But once a week it gives me hard time from shifting 1st to 2nd gear.
Could you be more specific? Does it delay the shift, does it slip in the shift, does it shift back and forth?
Low fluid level can cause shifting problem, but very low fluid level, NOT just a bit low. Almost all of the 3.7L Commanders have the Mercedes NAG1 trans, it is very sensitive to fluid level, do NOT overfill this trans.
The fluid doesn't evaporate, so if you're low on fluid than you likely have a leak. A slow leak from the fittings on the tranny cooler lines is common. As well, if you've lost 2 qts over 175k miles, yea, you can consider that a case you have to add a quart every other year or so, I wouldn't be in a rush to fix it either.
Yes the Mercedes NAG1 trans does NOT have a dipstick, you will have to find the right dip stick off ebay or another source, then you have find a way to measure the fluid temperature (there are several ways) and you check the fluid level against a chart for what temperature the fluid is.
I disagree that a trans is surely worn out at 175k miles. Sure it might be true, but it is also just as likely the trans has lots of life left in it.
I also disagree a shifting problem means a rebuild is needed, it could be a bad sensor. There could be nothing wrong with the trans at all, and the shifting is being caused by a problem with the Drive by Wire system or the Stability Control System.
I also disagree with the attitude of changing the trans fluid and filter will cause a trans to fail. The clutch material is designed to be compatible with the trans fluid.
I see more posts on other vehicle forums saying "I changed the fluid and filter in my trans, and it solved the problem" then I see posts saying, "I changed the fluid and filter in my trans and it failed and needed rebuild shortly after". If your fluid and filter change actually causes your trans to fail, which I doubt, but if it does, then your trans was on the razor of edge of failing any day or mile anyway. Whats the alternative, have it rebuilt without trying to change the fluid/filter? If the worst happens, the only thing you've lost is the time and money to do a the fluid/filter change.
Changing the Fluid & Filter on the NAG1 is no more difficult than any other trans, checking the fluid level is more difficult than other trans, and that is the problem. The reason why they made the NAG1 "Professional Service Only" is because its so sensitive to fluid level, they don't trust the average owner/shade tree mechanic to do it right. Getting the dip stick tool is a bit difficult, measuring the level with the tool is a touch more difficult than your average trans, reading the chart to know the correct level for fluid temp is easy, BUT measuring the fluid temp is difficult, you need an expensive electronic tool or innovate in some way to measure that fluid temp.
One thing I did, I had a clean pan to catch the fluid I drained from the trans, I marked a jug by the quart and then I poured the collected fluid into the marked jug and measured how much I drained. Then I added the exact same amount I drained. Sure enough, when I measured the level it was dead on where it should be. Of course this assumes the trans was at the proper level to begin with
, and if you suspect it might be low, you won't be fixing the problem this way.
Stability Control System
- Every once in a while, I try to pull out on the road with my front wheel turned all the way to one side at a stop, on a wet inclined surface or dirt or gravel, and the engine seems to almost stall, I realize its NOT really stalling, the power just halted a little above idle and it isn't increasing no matter how far I push the pedal. Once I get the vehicle on the road and straighten the front wheels, the power comes roaring back. I think to myself, something must be wrong with my vehicle, then I remember, gee, if I just done the same thing in one of my older vehicles (without Stability Control) I would have been spinning wheels like crazy for those conditions. Then I remember the Stability Control System, how it utilizes the drive by wire to back off engine power the moment it senses a wheel spinning, and realize there was nothing wrong with my Commander, that was the stability control system working like advertised and prevented me from pulling out with a wheel spinning like crazy. Something to consider.