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 03-28-2008, 12:15 AM
Registered User
 
Join Date: Apr 2007
Location: New Orleans
Posts: 66
Transmission Leaks in reverse only! Front seal?

An easy one (I hope) for all you tranny experts: My 82 300TD has been leaking a significant amount of fluid when the engine is cold and I put it into reverse as i can always see a trail of fluid following me into a parking spot. based on the amount of fluid that comes out in reverse and how often I need to add transmission fluid (about 1 quart per 1,000 miles) i am probably also leaking a small bit when I am moving forward and know it leaks a bit at idle but not nearly as much as when i'm in reverse. The leak is coming from the front of the transmission where it attaches to the engine, ahead of but not from the torque converter.

Am I correct to assume it is the front main seal leaking? Are there any other seals I should replace when I drop the tranny or any other diagnostic tests I should run on it prior to dropping it? I have the filter kit and gasket.

I have to replace my starter so I have decided to go for the transmission at the same time with the help of a friend who has all the tools and has done this job many times. i'm feeling a bit apprehensive about such a big job but it has to be done. Any and all advice and support appreciated.

peace,
woody
__________________
peace,
Woody
Reply With Quote
  #2  
Old 03-28-2008, 12:26 AM
AHH,What's up Doc????
 
Join Date: Jul 2006
Posts: 1,212
It's possible that the front seal is shot, but I'm not sure about it leaking more in reverse. I'm willing to bet the leak is the same going forward or backwards, but you probably notice it more when you back up and the fluid sloshes out toward the front of the bell housing. Either way this is going to be a big job because you will have to remove the transmission to fix this. Once you get it apart however, replacing the seal is fairly easy!
Reply With Quote
  #3  
Old 03-28-2008, 12:33 AM
Registered User
 
Join Date: Apr 2007
Location: New Orleans
Posts: 66
I assure you it leaks a significant amount in reverse and very little in drive. I have been taking note of this for quite some time. If it leaked the way it does in reverse while moving forward I would have to be adding fluid after every couple hours of driving.

Now after rereading your post I hear you saying that when i am moving in a forward direction the fliud is pushed back toward the rear of the transmission an when going in reverse it moves to the front. this would make sense and would seem to explain what is going on. Any other opinions and theories welcome
__________________
peace,
Woody
Reply With Quote
  #4  
Old 03-28-2008, 12:34 AM
turbobenz's Avatar
Registered User
 
Join Date: Nov 2007
Location: Cameron Park CA
Posts: 1,863
what causes a front seal to go out? I know rubber will usualy stay good forever unless sun hits it. What im saying is why does his seal leak, while so many of the same mileage dont.
__________________
1981 300SD 512k OM603


Reply With Quote
  #5  
Old 03-28-2008, 06:28 AM
Admiral-Third World Fleet
 
Join Date: Feb 2002
Location: Central FL
Posts: 3,068
Might possibly be the o-ring around the reverse band servo (probably the front one ) is bad or not seated. IF that is really the case ( and not just a faulty "reverse only" diagnosis) you might not have to pull the tranny to get to it. Take a look at a manual to see where reverse band is located on the 722.3xx and see if that could be the leak area.

Quote:
you probably notice it more when you back up and the fluid sloshes out toward the front of the bell housing.
and

Quote:
I hear you saying that when i am moving in a forward direction the fliud is pushed back toward the rear of the transmission an when going in reverse it moves to the front
This really is not the case here. Apart from what tiny bit is left in the pan, the fluid is being carefully directed at the servos and clutches to make your car do what you tell it to do. There isn't anything "sloshing" near the bell housing.

Best course of action is to pressure wash your tranny, then get the car up on a lift and run it through the gears to see where the leak is coming from.

Rick
__________________
80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)

Last edited by rs899; 03-28-2008 at 06:35 AM.
Reply With Quote
  #6  
Old 03-28-2008, 08:55 AM
C Sean Watts's Avatar
NOCH EIN PILS!!
 
Join Date: Mar 2006
Location: NC
Posts: 1,318
except for

Quote:
Originally Posted by turbobenz View Post
what causes a front seal to go out? I know rubber will usualy stay good forever unless sun hits it. What im saying is why does his seal leak, while so many of the same mileage dont.

