W124 autom. tranny
 

Greetings,
concerned how much life is left in my autom. transmission of my 91 300D 2.5T.
The original unit - 722.418 is still in the car - current mileage 136K.
Can buy a used one fm an 87 300D sedan for $ 200.- - mileage unknown.
Prior to installing would have it checked out/overhauled by a tranny shop.
Intend to keep this car for a few more years and therefore wondering whether this a good way to go.
Will the tranny out of the 87 300D fit and work correctly in the W124.128?
Has anybody done this change?
Thanks for your help.
PS searched the Forum but could not finds answers

Not many miles on your car what makes you think you need another transmission? Are you having issues currently?

That would be extremely low miles for a 722.4 to have problems. What's the history of fluid and filter changes?

W124.128 tranny
 

Many thanks for your responses. I am the third owner of this car and have complete service records. I have to say that PO drove the car rersponsible. First owner had the car 15 years. The tranny fluid was changed at regular intervals and at present I have Amsol ATF in there.
I know MB trannies don't shift as smoothly as the ones from newer cars but feel the one in my car is slowly getting worse. Still shifts without delay from P to R or N and I take this as a good sign. I am the only who is driving this car and most of the time I am not in a rush anymore. Will assume, tranny will last quite a bit longer. Cheers

If it's shifting too firm, start checking rubber vacuum fittings under the hood. As these age and crack they leak and low vacuum is known to cause firm/abrupt shifts. If the rubber vacuum fittings look spongey, feel soft, or look alligatored, plan on replacing them.

Automatics with problems tend to have mushy shifts, flares between gears, noises, delays, dropping out of gear, and other symptoms, not usually firm shifts.

I've always found hard/abrupt shifts to be vacuum related.

One thing you might want to pursue is simplifying the vacuum system: first by converting to a pressure wastegate, thereby eliminating all the vacuum stuff on the passenger side; then by other odds and ends.

True, harsh shifts are often vacuum, but in your car also ALDA or boost/wastegate. If the car isn't producing the power that it is supposed to, the transmission does not know it and adjusts the shift to where the pedal is, ... which results in harsh upshifts.

thanks for the advice - will check the vacuum lines when the car is on the hoist again

First off, your transmission has very low mileage. My 190DT, which has almost exactly the same drivetrain, made 320K miles before the transmission gave out. I wouldn't "simplify" the vacuum system, it's all there for a purpose and it all works with simple maintenance. Nor is it an Alda or wastegate problem, that's just pure nonsense. But yes, a vacuum leak somewhere can cause shift problems, so it's worth going through the vacuum system with a Mityvac. If the shifting is firm in all gears, backing off the modulator a bit may be all that's needed. Do this using a pressure gauge following the factory procedures. If harsh shifting is only happening in one range, then replacing the associated accumulator spring might help. K1 accumulator affects shift quality 2-3. K2 affects 3-4.

As for the transmission from the '87, it's a different box altogether. It would be a 722.3, not a 722.4. Since you were planning to have it overhauled anyway, what would be the point? If your present transmission breaks, have it overhauled and go another 300K miles. That's what I did.

Simplifying the vacuum system has many advantages. As these cars age, there are all sorts of vacuum gremlins that can arise...boost issues that can be very difficult to diagnose.

Here's one person's approach:

https://lh5.googleusercontent.com/-9cBEIu4dcas/UAZEQ4LzTiI/AAAAAAAABpI/Xf0tT4reobU/s576/60X%2520Engine%2520Vacuum.jpg

My trans was still going strong on my '95 E300D at 467K. Original trans. Only problem was a 2-3 flare which was manageable by backing off slightly just before the shift, which I had been doing for at least 100K.

Rgds,
Chris W.
former '95 E300D, 467K, gone to new home

My '96 E300D, which also uses the 722.4 transmission, was rebuilt due to a leak at 250,000 miles. The mechanic who did the work said the transmission had another 50,000 miles in it at that time. So your car, Diseasel, is less than halfway there. Make sure the vacuum connections are in good shape and enjoy the car.

A lot of these Mercedes automatics become problematic. In any of mine with automatics I have no reason to think the fluid and filters where changed out at reasonable intervals before I purchased them. At the same time maybe one was but again I doubt it.

Is it the additive packages in the fluid that go bad or get used up requiring the to me frequent recommended changes? The filter should be catching clutch wear particles.

I think the manufacture likes changes every thirty thousand miles. I assume they have a reason. How much additional life the recommended change intervals might allow is also an unknown.

Also the wide range of failure complaints at different reported milages may be due to odometer tampering. Certainly up to 1986 models. I still see all too many of these cars for sale where the indicated claimed milage is a joke. At least compared to the indicators of overall condition of the vehicle. .

15,000, not 30,000 miles
 

MB wants the trans fluid changed every 15,000 miles. I am assuming most people don't change theirs at that level. I change mine every 30,000. I had a problem over a year ago where the car got stuck in 1st gear. One shop wanted $3,000 to fix it. I had my mobile mechanic fix it for $12 plus $50 labor. It was just a plastic piece and there's even a trap door there to get to that part. Someone recommended that he also check the part behind the transmission because some of the plastic fragments from that might have gotten in there and they did.

Once that problem was fixed, the car's been running fine and I have 205k on it now.