[Mahone Bay]

Hello All,

I'm looking for feedback on what one can expect as to the shift quality in a 300SD with a 722.303 automatic.

My car is a 1981 version with 120,000 km (75,000 mi). I know it sounds low but they are legit based on the service history and the general condition of the vehicle. My assumption is that the general condition of the gearbox is good but having been driven so little some deterioration will have taken place. So I decided to be proactive.

I have replaced the following in my gearbox;
1. B1 Servo
2. B1 Valve
3. K1 Valve
4. B2 Servo
5. Kick Down Solenoid (new style)
6. Vacuum Modulator (new style)
7. Filter and fluid.

All are MB components. In addition I have adjusted the modulator pressure as we as the vacuum to the modulator - all to the latest MB specs.

I still find the changes under normal acceleration from 1-2 and 2-3 too noticeable. The 3-4 shift is barely noticeable. I was expecting barely noticeable shifts for all changes but maybe I am expecting too much.

As a last resort I'm considering one of those after market shift kits;

Transmission Part by Bulk Part Valve body kits Shift correction package, 722.3 / 722.4 Diesel

Anyone tried one of these kits?

Any thoughts / feedback?

Thank you and take care,
PK

 

[liammarsh]

I've had three different transmissions in my 300SD now so I feel like I had a good breath of shifting problems. Transmission with 75K on it should be good. I am assuming that after all the work you did on it there was no change in how it shifts?

Assuming you played around with the shift cable tension?

I have not experienced with the valve body kit you are speaking of though I messed around with swapping out valve bodies on one of my transmissions.

Does the shift quality in those two shifts points change when you change the acceleration - slow or fast? I think that you definitely can have smooth shifting at all points with this car. (I almost do).

It it good to remember that for the transmission to shifts properly the engine has to be working properly. If you have engine performance issues, you will have shifting issues. It is all design to work in a delicate balance. I had a ALDA line that would come off resulting in no turbo. Every time that happened I would experience it as a transmission shift issue because it started shifting different. So a rough shift can be the results of not enough horsepower but the transmission is fine.

Sounds like you know what you are doing so you could try the valve body kit and see what happens though I think it is just a shot in the dark.

This book was helpful for me though I started without much car mechanic experience:

https://mercedessource.com/store/di...n-peak-performance-tuning-manual-kent-bergsma

Good luck!

Bill

 

[liammarsh]

Here are some valve body diagrams. (You may have all this stuff - posting it for others if needed)

 

[Mahone Bay]

Hello Bill,

Thanks for the feedback and the PDF. I will add the latter to my reference file.

Your feedback has good merit. Prior to the gearbox repairs I adjusted the valves, adjusted the throttle linkage, adjusted the shift cable, rebuilt the injectors with new nozzles and adjusted the injectors to open at 1950 psi. ALDA has never been touched and all the vacuum hoses have been replaced. I also checked the turbo boost and it is where I would expect it to be under heavy load ~10 psi. Having said that I do have all the bits to rebuild the turbo as it has a bit of play in the bearings. This will probably be my January project.

The only thing I haven't touched as yet is the injection timing and this is being done as you read this. The gasket between the IP and the front housing was sweating a bit of oil (I hate engines the leak fluids), so this was an excuse to replace the gasket and adjust the timing. I don't expect this to make a huge difference.

Coming back to your comment about the shift cable - I will be playing around with this again as the current adjustment was based on the gearbox before the upgrade (B1 and B2 servos) done last week.

If you have any other thoughts - let me know. In the meantime I'll keep testing and playing detective. If I discover anything I'll update this thread.

Thanks again and take care,
PK

 

[DreamMachine]

Resurrecting an old thread here.

Any updates on your transmission issues?

I recently purchased a 1983 300SD with 107k miles on it and am having some trans issues.

I am curious if you ever solved the problems you were having.

Thanks,
DreamMachine