Transmission

[Slow Six]

My truck is a 2012 3500 dually, Max Tow, 68RFE, 4:10 gears. When towing my fiver the transmission shifts erratically. The 5-6 and 6-5 shifts are okay but 3-4, 4-3 and 4-5 and 5-4 shifts are not good. When down shifting it seems like it starts to shift but hesitates and when it does shift it is a hard shift. When up shifting it seems like the engine revs and than again a hard shift. I can help the shifting by using the accelerator pedal. Also when going down hill it will shift down to help check speed which is okay but it usually shifts a gear lower than it should which brings RPMs into the 3000 RPM range. At the bottom of the hill when it stops "jaking" it will shift down one more gear and than shifts up. I have the exhaust brake on and use Tow/Haul. I am towing heavy with GVW close to 30,000 lbs. I don't think this is quite right but I would like to hear from you if this is normal. I have asked dealers about this but all I get is the usual blank stare.

 

[Cummins12V98]

Use the gear you would come up the grade in and set cruise control.

 

[Jim W]

I think this is do to the Tow/Haul and exhaust brake being on together. I have found on my 08 truck when both the tow/haulmode and exhaust brake are engaged the downshifting is very noticeable and harsh. This is do to the shift points being altered from the non tow-haul mode in the transmission controls do to activation of the tow haul mode. It is aggressive but I have become use to this and realize that this is a tow vehicle pulling a heavy camper and I would rather have control of the vehicle than a runaway vehicle.

Just my humble opinion.

Jim W.