Heat, oil and ground level ozone. Not being a smarty pants, but, unless we can find Viton or silicone seals leaks will happen.
__________________
1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!
Reply With Quote
  #7  
Old 03-28-2008, 11:45 AM
Mustang_man298's Avatar
Man of the fire
 
Join Date: May 2006
Location: Shingletown,Ca
Posts: 941
Quote:
Originally Posted by rs899 View Post
Might possibly be the o-ring around the reverse band servo (probably the front one ) is bad or not seated. IF that is really the case ( and not just a faulty "reverse only" diagnosis) you might not have to pull the tranny to get to it. Take a look at a manual to see where reverse band is located on the 722.3xx and see if that could be the leak area.



and



This really is not the case here. Apart from what tiny bit is left in the pan, the fluid is being carefully directed at the servos and clutches to make your car do what you tell it to do. There isn't anything "sloshing" near the bell housing.

Best course of action is to pressure wash your tranny, then get the car up on a lift and run it through the gears to see where the leak is coming from.

Rick
Agreed. Fluids will slosh a bit as the vehicle moves, but it is minimal and they arent "forced" anywhere unless pumped. The front pump always runs when the engine turns, and is always maintained at a steady pressure no matter what the trans is doing, so what gear you're in will have no effect. Usually when that seal goes, you know it in a hurry, it will just spew like the dickens and you'll find yourself out of fluid in very short order. I'm banking on what Rick said, you have a servo cover leaking somewhere, one that is applied in reverse, maybe also in a forward gear but at a point where you don't see the trail due to being spread out from speed. I've also seen some posts on here about servo covers fracturing. Your leak could be running down the side of the trans to the place where you see it drooling off. Clean it off and watch for it before you pull the trans needlessly.
__________________
Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale
Reply With Quote
  #8  
Old 03-28-2008, 11:47 AM
Registered User
 
Join Date: Apr 2007
Location: New Orleans
Posts: 66
Quote:
Originally Posted by rs899 View Post
Might possibly be the o-ring around the reverse band servo (probably the front one ) is bad or not seated. Take a look at a manual to see where reverse band is located on the 722.3xx and see if that could be the leak area.
What manual would you recommend and where would I find it?


Quote:
Originally Posted by rs899 View Post
Best course of action is to pressure wash your tranny, then get the car up on a lift and run it through the gears to see where the leak is coming from.
The leak is coming from the small gap between the front of the transmission and rear of the engine where they connect with one another.

Thanks for the input
__________________
peace,
Woody
Reply With Quote
  #9  
Old 03-28-2008, 11:55 AM
Admiral-Third World Fleet
 
Join Date: Feb 2002
Location: Central FL
Posts: 3,068
If you are sure that's where it is coming from, you will have to pull it to fix it. I have no idea why reverse would affect the leak any more than a forward gear. As MM said, you are talking about the front pump that is always going the same direction under the same load. Good luck with that....
__________________
80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)
Reply With Quote
  #10  
Old 03-28-2008, 12:02 PM
AHH,What's up Doc????
 
Join Date: Jul 2006
Posts: 1,212
Quote:
Originally Posted by rs899 View Post
Might possibly be the o-ring around the reverse band servo (probably the front one ) is bad or not seated. IF that is really the case ( and not just a faulty "reverse only" diagnosis) you might not have to pull the tranny to get to it. Take a look at a manual to see where reverse band is located on the 722.3xx and see if that could be the leak area.



and



This really is not the case here. Apart from what tiny bit is left in the pan, the fluid is being carefully directed at the servos and clutches to make your car do what you tell it to do. There isn't anything "sloshing" near the bell housing.

Best course of action is to pressure wash your tranny, then get the car up on a lift and run it through the gears to see where the leak is coming from.

Rick
Correct. Fluid under pressure will not be sloshing around, but I was referring to a little that could be puddling in the bell housing as the front seal dribbles it out. The front seal should be under the same amount of pressure regardless of which way the vehicle is moving because the engine only rotates one way!

