About once a month when I first start my truck in the morning, I can shift from Park to R and nothing happens. I tap the accellerator and the engine revs by no motion.

I cap put it in Park and try again and she always goes. Is this the NSBU switch going bad? I have not noticed if it gives me an error message on the DIC.

Thanks

MSK

2004.5 completely stock.

How long do you idle before selecting R? This sounds like simple converter drainback. Of course check fluid level and make sure the spin on is fresh, and park level, but basically try to let it idle for a bit before selecting any gear.

I think the NSBU will fail to light the shift indicator on the column. That's what mine did when it was going out.

jb

I probably did not let it idle very long at all. Normally in a hurry first thing in the morning.

I will try that and see. All lights appear to working correctly when I have experienced problem.

MSK

With converter drainback it could take up to 20 seconds to fill your converter and get moving. This is a normal condition if the truck has not been run for a couple of days.

The shaft sealrings allow fluid to drain out of the converter when not in use. It can take up to 20 seconds after startup to refill.

I had the same problem on an 05 4.8L Silverado with the 4L60. I took it in under warranty and they rebuilt the transmission. They said a seal was defective and cause fluid to leak and was making a carrier or something come apart. A few months later it did the same thing. After that I just traded the truck and got my new duramax. I could leave it in reverse and it would do nothing but put it in park and go back to reverse and it would work. If you have warranty try taking it in. Was not an allison but same problem and it was not all the time, just like your describing.

Recently my buffy with his 2006 Duramax went to shift out of Park to drive, when all of a sudden his column shifter just dropped clear to 1.

Turns out that the shift cable is two piece and a little C-clip looking thing (probably costs 5 cents to make and will cost $100 at the dealer) broke.

Anyway, it could be that the cable is stretched alittle bit and need adjusted. After seeing how it works in person, I would guess that. It might not be engaging all the way. Just shifting it back might be causing it to move enough when it is cold. Try pulling it down into neutral and see if you feel it shift through reverse.

Just my $.02.

I let the truck warm up and after a few minutes, I turn off the truck, let it set a minute, then restart the truck.

Mine was doing that, but I got an error message "Shift Range Inhibited". Turned out to be a couple things. They ended up replacing the NSBU, Ignition Switch, and a solenoid. Works great now.

Ok guys. I let me truck sit a couple of days over the weekend. Definately a drainback problem. I can now reproduce the issue.

My question is should I hound the dealer to get this fixed. I have 87000 miles on my 2004. And don't want serious problems after I am out of warranty.


Any thoughts would be great.

Mark

I don't know if it can be fixed...

I would like to know more about this drain back. I have just lately started to notice if I let my truck set for 2 days it will not move when I first start it. This is on a NBS 07 with only 18k miles. I've had this problem before on a different truck and it wasn't long before the transmission had to be replaced. It had around 100k on it.

I would like to know more about this drain back. I have just lately started to notice if I let my truck set for 2 days it will not move when I first start it. This is on a NBS 07 with only 18k miles. I've had this problem before on a different truck and it wasn't long before the transmission had to be replaced. It had around 100k on it.

While drainback is annoying, its NOT related to trans durability.

Oil drains out of the torque converter past the sealrings on the ground sleeve (stator shaft) and turbine (input) shaft. The torque converter doesn't transmit torque with air in it. Once it fills, about 20 sec max, you're fully operational.

At stock power levels, the Allison can last hundreds of thousands of miles. Most commercial use customers expect a minimum of 300k behind their Caterpillar, Navistar and Cummins engines and at truck ratings of up to 26,000 lbs in daily use.