What controls Full Throttle/Kickdown on M104?
 

I am baffled by the inability of my 93-300e2.8 to hit redline in any gear.

Here are my observed shift points with lever in "D"

shift WOT Kickdown
1-2 3.8k rpm 4.2k rpm
2-3 3.8k rpm 4.2k rpm
3-4 4k rpm 4.8k rpm

With lever in "2'" + kickdown produces 1-2 shift with the highest rpm at 5.2k.

I have adjusted the bowden cable which moves the shifts points at less than but not at WOT or Kickdown. Is this symptomatic of a vacuum leak? What else would prevent the tranny from shifting at or near redline?

It does sound like the bowden cable or even the throttle cable is out of adjustment or stretched.

make sure all valve body mounting bolts are properly tightened,if bolts are ok there is a small allen head adjustment on the right front of the valve body.
turn this screw out,but don't start with large adjustments maybe 1/4 turn at a time.if you go too far the r.p.m. limiter come into play.
these adjustment should only be performed after checking condition of cable and it's adjustment.
m.f.

Benzmac,

Both the throttle and bowden had a lot of slack. I've tightened the throttle to max with no effect. When I adjust the bowden it just moves the shift points at part throttle.

Mike,

I'm not sure about where the valve body/screw is. Was just under there looking but not sure what part of the tranny it's in. Where exactly is it? I have the CD manuals for W124 is there a section that describes this?

I have always suspected that the car may have been "de-tuned to protect grandma" as she drove around town...

JSmith (what is your first name anyway?!),

Did you ever find out what was wrong? Now, it was hitting redline BEFORE you (/we ;) ) started making Bowden cable adjustments? And after fooling with the Bowden cable, the redline changed? :confused:

Hmm, I'd be stumped too. No matter the adjustments I've made, I am still able to hit redline... WOT and kick-down haven't changed a bit.
GOOD LUCK and let me know what's going on. :eek: :rolleyes:

david,

no, it has never reached redline and none of the adjustments we have made with the bowden cable changed the max rpm's. making the shifts later actually fixed my harsh shifting but the shift points only changed at part throttle as you may also have observed since you still hit redline no matter what.

while we were under there my mech was trying to snap off the modulator cap. i knowingly said that, no that just adjusted the shift feel and not the max rpm and i didn't want him to break the cap off;).

i may have to go and get that MB tranny manual i saw in one of the threads just to figure out what mike is talking about.

joe

Joe Smith (Isn't that original?! ;) ),
The problem must be elsewhere?? I don't know. Hopefully the techs will help you out with this one.
GOOD LUCK!

thanks, david and no i ain't from utah (someone actually asked me that once).

BTW, has anyone picked up a manual from this place:

http://www.atsgmiami.com/cart/Category.Cfm?Cat=36

Do they have blown up pictures etc.?

Its especially strange that kickdown doesn't change the shift point much. I would verify that power is available at the kickdown switch (terminals 1 and 2 should be hot without closing the switch). Power comes from the A/C compressor control module (strange as that might seem).

If you get internal, you should verify that the control pressure piston goes full travel when someone floors the throttle. If it does reach full throttle, loosen and retorque the valve body and as Mike said, adjusting the allen screw will change the shift point, about 5mph per turn.

I have seen a couple 300SDLs that exhibited absolutely low shifting. Such that no external adjustments mattered. I fixed both with a valve body. MB provides rebuilt valve bodies so cheap, for most units, that very few techs have ever learned enough to fix them properly. One of those people visited this site for a time from Australia (where they can't buy rebuilt VBs). Another is Mario Arisides in Miami. I wouldn't be surprised if that link above gets you very close to Mario. He has consulted on most ATSG MB projects, (I hear). His business is called Independent Transmission.

ahhh, thanks Steve! i have been trying to figure out how to test the kickdown circuit. i have tested the switch itself and it appears operational with one pair constant on and the other constant off.

while my local indy is very good, he is really a trained BMW tech not MB. knows quite a bit about benzes and doesn't mind that i do a lot of research prior to coming over. that book may come in handy after all...

an update:

i have been tracking down leaks in the tranny the past month and found that fluid lines on both sides were leaking. it seems that the seals that were in place were the wrong size and were barely keeping the fluid in. what surprised me was that now it kicks down all the way to second (never did that before) at around 50-60mph and it is shifting quite a bit higher than before at WOT. still not at redline but a marked improvement. i have yet to make careful observations on the new shift patterns. could new tranny fluid have helped - i have about 2k miles with the new fluid. did those leaks have anything to do with the problem?

i'm still having it checked out but this was a surprise...