Erratic gearchange w124 e300d

[stigsblade]

Hi Folks

I am planning a long drive and would like to resolve a gearbox issue before I go. Gearchange is not as smooth as it used to be, particularly 2nd to 3rd, where it seems to get "Hooked" and wont go to 3rd. When it does change, there is quite a jolt. other changes are quite good as long as there is not too much torque. Strangely, everything seems almost normal when the engine is cold. I have had something similar to this in the past and resolved it by finding vacuum pipes disconnected, but these seem ok this time. I recently had the cylinder head off but have not changed any of the throttle linkage settings, however could the engine be more powerful?

 

[momomo]

I think if its not the vacuum pipes it will be the gearbox il level. It will be low and will need to topped up to the right level.

It you havent changed/serviced the gearbox oil before it would a good idea to do so.

 

[Number_Cruncher]

As the head has been off, the control pressure cable (sometimes called bowden cable, or kickdown cable) will have been disturbed. The bracket for this cable doesn't locate particularly accurately in the cam cover.

I would check the routing of the cable, check the cable runs freely, and check its adjustment.

 

[stigsblade]

Have checked gb oil-ok (changed 20k miles ago) bowden cable seems ok have adjusted about 1/4 inch less thread and has not seemed to change anything, will now try more thread showing.

 

[Number_Cruncher]

If you can change the cable by 1/4 inch and nothing changes, something is wrong - the cable is usually *very* sensitive, even to small changes. Is the cable routing OK? - does the cable run freely in its outer tube?

 

[stigsblade]

AARGH!!! the thing has just died on me! Just cut out! 5 days before France and I think it could be fuel pump, turns over fine but wont start. Just testing lift pump fuel delivery.

 

[stigsblade]

ok all is ok again, must have had an airlock

 

[stigsblade]

Perfect gearchange now, bowden cable was trapped under crossover pipe, and I'm guessing as it expanded it increased pressure on cable, explaining why it was ok when cold. Thanks once again NC, you're a bit of an expert it seems! I have another post regarding power steering pump, any clues? I hope I can be of help to you some time, I'm keeping this car for the forseeable.

 

[stigsblade]

Update; problem seems to have returned. Seems to have something to do with higher revs/power and mainly to do with 2nd to third. Seems intermittent, maybe to do with temp? How do you adjust bowden cable or throttle for best performance?

 

[stigsblade]

update;
problem has returned, a little better but still quite bad on 2nd to 3rd. Seems fine when warming up. Is there anyway I can check vacuum pressure? how do you set bowden cable accurately? Any other ideas?

 

[Number_Cruncher]

The official way is to detach the end of the bowden cable, and pull the cable out until you feel slight resistance. At this point, the cable end should be directly opposite the ball it fits onto. If not, adjust the bowden cable to suit.

I think the above gives a good starting point.

What I then do is, with a thoroughly warmed engine drive the car along a flat road, and with the throttle fully depressed, kickdown activated, see when the car changes up. Ideally, it should be at the points marked by dots on the periphery of the speedo. I tend to adjust mine to be changing up just before then.

If the cable is running freely, you'll find this last part of the adjustment is quite sensitive. Half a turn of the adjuster makes quite a difference.

I would check all of the vacuum system in the engine bay for leaks - as leaks anywhere can upset the vacuum level at the modulator valve. Have you got a vacuum gauge?

 

[stigsblade]

No I havent but will try to get one for next week when I am back. What settings will I be after?