Transmission Problem in ML - PeachParts Mercedes-Benz Forum

sunedog · #1 12-25-2009, 04:55 PM

(I posted this in the ML forum and have had no response for several days.)

My 99 ML 320 has 245,000 miles on it. It had 185,000 miles on it when I had the transmission re-built two years ago.

The truck is sometimes refusing to shift into high gear. The weather is in the 20's here, but it does it when the truck is fully warmed up. It was running fine with the selector in the 4 overdrive position. Yesterday I entered an interstate and it wouldn't upshift. I was only doing about 40 MPH and the tach was reading about 4000 RPM's. I lifted my foot, bumped it into neutral, and then back to 4 overdrive. Pressed the gas and the engine freewheeled like it was still in neutral. I coasted to a complete stop, put in in park, then backed up a bit, stopped, then started forward. The truck ran normally from that point on.

Started it this morning and let it idle for 10 minutes to warm up. In the first minute of driving, it refused to upshift again. I did the stop/park/resume routine and it ran fine all the way to the transmission shop I used two years ago.

(Note: I am aware the computer limits the upshifts in cold weather to let the engine warm up faster. I don't have the exact MPH/RPM numbers in my head, but it was a lot more RPM's per MPH than normal.)

The transmission guy scanned it and came up with 10 codes. I remember codes related to upshift solenoid, a transfer case, oil temp and then a problem communicating with the computer. He stopped and told me I needed to take it to a dealer because he suspects the computer is bad.

Q: Is there a separate transmission computer, or does the main computer control the transmission?

Q: I am currently 550 miles from home. If the truck behaves (upshifts correctly), do you think I can drive it home so I can deal with it there? I don't want to do additional damage to it.

Q: Any other words of wisdom?

sunedog · #2 12-27-2009, 06:32 PM

Drove the truck for the first time in a week. Ambient temp was about 47 degrees today. The truck ran flawlessly. The temps were in the 20's when I had the problem. Do you think the ambient temperature is affecting the transmission?

Thanks in advance.

mbdoc · #3 12-28-2009, 08:34 AM

What were the codes??

Try engaging the transfer case motor from high to low 10-12 times.

You need to have the truck running, in "N" with parking brake on. Then operate switch back & forth.

sunedog · #4 12-28-2009, 10:25 AM

I don't have the codes. The guys scanner would not store them and I didn't think to jot them down until it was too late. I will take the truck to a dealer to read them and print them.

In the meantime, I'll try your suggestion to cylce between high and low range.

Thanks Doc.

oldsinner111 · #5 12-28-2009, 12:17 PM

I was going to purchase a ML 320cdi,but after reading on ML problems no thanks. Its not just ML's but Cs,Es,Ss, you name it. I would not trust one on a long trip. I'll stick to my w126 diesel.

sunedog · #6 02-26-2010, 08:09 AM

Follow up to my original post:

Drove the truck home (550 miles) in cold temps (20's) with zero problems. Drove the truck around for a few weeks here in sunny SC and warmer temps and zero problems.

Took it to my trusted indy mechanic here at home and he thinks I had a sticking valve related to moisture and the cold temps. It's been right at 60,000 miles since the transmission was rebuilt. He flushed it and used 14 quarts of fluid @ $17.50 each to do the flush. Charged 2 hours of labor. Cost was about $475 including tax.