Transmission Problems?

[JWhitman]

I was very excited to have recently purchased my first diesel, a new 2007. 5 3500 with the 6. 7L Cummins and 6-speed auto. I felt like I was treated well and the price was the best I could find anywhere, but I am pretty nervous about having purchased from Lithia after reading the thread in the third generation forum. At least we have an awesome independent diesel shop here that is certified to do warranty work. Anyway, the truck shifts very hard between 35 and 40 miles per hour. It also slips out of reverse at times when I am backing up. Called the dealer and they said a new flash would fix the first problem, but a new transmission may be required for the second problem. I am slightly concerned about the situation. I am wondering what you experts think about this. I also noticed I have only been getting about 10 mpg highway with this new truck. I currently have 570 miles on it. I am really glad to be a TDR member.

 

[sag2]

The next time it shifts out of reverse, look at the PRNDL and see if it goes blank. This is assuming you are moving more than a couple of miles per hour. If the shifter is not adjusted properly and you are not really in the reverse detent the controller will shift the trans to neutral. This is much more likely your problem than a transmission problem. So far the 68RFE has been very clean.

 

[JWhitman]

The next time it shifts out of reverse, look at the PRNDL and see if it goes blank. This is assuming you are moving more than a couple of miles per hour. If the shifter is not adjusted properly and you are not really in the reverse detent the controller will shift the trans to neutral. This is much more likely your problem than a transmission problem. So far the 68RFE has been very clean.

Thanks sag2. The PRND does go blank when it shifts out of reverse so that must be what is happening. It is encouraging to know that the 68RFE has been a good transmission. What do you think about the gas mileage?

 

[mattymac]

It does seem low but the more miles you put on it the more its going to loosen up. These motors need about 8-10K miles on them before they are fully loosened up.