registered User
 
Join Date: Nov 2003
Location: northern VT
Posts: 537
Transmission shifting question

I have Just managed to drive my 84 300TD for the first time since dragging it home on November 10th. I am not sure what to think about it's shift quality. Granted I only put about 10 miles on the car, and most of it was with a death grip on the wheel, as I have since discovered that the steering shock absorber link is missing on it.

Any way My observations are that it will sometimes flair at about 20MPH, with the motor running about 2000 RPM. Is that a 2nd to 3rd shift? or 1st to 2nd? I had a hard time figuring out which gear I was in.

Sometimes the first shift was a tad harsh, but not always...
The flair could be regulated by closing the throttle, allowing the transmission to hook up.... and it would not slip upon reacceleration.

Does it sound like I need to find another car for the winter?
Or can I get it to run for another 8/10 thousand with the proper adjustments, and rebuild it next summer?

Jason
__________________
46 WDX Power Wagon

84 300TDT daily driver
Reply With Quote
  #2  
Old 12-07-2004, 05:53 PM
Registered User
 
Join Date: Sep 2004
Location: Bothell, WA
Posts: 237
Based on my own experimentation I would say that shift quality such as you describe is down to vacuum adjustment first, and transmission modulator functioning second. Both can be fixed without really touching the transmission.

My car has a different transmission to yours, but by that speed I'm well out of first. My 1st to 2nd shift is so smooth you can miss it if not feeling very carefully, I would guess you're seeing the 2nd to 3rd shift.

Last weekend I bought a vacuum/pressure gauge at NAPA for $30, it has a nice, clear, 3 1/2" dial. I already had a mity-vac vacuum pump without a gauge. By refering to vacuum diagrams readily available through this site I was able to troubleshoot my entire vacuum system as it relates to transmission shifts, and make changes to the behavior.

Buy yourself 6 feet of vacuum hose while you're at the auto parts store. Using the mity-vac, a T piece, and the gauge you can work your way around the various vacuum circuits checking to make sure that the devices that are supposed to hold vacuum, do. I found that my EGR valve and air recirc plumbing were leaking, so I just isolated that whole mess out of the circuit. Every straight rubber connector was replaced with an inch or two of vacuum hose from the 6' length.

Now with the engine running you can check the various circuits that are supposed to have vacuum, and confirm that they do and how much. The vacuum circuit has restrictors in various places that can eventually become clogged. Remember to keep in mind that the vacuum circuit is constantly sucking air through all those pipes into the vacuum pump. The air that is being sucked in may come from inside the cabin, or a lose connection somewhere, and eventually atmospheric gunk clogs the works - this was the case with my car.

In my view a couple of hours spent with a vacuum gauge and diagram should have you in good shape.

Kevin
__________________
'85 300SD
Reply With Quote
  #3  
Old 12-07-2004, 07:22 PM
Jimmy Joe's Avatar
peace out
 
Join Date: May 2004
Location: California central coast
Posts: 1,004
sure wish I could figure mine out.
very harsh shifts.
I have just gotten used to it, can't solve the problem
Anyone in the SF Bay area want to take a look for a case of beer?
__________________
Think Alternative Energy!
300CD '80 (now gone but not forgotten...)
Reply With Quote
  #4  
Old 12-07-2004, 08:55 PM
Registered User
 
Join Date: Nov 2003
Location: northern VT
Posts: 537
Kevin,
Thanks for the optimistic advice. I will get to it tomorow, and even go shopping for a mity vac unit. Now I will do some reasearch on how the vacume system is set up. it still looks like a bunch of wires to me, and the parts car has some different kind of system, so it is hard to tell which one is more correct.
Jason
__________________
46 WDX Power Wagon

84 300TDT daily driver
Reply With Quote
  #5  
Old 12-07-2004, 09:25 PM
younger than most trees
 
Join Date: Jun 2004
Location: Albuquerque
Posts: 88
Shifting

After driving my '83 TD for a couple years and NEVER being satisfied with the shifting, I am convinced that the only fix was a conversion to a manual tranny. It truely is the best thing I have ever done for the car. (see other threads relating to this issue) The web is loaded with advice about curing the w123 tranny glitches. That was my first clue! I tried all things possible short of a rebuild ($2.5-$3k minimum) and the cost of a conversion, doing my own work, was about $900. I love it! - Jacob
Reply With Quote
  #6  
Old 12-07-2004, 10:19 PM
Registered User
 
Join Date: Sep 2004
Location: Bothell, WA
Posts: 237
Jacob

A rebuilt transmission is around $1,200, not $2.5 to $3K.

Kevin
__________________
'85 300SD
Reply With Quote
  #7  
Old 02-02-2005, 09:43 PM
younger than most trees
 
Join Date: Jun 2004
Location: Albuquerque
Posts: 88
The shop I go to when I'm in over my head will supply an automatic rebuild, from their recommended and waranteed source for $2.5k +$490 install. The manager agrees that the manual conversion is a very desireable.
Reply With Quote
  #8  
Old 02-03-2005, 02:48 AM
Jimmy Joe's Avatar
peace out
 
Join Date: May 2004
Location: California central coast
Posts: 1,004
I am interested in this, but don't have an alda.
I do have that 3/2 valve doohickey.
Wonder if this will work for me....
__________________
Think Alternative Energy!
300CD '80 (now gone but not forgotten...)
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 04:05 AM.


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