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Discussion Starter #1
I have had my 08 SLT for a few days now. This is my first diesel and so far I am very happy with it. So there's this old man I know with a 07 dura, and he was telling me that the 6th gear was only usable in manual mode. I assured him that was not true. I decided to do a test to see why he would have thought this. I was going 50mph and put it into manual and it showed M5. So I put it into 6th and within about 7 miles my average mpg went up 1.2 mpg. So I'm thinking this is cool, but I don't want to have to manual shift all the time. turns out if you use manual mode and just bump it to 6th, you can drive normally. Runs just like it's in drive, but will go into the 6th gear at lower speeds. Even went over a bridge and the rpm's never moved. Just thought I would share this. Maybe most know this already. Hope it helps others improve city/slower driving mpg.
 

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GM FREAK
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Sorry, but I call bullshit. There is no truth to that. I have a buddy with the 08 and he confirmed that it's BS as well. That old man you referred to is jerking your chain.:nono:
 

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Well at 50mph you're going too slow to go into 6th gear. If you're running 32" tires with the stock 3.73 gears you would only be turning 1195 rpm which is lugging the shit out of the engine and really isn't good for it.
 

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Discussion Starter #4
I never believed the old timer. I told him it was a 6 speed tranny no matter what. I was just thinking that using manual mode is why he might of thought that. Also I found that when in manual mode it shifts just like in D until it gets to the highest gear selected. So you really can't manually put it into 6th if you are going to slow. Not sure why the average mpg went up when I put in it manual and selected 6th, but it did. At 50 selecting 5th or 6th had no rpm change. Sorry for jumping the gun on this. Got a little to excited I guess. New truck brain fart. Lesson learned.
 

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Discussion Starter #5
Well at 50mph you're going too slow to go into 6th gear. If you're running 32" tires with the stock 3.73 gears you would only be turning 1195 rpm which is lugging the shit out of the engine and really isn't good for it.
Running 285 17's. I think it was at 1400 rpm @ 50 mph. It was a stupid post. I know that now.
 
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