Welcome to DF!

I would put money on NSBU Switch.
On the side of the transmission under your linkage.
LBZ's have one plug.
Have you gotten "Range Shift Inhibited" on the DIC yet?

 

The only codes it ever threw were the ones it originally threw (P0729 Gear 6 incorrect ratio P0567 cruise control signal and P0700 Trans control syst malfunction) and like I said it quit throwing any codes.

 

PO700 is a generic code..
Theres more to it, you'll need a better scanner to figure out exactly.
But my money is on the NSBU Switch, use the search tool and check out the threads.
There is a lot of information on that switch and its a common issue.
Its $120ish, and a two beer minimum job.
Good Luck!

 

I searched here and other places for those codes but found no similar issues to mine. I have not searched that switch but will do so now and come back here after I find something. Thanks for the info because I feel like I have been smashing my head against a brick wall.

 

Let me know what you figure out.

 

Something I also just thought of two or three times I tried starting the truck and it did literally nothing.

 

You see your gear indicator on your DIC?
When you tried to put it into reverse for example, did the little line underneath "R" disappear?

 

If I remember correctly turning key there was nothing in the screen. Then when I relaxed the key I could see the gear selection, pulled it into neutral then back to park and believe I could see it.

 

Hmmmm
Others may have to chime in, but I sticking to the NSBU Switch being the problem..
There are ways to test it, but I am not sure. I replaced mine with the same symptoms as you.. But I do not want to steer you in the wrong direction as well though..

 

I will search and come back here if I find anything. Again I appreciate your help

 

You're welcome bud. :high5

 

This may sound like a stupid question but I called the dealership and they said they do not find that part for my truck. Is it called something else?

 

It is NOT the NSBU switch as the 6 speed does not have one. They use a Mode Switch that is inside the trans, and does not give much trouble like the NSBU switch

Possible the transfer case is worn and it looses the speed sensor when going over bumps. You need to monitor the speed signals with a Tech II- when it happens.

Moved to Trans for more help.

 

When you say looses the speed sensor when going over bumps, what do you mean by that? I am really curious as I think I have symptoms like this in my "brand new transfercase"

 

Ahhhhh crap
Sorry man, I am in my own little LB7 world and totally forgot that....
My bad....

 

The transmission speed sensor is in the back of the transfer case, if it looses the speed signal, it can affect trans shifting. Check the big plug in the back of the trans-- make sure it is in all the way and secure. Follow the harness and look for shorts a wear. Of course make sure the trans fluid is in the middle of the hash marks while warm and running.

Drain the transfer case and look for metal- check the output shaft for up and down-- and in and out movement.

 

Fresh fluid, just did a double drain and fill
Now if any of those sensors were bad or the transmission is slipping, won't it throw some kind of code?
Output shaft is tight, no movement what so ever.
Fluid was just replaced for the first time since reassembly, looked normal, will do another change again to insure.

 

Like jc said prolly the transfer shitting the bed. My friends did the same thing and a week later it grenaded going 80 down I 70. Tore shit up.

 

Welcome..... Olympia truck here as well. We do have a hidden gem up here in Washington.I know it is a shitty feeling having something wrong with a new truck.. I am sorry but...

Sdp up in port Angeles is one of the best duramax/Allison guys in the country. Maybe trailer or run the truck up to him

 

I run synthetic tranny fluid in mine.. Torque Drive
Its only a few qts

The fluid will have a little metal hue to it but you should see no flakes.

 

I bet the tail shaft bearing and copper or brass (can't remember) ring is gone. When you hit a bump it's moving and not lining up for the speed sensor and throwing the code. Don't drive it or you'll risk damaging the driveshaft and possibly busting your fuel tank and lines.

 

It does it when I am just driving sometimes, and last week got drastically worse to also doing it usually when I let off the fuel pedal. Could it still be the tail shaft bearing? If so how do I check it and (not to sound like an idiot) where is it?

 

http://www.duramaxforum.com/forum/how-tos-diy-write-ups/89225-how-gm-transfer-case-pump-rub-kit.html


This will give you an idea. The rings holds the shafts in place. Put your truck in neutral and chalk the wheels and move the driveshaft up and down. There should be minimal play, yours prolly moves a lot

 

http://www.duramaxforum.com/forum/0...-07-lbz-lly-duramax-powertrain/190297-transfer-case-output-shaft-play-slop.html

 

This is a pic of it, does this look normal? I pushed up and down and seemed no movement at all but did seem to have a bit of slop turning the driveline.

 

Have you drained the oil yet?
Three things make it leak, bad ring/bearing, worn yoke, or a bad seal.

 

No I live in the sticks and have to go to Oly to get the replacement fluid. I volunteer at the school coaching the wrestling team so plan on going to get it after practice tonight and will drain it tonight if it is not raining too much.

 

Make sure you at least check it. If you can't feel it with the first joint of your finger it's low. I have smaller fingers and if I can't touch it with my second pinky knuckle I won't drive it till I add oil.