Help. Is it time for a transmission rebuild?

I'd like some help with an automatic transmission problem I'm having on my '83 300D turbo.
When starting from a dead stop in "D", it shifts from 1->2 OK (a little
harsh, but OK), then 2->3 flares badly, and finally 3->4 seems OK. The 4->3 downshift is a bit jerky too. The 2->3 flare is pretty bad under moderate accelleration -- the tranny disengages 2nd gear, then engine free wheels and revs up, until eventually the tranny engages. Under very gentle accel, or very heavy accel, there is no flare.
Once engaged in all four gears, the transmission doesn't seem to slip, which leads me to think there is just some internal adjustment out of whack instead of warn parts in there. Are there internal adjustments or parts shy of a complete rebuild that a good transmission mechanic can fix that might help?
thanks, patbob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You can try changing the servo piston... which is accessible from the side of the tranny. mbz.org has the info on this... Richard?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Research the B2 Piston, or is it the B2 Servo - same part whichever its name.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks. I looked into B2 over on mbz.org for now. Sounds like it affects mainly 1->2 shifts, which are not giving me any problems at any speed or throttle. However, that page recommends the K1 spring set, which sounds like it affects exactly the 2->3 flare I get. I'll look into both more tonight -- thanks much for the pointer!
BTW, I noticed in the B2 instructions on mbz.org that there's a similar cover next to to B2 one.. there isn't by any chance a B3 piston that can be broken, is there? I'm only asking because the described behavior with a broken B2 fits pretty closely, but for the wrong gear. A broken B3 piston (if there is such a thing) might be another possibility.
thanks, patbob
T.G. Lambach wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I don't know much beyond the B2.
When was the transmission fluid last changed??
If it was long ago or unknown I'd suggest changing the fluid and filter before opening the transmission. A change isn't expensive and may cure the flaring and so delay the inevitable a while longer.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Duh. One should always google things before asking stupid questions. Seems B3 exists, but is related to reverse.
As for fluid change, I don't know when it was last changed, so I was planning on doing that first. After all, pleasant suprises sometimes do happen. However, if the tranmission was already totally beyond any possibility of my repairing it, then I figured I wouldn't wait till I can get time and parts to do a fluid/filter change and just take it in and have it rebuilt.
The B2/K1 seem like good possbilities for me to research while I'm getting to the fluid/filter change.
thanks, patbob
T.G. Lambach wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

On my 300sd (same vintage) there was a vacuum modulator/switch mounted on the valve cover (as I recall it had three vacuum lines coming onto it). When that failed to function the transmission shifted late and (in addition to the throttle linkage being maladjusted) was late on downshifts especially. It felt like the car would get kicked in the arse as I was coming to a stop. It might be worth your while to check if that same arrangement in on your car as well.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It'd be the B1, not B3 piston and it was broke it wouldn't work nearly as well as yours is. Basically it would only go into gear with very very very little or no throttle and if yougive it too much throttle it'd pop back out. You have to ease up on the gas EVER SO SLOWLY but once it's shifted it'll stay in gear. It's a real joy to drive a car this way. Not.
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sounds like K1 spring to me. Maybe not but it'e cheap and easy to try.
B2 piston is 1-2 and 2-3 only.
Adjusting the vacuum is probably a good idea too, as is upgrading to the latest (revised; green, not black, vacuum modulator).
Adjustment articles:
    http://articles.mbz.org/transmission /
K1 spring replacement:
    http://articles.mbz.org/transmission/k1 /
This can be done withthe tranny in place on a 126 and JUST BARELY on a 127 and 107 while the tranny is in the car but I have heard of it being done.
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
[sorry for brevity, but have to respond quick before hte Toughbook CF-51 locks up or reboots again]
Richard Sexton wrote:

Ditto here. Fluid, filter & K1 are next thing to work on. Gonna crawl under there this weekend and get tranny model number so I'm sure I've got the right parts.

Found this and have already verified have updated modulator. Which is partly why I suspect tranny might not be original or expected model number (clearly, it's been worked on before).

Saw this.. pictures are not working. Anyone know where I might find them? I'm pretty visual and like to see pictures when I'm trying somethign new.

Mine's a 123, which sounds pretty doable with tranny in place from what I've read. Doesn't look like it cna happen this weekend though :-(
thanks, patbob

Aquaria? Knew the name sounded familiar from someplace :-)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yes the pictures have to be fixed. Theres also some articles on the site that dont work... I get a "404" when clicking them...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'm still trying to find the pictures. They're on a dead drive someplace.
If you wanna drop me a line as to what articles 404 I'll see what I can do about fixing them.
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.