w124 300D 2.5T (250DT) tranny swappability

[vlonb]

Hello!


I bought a '89 w124 250DT (300D 2.5T in America iirc?) two months ago.
These come with a OM602.962 along with a 722.418.
Transmission was replaced shortly before along with filter.

Last month my car stopped moving and went to neutral when going up a steep hill. Smelled like burnt atf, and that was the last I saw of my second gear.

My technical skill is limited, most of my knowledge is from researching on the Internet during the last month. Feel free to correct me if I say something strange.

Summary:

- Shortly before transmission failed a howling noise and loss of power appeared when in second gear under load (hills, heavy throttle). Got louder after a while, then ceased to appear shortly before transmission meltdown.

Now:
- Reverse & 1st gear works, upshifts at the usual (strange) rpm
- 2nd gear does not engage - goes to neutral (B1 piston/valve?)
- Stays in 1st gear if locked in any gear. ( when locked in 3rd gear it does not brake as much)

- Gear shifter sometimes refuses to go up to R and P, but can still move freely from N and downwards. Happens randomly, unstucking also seems to be random. (shift linkage bushing? Governor?)
- Odd shifting points and partial flaring (bowden cable and modulator adjustments needed)
- Clunk when downshifting to first gear - sounds kind of like hitting a loaded spring (Modulator adjustments?)
- Sluggish first gear at low speeds - delayed engagement of first gear from a standstill

Removed kickdown switch, no difference.

Did not open fluid pan yet (will probably find fragments there?)

Fluid is there, unknown condition. One month old

None of these faults were present when I bought the car apart from the odd shifting points.

I checked the tranny number, and I found out that the transmission on the car actually was a 722.414 - a 250D transmission.

1. Is the 250D transmission the source of my problems?
I'm not interested in changing parts on the transmission if it will be wrecked within another month of driving.

I've read a couple different opinions about using transmissions from other diesels - some say that it would work fine apart from slightly different shifting points. [

I called a MB auto specialist - he said that the transmission would be torn apart by the extra power of my engine.
Is this correct?
Isn't all of the 722.4 trannies W4A020, rated for 145 lb/ft or ~196nm?
Ref. Europeantransmissions application list

I'd really like to know whether it was the wrong tranny, or if it was the condition of the tranny.

2. What transmissions would fit for my vehicle?
As far as I know the .413 which belongs to the 190D 2.5T is a direct fit.
However the .413 and .418 transmissions are a nightmare to find in Norway.

The tested gearboxes avaible now are the following:

722.414 from '88 250TD and '93 250D
722.415 from a '92 300TD
722.434 from a '95 250D

Are there any problems with the newer gearboxes e.g electronic speedometer?

3. Would I be better off going to the more sturdy 722.3 from a 300DT?

4. Maybe a manual conversion would be better? I believe I have more options if I go down that road.


The engine runs just fine, gets 4̶5 40* MPG, car has ASD, doesn't have any dangerous rust and is road certified for almost two more years, so I think it would be worth throwing some money at.



Attached is a spreadsheet I made with the info available: