Mercedes-Benz Forum banner

1 - 20 of 21 Posts

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #1
Hope someone could help.

I have a pre 1980, im not sure when it was produced, w123 300d with an automatic transmission. I think it's a 722.1. I'm confused if it's 3 or 4 speed coz I can only feel up to third gear. It also shifts from 1st to 2nd at around 38 kms per hour. I think this is a little bit late. I read somewhere that the modulator is the only way to adjust the shift points. Can someone post shift points for my model.

TIA
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
Your pre-1980 model does not have vacuum control or a vacuum modulator. It is a four-speed transmission, but it starts in second gear, unless you use kickdown or L.

The transmission is controlled by a control rod connected to the throttle linkage. Adjustments should be done according to the book, otherwise damage to the transmission might occur.

(Where are you located? Is it a euro-W123?)
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #3
I'm from the Philippines and it's a Japan unit.
You're right it doesn't have a vac line. I'll check underneath if it has a modulator.
Saw this on how to adjust 722.1 trans 722.118 Transmission Adjustments
Or I could be wrong.
Shifting from the first, or as you say second gear, to the next takes up to 38km/hr. Is this normal? I think this may be the cause for high fuel consumption.

Thanks
 

·
Registered
1981 300D with a funny tranny
Joined
·
965 Posts
I own a 1980 300D with a 722.122 or 118 tranny. It was shifting weird flaring between 2-3, I did a lot of stuff I read online and spent a lot of money changing stuff that didn't need to be changed. I took it to 3 specialized shops and all wanted from 3-4 thousand to fix it.
I decided to sell the car out of frustration, but not without giving it a last chance: I bought a transmission diagnose kit from Mercedes Source. This allowed me to understand and decided what really needed to be done, and also realize how those shops wanted my money. I recommend you to do the same, it will save you tons of money due to all the small repairs you learn to do yourself for the future.
This is the diagnose kit: 123 126 Diesel Transmission Ultimate Diagnostic and Tuning Kit | MercedesSource.com

For now I can tell you that if the engine is not functioning properly (meaning power, injection and timing) your tranny will do bananas.

-Start with a diesel purge and change fuel filters.

-Oil change, oil and air filter.

-replace all leaking fuel hoses, like the ones in the injectors.

PS. Try to do the most yourself is easy and fun. =)
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #5
I already did change the trans filter and fluid. Checked all the hoses and other stuff. Everything's seems to be fine. I don't have flaring or slipping issues just want it to shift up to 4th if it's a 4 speed and at a lower km/hr to save on fuel. It would be a big help if my unit came with an rpm but I guess some models doesnt have it. I would also appreciate it if someone could post the shifting Sched so that I would know it this is normal.

I checked this morning on a hot engine, I start with the first gear not on second. I only feel 3 gears. 1-2 @ 38km/hr, 2-3 at 50km/hr
 

·
Registered
1981 300D with a funny tranny
Joined
·
965 Posts
I already did change the trans filter and fluid. Checked all the hoses and other stuff. Everything's seems to be fine. I don't have flaring or slipping issues just want it to shift up to 4th if it's a 4 speed and at a lower km/hr to save on fuel. It would be a big help if my unit came with an rpm but I guess some models doesnt have it. I would also appreciate it if someone could post the shifting Sched so that I would know it this is normal.

I checked this morning on a hot engine, I start with the first gear not on second. I only feel 3 gears. 1-2 @ 38km/hr, 2-3 at 50km/hr
Well... when I'm above 55mph it feels like I could use another gear too. :D The first gear is extremely short and some people say that the cars start in 2nd. However if there is something to do is a diesel purge and oil change. What is the other stuff you say you did?
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
I already did change the trans filter and fluid. Checked all the hoses and other stuff. Everything's seems to be fine. I don't have flaring or slipping issues just want it to shift up to 4th if it's a 4 speed and at a lower km/hr to save on fuel. It would be a big help if my unit came with an rpm but I guess some models doesnt have it. I would also appreciate it if someone could post the shifting Sched so that I would know it this is normal.

I checked this morning on a hot engine, I start with the first gear not on second. I only feel 3 gears. 1-2 @ 38km/hr, 2-3 at 50km/hr
It is shifting to 4th gear, it starts in second gear, shifts to 3 at 38 km/h and to 4 at 50 km/h. Try shifting it to S (3rd gear) at 80 km/h, you will hear it shifting back to 3.

I will have a look at the correct shifting speeds in the FSM this weekend.

For adjustment to the control rod and accelerator linkage, have a look at the FSM:
30 Accelerator Control - OM617
select the correct model under 30-300.1

Diesel purges, fuel filter changes etc. don't change the shifting behaviour.
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #8
Did purge, engine and trans oil and filter change, changed fuel lines even if not leaking but hard already, valve and chain adjust, replaced front bearings, reface rotor disks, replaced worn out suspension parts and bushings, replaced compressor evaporator drier and expension valve, recharge r12 freon, replaced coolant, replaced ps oil and filter, air cleaner and coolant too.
Most items are not related to the tranny but I want to keep the unit so I try my best to keep her happy.
Nevertheless shifting still starts at 1st then changes only when it reaches 38kms/hr. Maybe it's a little late so I couldnt feel the 4th coz it may come at 100kms/hr.
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #9

