Chevy/GMC Duramax 01-04 LB7 Discussion of Chevy and GMC Trucks with LB7 Duramax Turbo Diesel Engines

Transmission issues

Old Jan 16, 2013 | 11:39 PM
  #1  
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Transmission issues
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I have an 01 Duramax Silverado with 240K miles on her. She runs excellent, however, I recently noticed that when I came to a stop, it felt like I had a transmission brake under 10 mph when coming to a stop. My truck did this 3 times on my way home from work about a month ago. It also seemed like my tranny was slipping a little under part throttle acceleration. I put my Stealth 2 programmer on my truck and re-calibrated the transmission and put the 50hp tune in the truck. I normally run the 70hp tune, but I don't beat on my truck. This resolved the problem and was a fix for a month.

So now, a month has gone by and I just started to have the same issue. I was pulling my trailer and when I came to a stop, I did not get the hard slam down into first gear, but what did happen was strange. I came to a stop and it seemed like my transmission was in Neutral after it had downshifted at aprox 5 mph. Then, when I went to accelerate from the stoplight, I was in Drive but the transmission was in Neutral. I brought the RPM's up a bit and it engaged kind of hard. I did not have the RPM's too high, but this concerned me. I got her home and the truck did this 4 or 5 times in a 10 mile trip.

No codes, Oil was flushed every year I have owned the truck.

Any help would be greatly appreciated!

Ozz
 

Last edited by Ozz; Jan 16, 2013 at 11:44 PM.
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Old Jan 18, 2013 | 06:37 PM
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BUMP
 
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Old Jan 24, 2013 | 04:21 PM
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Originally Posted by Ozz
Transmission issues
--------------------------------------------------------------------------------

I have an 01 Duramax Silverado with 240K miles on her. She runs excellent, however, I recently noticed that when I came to a stop, it felt like I had a transmission brake under 10 mph when coming to a stop. My truck did this 3 times on my way home from work about a month ago. It also seemed like my tranny was slipping a little under part throttle acceleration. I put my Stealth 2 programmer on my truck and re-calibrated the transmission and put the 50hp tune in the truck. I normally run the 70hp tune, but I don't beat on my truck. This resolved the problem and was a fix for a month.

So now, a month has gone by and I just started to have the same issue. I was pulling my trailer and when I came to a stop, I did not get the hard slam down into first gear, but what did happen was strange. I came to a stop and it seemed like my transmission was in Neutral after it had downshifted at aprox 5 mph. Then, when I went to accelerate from the stoplight, I was in Drive but the transmission was in Neutral. I brought the RPM's up a bit and it engaged kind of hard. I did not have the RPM's too high, but this concerned me. I got her home and the truck did this 4 or 5 times in a 10 mile trip.

No codes, Oil was flushed every year I have owned the truck.

Any help would be greatly appreciated!

Ozz

Some of the banging / unloading when coming to a stop is often cause by the input shaft of the drive shaft "sticking".

Not sure on the "neutral" issue but you could have a couple things going on.
 
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Old Jan 27, 2013 | 11:26 AM
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Thanks for the reply! I was thinking converter?
 
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Old May 12, 2013 | 09:07 AM
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Did your range shift prohibited come on across your display? recently I am having similiar issues except only when hot, the other day it did not slam like it was under heavy load. i stopped at a light started to excellerate and idle went up but truck did not move put it in nuetral then back to drive and it started going. called diesel perfomance technology in sw florida and he said its prob a sensor of some sort on trans. he will research the issue next week. if i discover more i will let you know
 
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Old May 12, 2013 | 08:54 PM
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likely the transmission is near the end of its life.

mine was doing the same thing, harsh 2-1 shift, neutral when in drive, etc. at the time i was running a 60HP tune. i called up Mike L with Inglewood transmission and he told me that i will need to get it rebuilt real soon. that's then i purchased an upgraded transmission from him. i have now been beating up on it with a 150 HP tune for over 30K mikes and it has been working flawlessly.

i would say, start saving up for a rebuild/upgraded transmission
 
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