Conductor assembly replaced...post repair problem
 

1999 ML 430

I recently had my conductor assembly replaced to solve a long term transmission issue. All seemed good. In the first 30 days following the repair there was an issue on 4 or 5 separate mornings ONLY during the first cold start of the day (started after sitting overnight). It never happened while driving the car around town or parking and restarting with a 4+ hour break. After sitting overnight and then starting the car I'd let the RPM drop to around 750. Then when shifting into R or D and pressing the throttle the car wouldn't move for a couple seconds, then it would pop into gear. The problem has been very intermittent and hard to reproduce. The last time this occurred after starting, the truck was going in and out of limp mode while I was stop and start driving around town. the problem seemed to be cascading and getting worse, it had not done before in the last 30 days.

Took it back to the Mercedes only indie, no codes. Right before I had the conductor assembly repaired (car was sitting for several months before this repair), I also had part number 210 545 13 32 (part number 74 on the PDF) replaced by an so so mechanic. I'm wondering if he screwed it up or screwed something else up when attempting the repair.

The indie isn't sure what the problem is yet, right now he thinks it's either the shifter/gear selector mechanism or the TCM. If it was a problem with the gear selector switch I had replaced, wouldn't it generate a code? As there are no codes present, the mechanic said it has to be something mechanical or the TCM going bad which wouldn't generate a code.

Thoughts? I'd like to help point him in the right direction if possible.

OK, so the original problem was resolved, but a different issue popped up following the repair?

Assuming the original problem was correctly diagnosed, it sounds like the transmission filter O-ring may not be sealing completely, resulting in the slipping condition you describe. A problem like this would probably be worse when cold. Just a guess but it's easy to check. Let us know how it turns out. :)

Correct. The repair solved the initial problem and the car drives fine other than than the issue I posted about.

I'll let him know to check the O ring. He was a tech at a large Mercedes dealer here for 10 years before going out on his own for the last 10 years. He's the only indie tech I've spoken with that actually seems to know what he's talking about.

Quick tip. If the O-ring is allowing the transmission pump to suck air, you may hear a high-pitched whine/whistle type noise when you increase the RPM. Keep us posted.

Thanks for the tip but there was no whistle or whine when the problem ws occuring so I'm not sure if that's a diagnosis killer. The truck has been sitting in his shop since the 14th :(

Checked the ATF fluid level and it's ok. Checked the filter and O ring and those are ok as well.

He has diagnosed the problem as a defective gear shifter module. $882 to replace new and $640 to replace with a used part. I would think this might be a part one shouldn't get used? Am I right or is the used module a fairly safe bet?

BTW, I noticed the locking pin for cap was missing on the ATF fill tube. Is it possible to buy that part?

Hmmmm..........an intermittent delayed engagement in R or D caused by a bad shifter? Doesn't make sense to me. Is the shift linkage adjusted correctly?

Does your guy have an SDS?

And yes, you can buy the locking pin for the dipstick tube.

Yeah, I'm stopping by tomorrow to chat with him as to how he came to his conclusion. I'm not a mechanic, but I asked him if he was 100% sure and he said yes.

Is the shift linkage the mechanical connection underneath the car and has a couple rubber bushings on it? Procedure described in the attached PDF?

Sorry for asking, but what is an SDS?

SDS= star diagnose system (MB diagnostic laptop scanner).

ie: what type of scanner is he using?

Also do you ever get codes from transfer case?

Yeah, he has SDS as he was able to clear transmission codes before I did the conductor repair/replacement so he could get a proper code reading when the next code was thrown.

He said there were no codes present when the current problem occurred. That's what lead him to either the shifter module or the Transmission Control Unit according to him.

Since he has a SDS, then he is able to READ live data fron the trans module &
see if the trans selector is functioning properly.

Hmmmm....that would make sense then as he was trying to replicate the problem (it's pretty intermittent) to get the data, that's probably why he's had the truck for over two weeks. He's been telling me he has tried to reproduce the issue every day but the truck has been fine. Now he has finally had the issue raise its head again. That would seem to fit with what you're saying.

Be patient with him.

Paid him a visit today and he said he's 100% sure it's the shifter. He GUARANTEES that will solve the problem and if it doesn't, he will refund all the money for the repair. He suggested going with the used part over new.

I'm pretty sure your ML has the early style shifter. It uses a voltage coded gear selector switch (inside the shifter assy.) that can be replaced without much fuss, and for a lot less than $600-800.

Does your shifter have P, R, N, D, 4, 3, 2, 1, or just P, R, N, D with the tip-shift feature?