Transmission issue after service

2545 Views 13 Replies 5 Participants Last post by jftu105, Dec 7, 2014

4BENZ

Discussion Starter · Nov 25, 2013

Just got my tranny fluid changed (Dextron III) including draining my torque converter along with new filter and gasket. FYI, the tech is a former MB technician for many years who is independent now, and he knows his stuff.

We have had a bit of a cold spell here in the pacific northwest, so I warm the car 5-10 minutes before driving it.

My car, being a 1990, starts in 2nd gear.

The issue is that even after warming it up, when I drive for the first 5 minutes or so, if I accelerate quickly, the car will shift from 2nd to 3rd (the shift is fine - not hard or slipping), but the engine will rev up for a second or so after it went to 3rd gear, then the RPM will drop to the normal range.

So I am accelerating, it shifts up fine, but even after it shifted to 3rd the revs will go up for a second or so later, then drop down. After, the car has warmed up more (10 minutes of driving), I don't get this issue. Just when it is sort of cold.

FYI, I had the transmission rebuilt 4 years ago, and I have about 20,000 miles on it or less (odometer stopped working for a bit, so not sure the exact mileage). Never noticed this before my service (transmission, coolant and rear diff fluid, and power steering fluid changed) last week.

I have not checked the transmission fluid level yet - could it be that?

Any thoughts - or is it something completely unrelated to the transmission?
Thanks.

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1 - 14 of 14 Posts

Jayare

· #2 · Nov 25, 2013

Check your fluid level with the car fully warmed up, running, in park on flat ground. I suspect your fluid level is a tad low.

Good luck

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Clarkz71

· #3 · Nov 25, 2013 (Edited)

Two things, since you've driven the car over 20,000 miles since the rebuild
I'd say you would have noticed the "flare" on the 2-3 shift before, if it were there.

If the fluid were low, it should affect more then just the 2-3 shift, though I would still
make sure the fluid level is correct.

There is a kit to repair this issue, a spring and plastic piston parts kit
for the valve body. An update if you will. The part # 126 270 44 77

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Clarkz71

· #4 · Nov 25, 2013

Here's the kit, your Mercedes tech should know about it and be able to install it.

I'll see if I can find the work instructions on WIS, if I do I'll scan and post.

See less See more

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ps2cho

· #5 · Nov 26, 2013

I did it on my prior transmission and it worked really well. Very easy to do as well...Part should be less than $15 in todays dollars.

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Clarkz71

· #6 · Nov 26, 2013

ps2cho said:
I did it on my prior transmission and it worked really well. Very easy to do as well...Part should be less than $15 in todays dollars.

Yes, that's been around quite a while, I'll see if I can fine the service bulletin
so we know "how long" it's been available.

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4BENZ

Discussion Starter · #7 · Dec 5, 2013

Well, I went back to my Mercedes tech, and he said sometimes the rebuilt shop puts in additives in the trans fluid, which can affect the seals - and this might be the problem.

So I contacted the shop and the owner (who I dealt with 4 years ago), said they use no additives. He also said, Dextron III is no longer available, they use Dextron IV now. (but my tech put in Dextron III)

I don't think it is a valve body issue with my car, because in the 15 years I have had it, I have never had this issue before until the transmission fluid was changed the other week.

Any thoughts on what I should do now?

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Clarkz71

· #8 · Dec 5, 2013 (Edited)

4BENZ said:
He also said, Dextron III is no longer available, they use Dextron IV now. (but my tech put in Dextron III)

BS. Dexron III is still current and availible.

GM does say VI is backward compatible though.

Why haven't you mentioned the kit above
that could fix this issue?

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4BENZ

Discussion Starter · #9 · Dec 5, 2013

Yes, I did mention the kit to my MB tech, he didn't think it would be it.

The day I drop off the car, it didn't have this flare issue, but the day I picked it up, I get the flare. Maybe by coincidence, it failed that day, but I don't think so.

Also, he checked the fluid, it was between the 2 marks - he said the level was fine.

And I agree, with you, Dextron III is still available - that is what my MB tech put in....maybe the transmission shop supplier no longer carries it? And Dextron VI is supposed to be semi-synethic I believe - I don't know if that is a good to put in our older trannys.

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Clarkz71

· #10 · Dec 5, 2013 (Edited)

4BENZ said:
Yes, I did mention the kit to my MB tech, he didn't think it would be it.

The day I drop off the car, it didn't have this flare issue, but the day I picked it up, I get the flare. Maybe by coincidence, it failed that day, but I don't think so.

He doesn't think that's what it is???

It's a known issue with a Service Bulletin.
You want to live with it or try something
that may fix it, but won't cause another problem?

Maybe he doesn't "want" to install it?

Dexron VI is backward compatible. Don't believe
that's an issue.

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4BENZ

Discussion Starter · #11 · Dec 5, 2013

If I put that kit in - should my tech cover the labor? What would the book rate labor be if I was charged for it?

And I am concerned if installing the kit could cause another problem. What could that be?

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Clarkz71

· #12 · Dec 5, 2013

4BENZ said:
If I put that kit in - should my tech cover the labor? What would the book rate labor be if I was charged for it?

And I am concerned if installing the kit could cause another problem. What could that be?

No, the kit is not an automatic part of a rebuild.
Though I personally install them on older transmissions
if I don't know the history of a unit.

I would say 1.5 hours is the maximum labor.
Very easy update for an experienced MB tech.

No, it does not cause a new problem, even when
installed on a transmission without a flare issue.

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4BENZ

Discussion Starter · #13 · Jan 7, 2014

Problem Fixed

Solved the problem.

My tech looked into it, and since the flaring issue only happened when the car is cold, I had to leave it with him for a while.

Problem was the Shift Modulator was leaking (or also called the Vacuum Modulator). He showed it to me and tested it in front of me as well to show it was leaking vacuum. My tech said it looked like the original part and so it was never changed during the rebuilt and the part is only $40 something bucks. And I got the fluid changed just when there was a cold spell (below 32 F) so that is probably why I noticed the problem then.

It should have been changed when the rebuilt was done. I had to spend an extra hour labour because of all this not to mention the time and inconvenience. This is what annoys me

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jftu105

· #14 · Dec 7, 2014 (Edited)

4BENZ said:
Solved the problem.

My tech looked into it, and since the flaring issue only happened when the car is cold, I had to leave it with him for a while.

Problem was the Shift Modulator was leaking (or also called the Vacuum Modulator). He showed it to me and tested it in front of me as well to show it was leaking vacuum. My tech said it looked like the original part and so it was never changed during the rebuilt and the part is only $40 something bucks. And I got the fluid changed just when there was a cold spell (below 32 F) so that is probably why I noticed the problem then.

It should have been changed when the rebuilt was done. I had to spend an extra hour labour because of all this not to mention the time and inconvenience. This is what annoys me

Nice followup to show the true cause of the problem. I guess that Dexron VI is not to be blamed in this case. This is a case of Dexron VI used in a rebuilt, older MB transmission for over four years and 20,000 miles. No early death due to VI as predicted by pundits!?

jftu105

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