Transmission history, maintenance and how should I proceed?

Some of this has been posted in other threads but to recap..

In May of this year I purchased a 1993 Mercedes Benz 300D 2.5 Turbo Diesel with 197k miles. I had it checked at the local dealer where it had been serviced. Both the owner and the dealership indicated that all service had been performed on the factory schedule. In Aug/Sept the transmission started acting funny which I soon learned was slipping and flaring with odd, hard, slow shifting all over the place. It made me really start wondering if the transmission truly had been serviced recently. I called the service manager at the dealership and pressed him to give me a specific of when the car had been serviced. He dug and found that the transmission had not been service since 130k miles!! The next day I took the car in to get the fluid and filter changed (this shop used normal Castrol ATF) which lead to great improvement, in the range of eliminating 90+% of the issues and greatly reducing the ones that remained. The shop indicated that there was “a lot of junk in there.” Needless to say I was very happy with the results!

So how should I maintenance the transmission going forward?

Should I do another fluid and/or filter change soon?
If I change the fluid soon should I get an analysis does and if so why?
What type of fluid should I use? Note that I live in Phoenix, AZ
Is there any fluid I should NOT use basis on its possible condition?

REMAINING ISSUES:

1) Late to shift into 4th when tranny is cold. Once warm it shifts normal.
2) Occasional hard shifts both up and down shifts.
3) Very rare flares. These seem to be increasing as time passes.

Thoughts?

PaulW

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1993 300D 2.5 Turbo Diesel - 201k miles

Just follow the normal schedule. Change it again at 25K-30K. Changing it more frequently won't buy you anything.

Don't know the specification for the 602, however, some folks have claimed that Mobil-1 synthetic transmission fluid is the holy grail.

Don't use any fluid that is not specified for the vehicle other than the synthetic, which has proven to be acceptable.

A late shift when cold is something to ignore. You'll spend all kinds of time and money chasing this issue and it probably won't go away.

"Occasional" hard shifts point to vacuum that is too low. You can diagnose this with a vacuum gauge in the line to the transmission. If you have any vacuum leaks, the trans won't get sufficient vacuum and the shifts will be too firm.

If you have both hard shifts and flaring, this does not bode well. They are mutually exclusive in a properly functioning trans. You can increase vacuum to minimize the hard shifts, but the flaring will get worse. If the two problems are minimal, you'll need to live with it.

So you don't think it would be a good idea to change the fluid sooner then normal to try and flush what ever junk might still be left in there?

PaulW

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1993 300D 2.5 Turbo Diesel - 201k miles

Why do you believe that there is a pile of "junk" in there? When you change the fluid and filter and clean the pan, the junk is disposed of.

The only benefit of a fluid change sooner would depend on whether you drained the torque converter during the last change. If you did, then you're all set. If you did not, then you've got about 2 quarts of old fluid still circulating in the system........something that you've attempted to correct by changing the fluid in the first place.

I could be wrong in my thinking so let me ask a question.

If the fluid condition was so poor and when changed "junk" was noticed how much of this junk do you think still would/could be in the tranny? I see no way that 100% could have been removed.

If there is still some residue in the tranny for the lack of service should I change the fluid again in an effort to "rinse" what ever might remain?

PaulW

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1993 300D 2.5 Turbo Diesel - 201k miles

The synthetic fluid if used will clean residue left behind but if you drained the converter when you changed then the new filter will catch all the residue left behind and will present no problems. Beware of transmission flush services, I wouldn't recommend it. I think you have no worries as Brian has eluded to and just go with a change at 25k.
Bud

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1987 300D Turbo, 175k mi., 1998 BMW 323i Convertible, 1997 F250 4x4 7.3L PSD

Ok thanks that's what I needed to understand!

Thanks,
PaulW

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1993 300D 2.5 Turbo Diesel - 201k miles

The only reason that one might be loathe to use a transmission flush service is the fact that the provider will probably rip you off and charge far too much money for something that they are incapable of doing.

However, if you are unable to drain the torque converter (as I was on the '86), flushing the converter with three gallons of fresh fluid, if properly connected to the flush machine, will provide the oil change that you're looking for.

The cost was $95.00, for which I'm still miffed, but, at least all the fluid in the transmission was exchanged.

Brian, what prevented you from draining the TC?

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Bob
'82 300D Petrol B-G Metallic

Both the shop and I searched for the drain plug for about 10 minutes..........never found it...........

Brian, since I am wary of the types you mention, I usually won't recommend flush procedures. Having said that if one can find a good BG dealer with a good machine and trusted mechanic to use it I would say that would be acceptable. With a MB though, since you can usually drain the converter you shouldn't really need a flush in the first place.
Bud

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1987 300D Turbo, 175k mi., 1998 BMW 323i Convertible, 1997 F250 4x4 7.3L PSD

The procedure is perfectly fine.........it's the shop that performs the procedure that must be scrutinized. But, this is the case with an alignment on a M/B as well. Do you shy away from recommending an alignment for the same reasons?

If you drain the converter, the point is moot.

Anyone have a suggestion on a fluid I should use in my situation?

Paul

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1993 300D 2.5 Turbo Diesel - 201k miles