·
Registered
1981 300D with a funny tranny
Joined
·
965 Posts
It sounds like you have done all the good stuff, next will be to adjust valves and check for tension in the chain, if it's stretched it will be good to change it cuz it affects the overall timing. Said that injection pump timing needs to be checked too. I have read that compression test is needed before doing anything, if compression is bad you will probably have worn rings or valve issues. And overhauling and engine is $eriou$ work.
There is a couple of authors that have books about the subject (like Kent Bergsma) and they point to a malfunctioning engine as the most common cause of poor shifting. Most common neglected items are filters.
In my case, after spending a ton of money in random parts after following advice from the web, I did a diesel purge and renewed all filter and hoses (even though they were 2 months old) the tranny shifted a lot better. Now if you already did all of that, you may be looking at linkage, hydraulic pressure and then adjust the vacuum control valve to that.
A good thing to do is to poor new AFT in a glass container and then compare with what comes out of your tranny, take pics and a sniff and post it. If burned there is a couple of reasons, but the most common one could be bad news. Check for little metal particles, it's kind of normal but it depends of the context.

I'm pulling this info out of books and 1 car so I'm not your Messiahs. I advice you again to check mercedes source books they have a lot of valuable info I didn't find anywhere in the web for free.
(Though i found a lot of valuable info for free that was not in their books:D)

Yesterday, I successfully adjusted the VCV to the tranny, there is a way to do it but you need to have a gauge connected to the top of this valve and then write down all the little movement you do. I found I could adjust with this the shifting time but It made the first shift kick like a mule when the others started too early.

Can you take a picture or a video of your engine vacuum system?
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #11
did the valve adjust and chain already. injection pump and nozzles done too. transr and engine oil and filters just recently replaced. probably its the modulator. ill do this next week
 

·
Registered
1981 300D with a funny tranny
Joined
·
965 Posts
did the valve adjust and chain already. injection pump and nozzles done too. transr and engine oil and filters just recently replaced. probably its the modulator. ill do this next week
So, it has a modulator? I thought I read that it didn't.
please send pictures of the engine and the tranny pan from both sides of the car.(specially where the modulator is) If you could use some brake cleaner to make them more clear will be awesome. I have some guides of how to adjust earlier trannies but I have not done it yet.

Do you have this in top of your fuel pump? its called VCV.
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #13
According to the site I postedand performanceproducts4benz.com it should have a red colored modulator without a vacuum attached to it. Shifting is adjusted thru the modulator. I forgot to inspect it though.

My injection pump is different. The top is flat and nothing is attached to it except for the shut off valve which is on the rear of the ip
 

·
Registered
1981 300D with a funny tranny
Joined
·
965 Posts
According to the site I postedand performanceproducts4benz.com it should have a red colored modulator without a vacuum attached to it. Shifting is adjusted thru the modulator. I forgot to inspect it though.

My injection pump is different. The top is flat and nothing is attached to it except for the shut off valve which is on the rear of the ip
Good, so then make sure of the kind you have, there should be a code for your tranny in either side of the pan. I have read that is better to change it for a new one and set up the hydraulic pressure to specs to have a fresh start.

Again, mercedes source has them all and they have a modulator adjustment kit that comes with a gouge you can temporarily mount in your dash. I also read that early 722 trannies need to be adjusted after road tests.

take a look at this, and email them for guidance in which one is yours:
Search the Store | MercedesSource.com

I wish you good luck and I hope you decide to get the modulator adjusting kit:
61x Diesel Automatic Transmission Modulating Pressure Test Kit | MercedesSource.com
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
According to the site I postedand performanceproducts4benz.com it should have a red colored modulator without a vacuum attached to it. Shifting is adjusted thru the modulator. I forgot to inspect it though.

My injection pump is different. The top is flat and nothing is attached to it except for the shut off valve which is on the rear of the ip
The shift quality isn't adjusted through the modulator, not on a pre-1980 model.



the shift points are as follows:



Leergas is when the accelerator pedal is pressed only slightly.
Vollgas is the accelerator pedal fully pressed
Übergas is kickdown.
Speeds are in km/h
You can see that the first gear is only used with kickdown and in L.
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #16
Thanks 1980-300d and Govert. Seems like mine shifts a little late. I'll review the sites you gave and post the results If I can change my shifting.
 

·
Registered
2001 Volvo V40
Joined
·
2,954 Posts
Don't forget the speedometer usually indicates a higher speed than you are actually driving. If you have a GPS, you can check the difference between real and speedometer speed.
 

·
Registered
1981 300D with a funny tranny
Joined
·
965 Posts
The shift quality isn't adjusted through the modulator, not on a pre-1980 model.



the shift points are as follows:



Leergas is when the accelerator pedal is pressed only slightly.
Vollgas is the accelerator pedal fully pressed
Übergas is kickdown.
Speeds are in km/h
You can see that the first gear is only used with kickdown and in L.
GeeeZ!!! This is awesome info!:eek:
thank you!!:bowdown:
 

·
Registered
1978 W123 300D, 1986 S124 250TD, 1987 W124 300D-T, 1965 W108 250SE, 114 280C, W126 300SDL,W123 300CD
Joined
·
83 Posts
Discussion Starter #20
Adjusted my friend's 78 123 300d based your diagrams. We were having the same problem.
Though not exactly the same as what you've posted but the shift schedules are far more better than before.
I'm still waiting for my 123 to have the repainting finished and it will be next to have the transmission adjusted.

Thanks very much guys
 
1 - 20 of 21 Posts
Top