I'm not sure why it would be coming out more in reverse from in there with the system under pressure.
Reply With Quote
  #11  
Old 03-28-2008, 12:26 PM
Registered User
 
Join Date: Nov 2004
Location: Nova Scotia, Canada.
Posts: 6,510
The only viariable I can think of is the bellhousing to engine bolts loose. Torque while reversing changes the direction of torque to the transmission case. This may change the alignment of the input shaft just enough to make a leaking front seal leak even more. Remember he said it pours out when in reverse. Also could account for the seals overall failure.
If you find the bellhousing bolts loose keep this in mind. A very long shot but something has to explain this oddity. If those bolts were really loose I might just tighten them up and test before pulling the transmission. If you do find anything unusual in the repair process let us know.

Last edited by barry123400; 03-28-2008 at 12:32 PM.
Reply With Quote
  #12  
Old 03-28-2008, 10:16 PM
Registered User
 
Join Date: Apr 2007
Location: New Orleans
Posts: 66
I am sorry to have to ask this question but what is a servo, what function do they perform, how many are there in the transmission and how do i check them to make sure they are all sealed correctly, not cracked etc....? In the meantime i will happily check the bellhosing to engine bolts to see if they are tight and hope they are not. if only i could be so lucky; please!!!
__________________
peace,
Woody
Reply With Quote
  #13  
Old 03-28-2008, 11:24 PM
Registered User
 
Join Date: Nov 2004
Location: Nova Scotia, Canada.
Posts: 6,510
I am used to electrically controlled servos being used in other fashions. You could say the starter solenoid is a servo for example. Basically it is a device that a control signal makes perform a secondary function. In this case the controlled hydralic pressure activates the device and makes it tighten a band around a drum. Like an external brake lining on that band locks the drum up when it is tightened.
Just make absolutley certain you have the area where the fluid is coming out before pulling that transmission. Even if you have to put the back end of the car up on jackstands and run the car in reverse. I do not know for certain how many servos there are in this transmision. Two-three strikes me as about right. You at least are only concerned with leakage from them externally anyways. A shot gasket, O ring or cracked cover type of thing as a previous poster mentioned.
Search the archives on how to change front transmission seals and other related things. Others will post better information as well.
I am far from knowledgeable about automatic transmissions. What you are hunting for is within your abilities to find and repair. You are not going into the transmission. At this point you can easily understand why some people thought it was the reverse band solenoid. Hydralic oil under pressure is only directed to it when reverse is selected.
Reply With Quote
  #14  
Old 03-29-2008, 01:11 PM
Registered User
 
Join Date: Apr 2007
Location: New Orleans
Posts: 66
Quote:
Originally Posted by barry123400 View Post
Search the archives on how to change front transmission seals and other related things. Others will post better information as well. I am far from knowledgeable about automatic transmissions. What you are hunting for is within your abilities to find and repair. You are not going into the transmission. At this point you can easily understand why some people thought it was the reverse band solenoid. Hydralic oil under pressure is only directed to it when reverse is selected.
Tomorrow i am going to put the car up on Jack Stands, clean off under the bell housing, and run it in drive and reverse to make completely sure as to what is going on under there. from there i will make a decision to either pull the transmission and reseal or try and locate and inspect the reverse band solenoid before pulling the entire transmission out of the car. If anyone reading this has any idea how i can get to the reverse band in order to check it out I would greatly appreciate hearing about it as I have no clue where it is and have no manual that tells me such. As always thanks for the assistance.
__________________
peace,
Woody
Reply With Quote
  #15  
Old 03-29-2008, 05:02 PM
Registered User
 
Join Date: Nov 2004
Location: Nova Scotia, Canada.
Posts: 6,510
If the transmission is leaking around an opening in the transmission with a small cover you will see it. Then describe it's location well and others can suggest what to do.
Repair should be managable without pulling the transmission then. If it is still originating between the belhousing and engine that is another story. Out with the transmission.
Also have a look to make sure the transmission dipstick tube appears inserted and dry around it. Thought about this yesterday but again do not know any mechanisim that would make it leak more in reverse than in forward gears. Sometimes things happen occassionaly that are hard to rationalise.
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 12:20 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, 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