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 > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 04-09-2004, 01:44 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
722.3 Transmission Troubles

My 380SL is having some strange transmission troubles. When cold, the trans shifts well. When warm, after perhaps two miles of driving, after coming to a stop, it will start in second gear and have a terrible flaring shift into third. The shift to fourth is OK but a bit soft. If you shift into Low at the stop, it feels like the brakes are on when you move off.

I just had the transmission tested. The findings were

- working pressure 210 PSI in Drive, idling - out of limits
- modulating pressure 60 PSI - 30% high
- valve body regulating OK

Recommendation was for a rebuilt trans or to go into this one and replace the K1 and K2 packs.

Now here's the kicker. When I drove the car home from the shop, I discovered that, if at the stop, I shift to Neutral and then back to Drive, it starts in first and changes up through the gears very nicely with the exception of the soft shift to fourth.

I called the tech and reported this. At first he expressed disbelief, but after we got past that, he could not think of a reason for this behavior. It seems to me that if the trans is left in gear at a stop, something is preventing it from going properly into first gear.

Anybody have a clue?

TIA

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
Reply With Quote
  #2  
Old 04-09-2004, 08:24 PM
C32AMG's Avatar
Registered User
 
Join Date: Mar 2004
Location: new york/orange county
Posts: 639
With that high pressure reading your car should be slamming all gears and breaking parts with that 722.301 1st gear start valve body.

Normal working pressure in drive is 90 to 110 PSI modulator at 51PSI.
The 722.3, 4, 5 and 6 transmissions have a rare problem of breaking the pressure regulator spring; you, say the car shifts well when cold.


Here is my guess, the PR spring broke, pieces ended up throughout the valve body causing the pressure regulator valve to stick, hence the abnormal pressures, also sticking shifts valves, soft flair up shifts. If the oil is clean with no burnt smell and the pan also clean with no metal. Then try another valve body.
Reply With Quote
  #3  
Old 04-09-2004, 09:26 PM
jbaj007's Avatar
Registered User
 
Join Date: Jun 2001
Location: Santa Monica, CA
Posts: 2,053
May help, may not; but worth reading:
http://www.transmissionspecialty.com/parts/parts/68942-01.htm
__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
Reply With Quote
  #4  
Old 04-10-2004, 08:09 AM
BlackBeauty's Avatar
BRABUS'ed
 
Join Date: Feb 2003
Location: South East Asia
Posts: 125
Since we are at the topic of auto transmissions, I have a 90' 300CE. After a spirited drive about 2 weeks ago, my 1-2 gear change started shifting "harder than normal". Kind of like a shift shock but only happens on 1-2 and 2-1 gear changes (my tranny has a 2nd gear start). On the other gear changes, still like before and very smooth. I'm puzzled!!!

Amy feedback??

Rgds
Reply With Quote
  #5  
Old 04-10-2004, 05:26 PM
Super Moderator
 
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
C32 and jba - thanks for the suggestions. I think that I will order a replacement spring from Sonnax and have a look at the pressure regulator.
__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
Reply With Quote
  #6  
Old 04-10-2004, 07:53 PM
jbaj007's Avatar
Registered User
 
Join Date: Jun 2001
Location: Santa Monica, CA
Posts: 2,053
If you do find a fractured spring, be sure to reassemble it on the bench and measure it. That way you'll know that there isn't an errant piece still inside the tranny. Good luck.

By the way. I picked up a new and improved valve spring kit for this at the dealer. Wasn't too bad a hit, as I recall.
__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
Reply With Quote
  #7  
Old 04-10-2004, 09:55 PM
C32AMG's Avatar
Registered User
 
Join Date: Mar 2004
Location: new york/orange county
Posts: 639
chuck,
Post what you find, for future reference


Black beauty,

The cause of a Harsh 1 - 2 and 2-1shift, could be a sticking, 1 -2 accumulator piston in the VB, a leaking check ball, or a sticking 3-2 control valve. It is not the B1 band, which applies in 2nd gear. Try doing a Transmission flush with a fiction modifier added to the oil ,it just may free the valves if not the accumulator piston could be crack.
Reply With Quote
  #8  
Old 04-14-2004, 07:06 AM
BlackBeauty's Avatar
BRABUS'ed
 
Join Date: Feb 2003
Location: South East Asia
Posts: 125
Quote:
Originally posted by C32AMG
chuck,
Post what you find, for future reference


Black beauty,

The cause of a Harsh 1 - 2 and 2-1shift, could be a sticking, 1 -2 accumulator piston in the VB, a leaking check ball, or a sticking 3-2 control valve. It is not the B1 band, which applies in 2nd gear. Try doing a Transmission flush with a fiction modifier added to the oil ,it just may free the valves if not the accumulator piston could be crack.
C32AMG, thanks for the tip. Been reading your advice on transmissions. You are an expert indeed.
Reply With Quote
  #9  
Old 02-05-2006, 02:51 AM
Brandon314159
Guest
 
Posts: n/a
I would like to bring this thread back to life becuase oddly enough...I even titled my thread over on diesel discussion very similarly!!!

722.3 Tranny...NO modulating pressure (measured at port) and good governed pressure.

Haven't tested working pressure yet.

Huge flares going into all gears yet drops into drive/reverse as before

Shift points are all the same

Have had the valve body apart...no pieces...no burnt fluid...nothing SEEMED broken.

Anyone know what I should be looking at?

Oh and I pulled the valve on the vac modulator already and it seemed to move smoothly in its bore...

Thanks!



EDIT: Already fixed the problem...check out the thread on diesel discussion if you want to read more

Last edited by Brandon314159; 02-05-2006 at 04:20 AM.
Reply With Quote
  #10  
Old 02-05-2006, 08:51 AM
C32AMG's Avatar
Registered User
 
Join Date: Mar 2004
Location: new york/orange county
Posts: 639
Modulation pressure is checked with NO vacuum line connected at around 31MPH, there
Should be no less then 40 PSI. Are you using the port next to the modulator and what color
Modulator do you have. We are taking about the 300SD.
Reply With Quote
  #11  
Old 02-05-2006, 09:34 AM
Brandon314159
Guest
 
Posts: n/a
Its already been fixed actually

Was a combination sticking valve in the valve body (which was fixed first) and then a misrouted vac hose causing problems.

Glad I didn't drop the pan and spend that whole day inspecting/cleaning/etc. the valve body for nothing!
Reply With Quote
  #12  
Old 02-05-2006, 10:41 AM
C32AMG's Avatar
Registered User
 
Join Date: Mar 2004
Location: new york/orange county
Posts: 639
I know exactly what you are saying; it would have been a good learning experience.
It takes a lot of time and patience on valves bodies which have stuck valves. Removing, cleaning
the valve and accumulator bores without damage can be a real PITA.

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 06:41 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2022, 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