I have a 2005 Dually 3500 5.9l I-6 w/ auto transmission and recently, it won't shift gears without trouble. This is what happens: I start accelerating, but it requires that I reach 3000 rpms in order to hit 30 mph. This never happened before. Before, it would shift gears normally--never reaching 3000 rpms unless I was trying hard to accelarate really quickly. But ever since I had to change my batteries, I can't get it to accelerate normally.
The temporary solution I have found is to accelerate to 30 mph by letting it over-rev (rpms in the redline area). Then let go just a little but maintain the 30 mph at about 2500 rpms. After a few seconds of this, it may or may not shift gears. Sometimes it catches, sometimes is doesn't. Sometimes it works at lower mph, like 25. Some other times it shifts twice, once at 30 and another at 35. None of my friends (who know a little about cars) know what the problem is...not even the mechanic.
Any idea? Suggestions?
The temporary solution I have found is to accelerate to 30 mph by letting it over-rev (rpms in the redline area). Then let go just a little but maintain the 30 mph at about 2500 rpms. After a few seconds of this, it may or may not shift gears. Sometimes it catches, sometimes is doesn't. Sometimes it works at lower mph, like 25. Some other times it shifts twice, once at 30 and another at 35. None of my friends (who know a little about cars) know what the problem is...not even the mechanic.
Any idea? Suggestions?