Help. Is it time for a transmission rebuild?

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

patbob@imoveinc.com - 05 Oct 2006 07:46 GMT

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

Reply to this Message

Tiger - 05 Oct 2006 14:31 GMT

You can try changing the servo piston... which is accessible from the side
of the tranny. mbz.org has the info on this... Richard?

Reply to this Message

T.G. Lambach - 05 Oct 2006 16:53 GMT

Research the B2 Piston, or is it the B2 Servo - same part whichever its
name.

Reply to this Message

patbob@imoveinc.com - 05 Oct 2006 22:05 GMT

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

> Research the B2 Piston, or is it the B2 Servo - same part whichever its
> name.

Reply to this Message

T.G. Lambach - 05 Oct 2006 22:27 GMT

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.

Reply to this Message

patbob@imoveinc.com - 05 Oct 2006 23:41 GMT

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

> I don't know much beyond the B2.
>
[quoted text clipped - 4 lines]
> A change isn't expensive and may cure the flaring and so delay the
> inevitable a while longer.

Reply to this Message

me - 06 Oct 2006 02:46 GMT

> Duh. One should always google things before asking stupid
> questions.
[quoted text clipped - 26 lines]
>> A change isn't expensive and may cure the flaring and so delay the
>> inevitable a while longer.

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.

Reply to this Message

Richard Sexton - 06 Oct 2006 06:37 GMT

>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.

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.

Signature

Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
1970 280SE, 72 280SE | Home pages: http://rs79.vrx.net
633CSi 250SE/C 300SD | http://aquaria.net http://killi.net

Reply to this Message

Richard Sexton - 06 Oct 2006 06:35 GMT

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.

Signature

Reply to this Message

patbob@imoveinc.com - 06 Oct 2006 21:35 GMT

[sorry for brevity, but have to respond quick before hte Toughbook
CF-51 locks up or reboots again]

> Sounds like K1 spring to me. Maybe not but it'e cheap and easy to
> try.

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.

> 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).
> http://articles.mbz.org/transmission/

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).

> K1 spring replacement:
> http://articles.mbz.org/transmission/k1/

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.

> 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.

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

> --
> Need Mercedes parts? http://parts.mbz.org
> Richard Sexton | Mercedes stuff: http://mbz.org
> 1970 280SE, 72 280SE | Home pages: http://rs79.vrx.net
> 633CSi 250SE/C 300SD | http://aquaria.net http://killi.net

Aquaria? Knew the name sounded familiar from someplace :-)

Reply to this Message

Steve Jensen - 08 Oct 2006 06:48 GMT

Yes the pictures have to be fixed. There´s also some articles on the site
that don´t work... I get a "404" when clicking them...

Reply to this Message

Richard Sexton - 09 Oct 2006 03:49 GMT

>Yes the pictures have to be fixed. There´s also some articles on the site
>that don´t work... I get a "404" when clicking them...

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.

Signature

Reply to this Message