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As noted, the truck is a 1999 Dodge Ram 2500 Cummins Automatic transmission, with a little over 408,000 miles.
Recently, the transmission started "hunting" between 45 and 55 miles per hour. Actually, it was the converter locking and unlocking, which gives the same feel as "I can't make up my mind, overdrive or not!"
Went to the internet, that source of wisdom for nearly everything, and found lots of "fixes":
The TCM needs reprogrammed.
The transmission needs flushed and the filter changed.
Replace the batteries.
The transmission needs rebuilt.
The torque converter needs replaced, and while the transmission is out, might as well rebuild it.
Do THIS, it only costs $160!
No, do THAT, it costs $220!
Then I happened to run across a "How To Fix It" video. The guy says just run a ground wire from the negative terminal of the passenger side battery to a ground screw on the firewall (as pictured), clean the battery terminals, and the problem will likely be solved. That screw is the ground for the TCM!
He is right!
The cost of the "fix"? Two feet of 14 gauge primary wire (found in the junk drawer), 2 ring tongue terminals (also found in the junk drawer), and less than one hour work.
No more "hunting", the engine starts better and sounds better and runs smoother!
I do love it when the simple, cheap, fix is the right fix!
Oh, yeah, on a side note, keep in mind that vehicle manufacturers do not believe it is necessary to remove the paint at grounding points. They are more likely to use "shake proof" terminals, hoping that the points on the terminal will dig through the paint and make contact. I believe it pays to remove the paint and get a GOOD ground at the start! But then, I was an A&P mechanic, and we have special tools known as "Bonding Brushes" to do exactly that!
11 days later, and the "cheap fix" appears to be a failure!
the transmission is back to doing the same thing again. At 40 MPH or less, or 55 MPH or more it is fine, but at 45 to 50 MPH (more or less) the torque converter will not stay locked.
At the present time, I will simply avoid that speed range. I can't afford to have it checked out right now, and chances are I can't afford to fix it, either.
Just thought I should let anybody who reads this know that while the ground wire helped, it did not cure the problem.
My buds Ram was doing the same thing. Like it was locking then unlocking the converter. Engine speed would pick up and then fall back via the tachometer. He had taken it to several shops and the dealer and nobody could tell him why. He went thru the flushes, adjustments, a PCM recalibration, all kinds of crap. As we were chatting about it with another friend of mine that's also a self employed mobile mechanic, he said the fix is simple and if he couldn't fix it, it cost nothing. He changed out the throttle position sensor and it fixed the issue. If you're handy with tools, you can do this yourself. Parts are about 75 bucks. If your transmission is acting like that, with the engine rpm running up and down at a specific speed, transmission failure is in your future if you don't fix it. It causes excessive heat in the clutches.
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