W123 300D 1984 automatic gearbox

[chorse]

Dear All,

I have just purchased my Merc 300D auto 1984. It is absolutely magninficent apart from some gearbox issues.

I have to really rev the engine to get it into 2nd. In order to do this I have to take the car upto a certain speed and then layoff the accelerator completely whilst it changes up (quite roughly at that, it jolts).

This is also applicable for third. Once I reach 54 mph and then layoff the accelerator completely it changes up (smoothly this time).

What do you think this is? Will it be expensive?

Also does this age of car have an overdrive or is three gears all I can expect? I am tring to locate a manual.

 

[Matt Crooke]

Hi there

judging by the age of the car (my 190 was only 3 years younger) you will have 4 speeds, however it only feels like 3 because the box defaults to second gear pullaway all the time. A quick way to test is when you are statinary in D, pull the lever back to 2, then push forward to D. This will force a first gear start. Also if you accelrate hard (or floor it) from a stand still it it will again force a first gear start.

You will quickly notice that 1st is exceptionally low geared, hence its hardly ever used.

again my 190 did seem to change rather funny, however if you use a light throttle from standstill, it should (all being well) slip through the gears nicely.

Let us know how it goes.

cheers

 

[chorse]

Crap gearbox

Even when I treat the accelerator pedal very gently, it still doesn't change up.
What could cause this? Someone mentioned a solenoid on the gearbox

Cheers

Jason.

 

[thekeeper24]

my 1981 300D (W123, Engne 617) is similar,
you usually never notice 1st gear from normal to semi-hard accelleration. ive found that second and four are used the most. even under a moderate accell, secoond will take hard then a short third to fourth. i dont believe fourth is an OD b/c the max speed for third is somewhere between 50-65mph (check the speedo for little orange marks) and its goes beyound that speed in 4th. Step on the gas from a complete stop; you will undoubtly feel and hear the 1-2 shift.... best of luck

 

[chorse]

Thanks

Thanks for the reply all. I'm still adamant that my gear changes are not functioning adequately. Even if I drive really slowly upto 30 mph my engine is screaming. The only way to change up is by letting my foot completely off the accelerator.

When I am going downhill at 45 mph with my foot off the accelerator you would expect it to change up to the highest gear. Unfortunately the engine is still screaming.

I hope someone knows what the remedy will be short of a gearbox overhaul.

All the best

Jason.

 

[Chopper773]

Hi

Another newbie with a 300D albeit a lot older and American. I know this is a daft question but have you checked the condition of the fluid? I don't know about the Merc but my old Rover (GM box) would misbehave if the fluid was old or low.

Hope this helps

 

[chorse]

I'll check this out. I'm not very mechanically minded but I will find out where it is, drain and replace. I'll let you know. Thanks

 

[Chopper773]

On mine the dipstick for the box is between the air filter and the bulkhead. The fuid should be red, clean and not smell burnt. If it is dirty find a Haynes and replace the fluid and any filters in the system. If it smells burnt then you will probably need it rebuilt.

 

[chorse]

Thanks for your help.

I'll let you know.
By the way, does your car have a small dial/knob next to the dashboard keyhole. I belive this is some sort of choke. Which way to turn the choke on. I currently have to keep my foot on the accelerator to keep at gentle tickover whilst at a standstill until the engine has warmed up.

I've ordered a manual but it's not arrived yet.

Cheers

Jason.

 

[thekeeper24]

there a small knob to the left side of the steering colum (the igintion is on the other side) which is used for the idle adjustment, i believe counter-clockwise is to increase the idle, you should press the accel when you turn the knob. mine was broke since i got the car thou. it is an american w123 enigine 617 1981 300D.. good to know there's another 300D on here

 

[Andy]

Hi All

The gearbox will change smoother with less aceleration. As then there is enough vacuum make a difference to the modulating pressure. When flat out all the vacuum is exhausted. There is a box on the side of the pump if miss adjusted or just knackered will cause rough changes. You should also check the control pressure cable length to make sure the gear box changes as and when it should do. It won't change up under full throttle. If as you say you have minimum experience. I would suggest you get it into your local specialist or get a manual and study how it works. Then you should get to work satisfactorily. I doubt changing the gearbox oil will have any significant effect.


Regards & good luck.


Andy @ www.mercedesservicing.com

 

[chorse]

Thanks for all your tips. I got a guy to fiddle around with the vacuum pump. Apparently it is also linked to central locking vacuum?. It now changes very smoothly with the min. of effort.

What a dream!

 

[Jimmer]

1981 200t in malawi, similar problem...

Hi,

Very interested to read this thread. I have a 1981 200t, and have a similar problem, i know there is a problem with the vacuum as my central locking works either only half way or not at all.

I also have a fairly sticky gear change, like you say, sometimes it just keeps revving in 2nd until i lift my foot off the accelerator when it finally changes up - 3-4th not a problem though.

Can you give me any idea of what this chap did to your vacuum pump? and whether any parts were needed?

I am currently living in malawi, mercedes specialists are rare in this part of the world so any advice would be greatly appreciated.

Thanks, Jim

 

[chorse]

Apparently, there is a maximum you can turn this to before the gearbox starts slipping. As far as I can gather, there is a screw setting that you keep turning. Don't ask me where. Try looking in a Haynes manual. Mine still hasn't arrived.

Also look for any haemorrhaging of the pipework inside the door to the central locking. Sorry I cannot be more helpful but the guy told me I was paying fifty quid for his knowledge. He didn't wish to divulge what or where the thing was that he had tweaked.

 

[joe bloggs]

if the above does not cure then you will need to replace the teflon seals inside the box, not too difficult, no special tools required, but the box has to come out. These seals wear over time, oil seeps past them so the pressure applied to the clutch mech. is less, therfore box does'nt like to change gear until you ease up on the power.