locating perfect shifter rod length
 

i read that some hard (manual) shifting can be caused by a shift rod of slightly wrong length. i have hard shifting into 2nd and always blamed it on a worn synchro, but now i wonder if the rod length is also to blame. would this problem be associated with the 2-4 rod being too long or too short? is there any way to get the adjustment right the first time?

Before you consider it possibly the wrong length..
have you used the FSM instructions for setting it correctly ?

What fluid are you using for lubrication ?

oh dear, i wasn't aware it was in the FSM. thanks for this. just took a look and i couldn't find it. do you have a chapter number?

as to the fluid - i believe i have ATF in there, and am expecting to switch to something a bit more viscous. i have synthetic in hand for this but could not loosen the trans fill plug when i was under the car.

It has been suggested by JimSmith, moderator, that some fluids might erode the synchro ... somewhere in the archives he talks about that...
So I suggest that you use, based on what he said he recommends , ( which I changed to also ) Redline MTF...
Do not try to go with more viscous fluid... stick to the factory recommended thickness...
I do not have a chapter off hand... but I am sure it exists... typically it will involve a pin being placed into several things .. then you adjust the lengths of the other things which connect to it... it is very easy once you see the directions.. pretty much fool proof... so since you have been far enough to touch the plugs.. should not be a problem..
Before letting the fluid out... be sure you can loosen the fill plug...

edit.. the close fitting locating pin is typically a commonly available drill bit.. the back end...

EDIT... ok at one AM in the morning , visualizing lots of auto trans red thin fluids I wrote Redline ATF instead of Redline MTF.... M for manual transmission... I realized this after I went to bed...

When you say hard shifting do you mean it crunches?

I think if the rods are extremely maladjusted it can cause hitting two gears at once or could cause the gear not to be fully engaged and popping out when the clutch is released.

bricktron:

Is the gearbox iron?, or aluminum? 4-speed?, or five?
Does "hard" shifting mean additional force is required to push the lever into 2nd?, or does it mean what Tom asked: crunching?

Her is a picture of the pin, drill bit etc.... to line up the shift levers of the shifter.
It is of a 5-spd shifter but the alignment is the same.

That has to be lined up first before adjusting the shift rods to the transmission.

The levers on the transmission all have to be in neutral.

Also make sure the bushings are in good shape or just replace them while you are in there.

Iam using synthetic ATF in my old iron box trans in the 80 240D w/o any problems.

When I swapped on the aluminum box 4-spd in the 85 300D, I first tried to use synthetic gear oil.
It is too thick even as thin as it looks to shift properly. I use it in my Datsun 5-spd and works great, but the MB is different.

So changing it to the synthetic ATF, all is well.



http://www.peachparts.com/shopforum/...-positions.jpg



Charlie

If this is a manual transmission or maybe even a auto Stretch has the German Mercedes Service Manual and claims it has the transmission stuff. He could be someone to ask.

thanks everyone, especially charlie for the citation. i have read about this pin-locking trick before but did not realize it could be used for adjusting shift rods.

this is an iron box 4-speed. when i said "hard", i meant both that it is a bit difficult to get into 2nd, and that getting into 2nd too quickly causes crunches (double engagement?). the threshhold for that seems to be about a second, so for 0-60, i am tempted to redline 1st and skip right to 3rd, or else start from 2nd, to avoid the shift latency. i don't know if it could reasonably be any faster, but i would love to stop grinding the gears when i get too enthusiastic.

is there any evidence that changing manual transmission fluid can affect shifting behavior? (past wear seems like water under the bridge at this point.)

b:

The description of shift characteristics is consistent with the iron box 1-2 shift when the trans is, uh, "experienced". The ratio spread between 1st and 2nd is greater than for 2-3, or 3-4, and as a consequence, the synchronizer receives more wear than on the other shifts. Sorry to say, it is in the expected category.

Some improvement can be made by: 1) ensuring that the clutch is not dragging when released, 2) using a double clutch "pause" to allow the engine speed and the clutch disc speed to drop further during the 1-2 shift, 3) using only petroleum based ATF in the trans, 4) if you can find some, using Type F ATF (Type F lacks the friction modifiers found in Dexron, and as a result allows the synchros to be "grabbier". B&M Trick-Shift ATF is essentially Type F.)

By ' changing trans fluid ' affecting shifting behavior I am assuming you are asking if changing the viscosity of the fluid you are using... based on you saying you are thinking about ' something more viscous' ...
Yes... viscosity makes a difference but I am not going to provide url references... the FSM recommends certain fluids and they have done all sorts of long range ( time wise ) testing on these things...but if you do not trust the FSM then you will not likely trust me saying that....
However, being old, I remember when Chrysler (?) changed their manufacturing tolerances and thus their trans fluid recommendations ' back in the good old days' and people who did not believe their newer and thinner recommendation actually had the trans catch on fire.... LOL

interesting to see the rapid consensus that shifter rod length is not a factor.

[QUOTE=Frank Reiner;3623938]
The description of shift characteristics is consistent with the iron box 1-2 shift when the trans is, uh, "experienced"./QUOTE]

thanks frank for this useful post. short of rebuilding the thing (i have a spare iron box to work on, thanks to DeliveryValve), i will see about the trick-shift ATF. hopefully it will not catch on fire, leathermang!

Absolutely

I'll try and find the link.

Use ATF as specified by MB and it'll work - other stuff is likely to cause shifting trouble