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Discussion Starter · #1 ·
so i roll from about 60-70k, brake, come to a complete stop at a red light. sit there for a few minutes, go to go over the overpass and onto the offramp. Truck wont move when i let off the brakes. give it gas, finally starts to move probably around 1200-2000rpm? i assume it is ice on the overpass and continue to drive.. no jerking or anything. next time i stop, same thing happens. so i know something is up. pull over, check my transmission fluid, within warm max (had been using the truck a few hours prior to the first stop on this trip) so i drop my friend off, and check the codes after making a terrible three point turn (actually heard clunking from letting out of D, slipping into R, and back into D.. Noise all three times. shut off engine to check codes with key turned on, wrote them down, turned it on, and it drove fine all the way home... Kind of odd?

P0700
P1723
P1643
B0077 - known airbag issue.

Assuming my tranny is pooched? at least first, if not worse? :help
The truck is a 2001 LB7 extended cab long box silverado. Just did the top end of the engine, injectors/glowplugs/headgasket, as well as a new water pump and idler pulley that ceased.. Was gonna cost 12k at dealer, did it for around 5 myself... not really looking forward to another 5-6 for a tranny without install.

Thanks guys, sorry if i broke any rules for the fourm, i've never made a post, and its kind of urgent cause its my daily driver.
 

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Welcome to the duramax forum. I am not sure what the codes are but someone who knows more about trannys will help you out soon. What I do know is when the computer on the side of your transmission starts to screw up it does a similar thing. On your dash does it show that your in the right gear? Or does that skip around or not light up at all?

And please fill out your signature it will help us out
 

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It won't be 5 or 6 for a tranny. I'd say 3500 would get you a built one, you can probably put a stocker in for less
 

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How many miles (km) on your truck? Very weird. Good luck.
 

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Sounds like an NSBU switch. Exactly what mine was doing. Its the switch on the drivers side of the transmission that the shifer cable runs to. $80 for a good switch. A few vendors on here have them. Cheaper route at least to try than a new transmission.
 

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Discussion Starter · #6 ·
my truck is just shy of 400k km, but i replaced the NSBU unit on the side, and cleared my codes... it only did the stalling in first thing once like i said, but i swapped that out for 60 bucks from my local gm dealership, and looks like it might be alright.. i also failed to mention that when i get up to 120-130, once in a while it will redline and not shift until i let up on the gas.. i bought it with 281,000 on it, and it had the hypertech III running on it.. redid the injectors, glowplugs, headgasket last year and haven't used it since (the tuner). Also just did the water pump.

Still sort of concerned with the tranny, but if it isn't hesitating anymore off the line i'll start putting money aside incase it fails, any specific builds for the lb7 anyone would recommend for trannys?

Oh, and since i switched out that nsbu module on the side of the trans, every few times i shift the gear indicator goes out when i go from P to D. Could it just need to wear in a little?

Thanks again guys, at least its back on the road, and no codes of yet!
 

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have you checked the tranny fluid level yet?
that would be the first thing i would do.
had it happen to me, but i was pulling the wedge trailer, and it would not move in the morning, so i checked tranny, and was a quart low.
so check fluid levels first. you could have a small leak.
 

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Discussion Starter · #8 ·
yeah i did, i was right in the middle for the full mark when the engine was warm, i haven't checked it from cold though. I checked it a few weeks back and it was low, so i topped it off (also warm) so i'd hate to say this, but maybe it's overfull (cold?) and the fluid is expanding at the wrong rate? Or, since its the original tranny with like 400,000km... it could be on its way out. or it might be because it used to be on the hypertech tuner!
 

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P0700 is limp mode, what you felt when that happened was the truck was in 4th gear locked and won't shift up or down for safety of the trans due to a 5% or more slip of the clutches in the trans and or something else causing it to freak. It being stuck in fourth would take til about 1200-2000rpms to move the truck like you said, and if it were to keep doing that it may fry your torque converter due to so much slippage while trying to move the truck. Believe me I've done it. As to why it did this? I have no explanation for that. Nor do I have a fix. Hope my input helps some.
 

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my truck is just shy of 400k km, but i replaced the NSBU unit on the side, and cleared my codes... it only did the stalling in first thing once like i said, but i swapped that out for 60 bucks from my local gm dealership, and looks like it might be alright.. i also failed to mention that when i get up to 120-130, once in a while it will redline and not shift until i let up on the gas.. i bought it with 281,000 on it, and it had the hypertech III running on it.. redid the injectors, glowplugs, headgasket last year and haven't used it since (the tuner). Also just did the water pump.

Still sort of concerned with the tranny, but if it isn't hesitating anymore off the line i'll start putting money aside incase it fails, any specific builds for the lb7 anyone would recommend for trannys?

Oh, and since i switched out that nsbu module on the side of the trans, every few times i shift the gear indicator goes out when i go from P to D. Could it just need to wear in a little?

Thanks again guys, at least its back on the road, and no codes of yet!
The not shifting until you let up on the gas is normally caused by a plugged fuel filter. All I can say is you are living on borrowed time if you are actually limping your tranny (which sounds like you are by the P0700 code) it is only a matter of time until you have to rebuild or replace the tranny. I know I have limped mine a couple of times and it gets easier and easier each time...it slips more after the limp too. I will be doing a tranny kit fairly soon on my truck.
 

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P0700 is a code you get when the tcm send a signal to the ecm to illuminate the MIL you would really need to pull the codes from the tcm to see the real issue.

P0700-Transmission Control Module (TCM) Requested MIL Illumination
P1723-Solenoid A Controlled Clutch Stuck On
P1643-Wait to Start Lamp Control Circuit
 

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Discussion Starter · #13 ·
well when i replaced the nsbu unit and cleared the codes, it hasn't been limp off the line anymore, but today when it was under heavier acceleration it didnt wanna make the shift at 120-130 (im assuming 4 to 5 gear, i've never done tranny work before). Hasn't coded at all yet, so i'm kind of just taking her easy and going through driving cycles to see if any codes get thrown.
 

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Discussion Starter · #14 ·
i change my fuel filter almost every oil change (every 5000km or so) which is overkill, but i'd rather be safe than sorry.. but maybe i will change it again to be safe, haha.

Yeah, i'm assuming its the transmission, but i've never done any work on one so i'm kind of weary on trying to do a tear down and rebuild on my own, i know i'd save a ton of cash but i don't really have the time or experience for a rebuild.

i did the headgasket, injectors and glowplugs and that was a first time as well, but it ended up taking about 40 hours or so with all the part scrubbing and ordering piece by piece that needed revamping as i noticed it on the tear down.. and the tranny is a little more finicky than top end work haha.

i'm assuming since i cleared the codes with the reader i also cleared the tcm and it's codes, so there would be no chance of getting those?
 
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