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Discussion Starter #1
Hey guys well i went to go buy my first duramax and when i went to test drive it, it would not go when in any of the gears until you gave it some throttle kinda almost like have a stall converter but i know that isnt the case. Turns out it was this Park/Neutral switch that is suppost to be located on the side of the tranny, I am not completely sure I am still wet behind the ears on all this stuff so any insight would be wonderful. Also is this just the start to a wonderful disaster should i stay away from this truck. Mileage is 269000 miles and its a 2004. PLEASE HELP!!!!
 

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Check for codes............... Is it an LB7 or an LLY?
 

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Discussion Starter #3
lly
 

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Mine never did that when the NSBU was bad. It just stuck in random gears, wouldnt go into reverse very well, and made a lot of noise going into gear. Sounds like something besides an NSBU. Did you check the fluid level in the trans or see if it smelled burnt or looked black?
 

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Discussion Starter #5
no i didnt check that, i was so mad at that point i just left anyways so I am going back up there next friday cause the guy said that its all fixed and is gonna replace tranny pan gasket also. so i dont know really nice truck but dont want to buy a new tranny right away. But all fluids will be changed once i get there so i am gonna go drive the truck and see if i can get it to do anything. thanks a million guys i am bound and determined to get meself a duramax. hahaha
 

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Well hopefully he got it fixed up for ya and thats all it was. If it were an NSBU switch the check engine light should have been on, mine was at least when it crapped out. Goodluck and keep us posted on what they found out on it and if you decide to buy it.
 

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The problem you describe is most likely "Converter Drain-back".

If a vehicle sit for a while, the fluid in the converter drains back into the pan- so when you start it, the pump has to fill the converter before it will engage the clutches. After it is full, it should be OK-- until it sits for a while. Some will drain over night, and some will take several days. Doesn't seem to hut anything, just let it idle for a minute and it will drive OK. TransGo has a new valve in their full 5 speed kit, that will help the problem.
 

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I jsut replaced the NSBU in my 04.5 lly. It gave me all kinds of codes and the tranny acted really strange. The first thing that happened was no reverse, the next time it was stuck in 3rd, it made a horrible noise when shifting, almost like the tranny had dropped on the ground ...LOL. It's all good now with a new NSBU.
 

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The problem you describe is most likely "Converter Drain-back".

If a vehicle sit for a while, the fluid in the converter drains back into the pan- so when you start it, the pump has to fill the converter before it will engage the clutches. After it is full, it should be OK-- until it sits for a while. Some will drain over night, and some will take several days. Doesn't seem to hut anything, just let it idle for a minute and it will drive OK. TransGo has a new valve in their full 5 speed kit, that will help the problem.
Iirc. This was a problem in the lb7 5 speed. In the lly 5 speeds you don't install the upgraded drain back valve when building it. They redesigned that valve in 04
 

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My LLY does this after sitting-- but I don't drive it every day! Just let it idle, and it is fine. Takes abt 20-30 seconds to refill.
 
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