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Discussion Starter · #1 ·
I have a question concerning my engine RPM’s. I’m new to this forum so if I have this thread in the wrong place, hopefully one of the mods will move it to the right one.
I have a new to me 2001 Silverado, 4x4, crew cab. LB7 Duramax. About half the time when I let off the throttle the tachometer will drop back to 750 RPM’s. Doesn’t matter if I’m running 35, 45 or 65 MPH. Doesn’t usually downshift, however it did one day last week every rime I drove it.i would let off the throttle and the RPM’s would drop to 750 and then after a few seconds would jump up to 2000 RPM’s. You could physically feel and hear the engine down shift and when I pressed the throttle pedal again it would immediately shift back to the higher gear. Transmission is an Allison and fluid level was showing a little low but it shifts fine and smooth with no hesitation in going from park to Reverse even after sitting all night. The trans temp gauge was showing 170 degrees and that is the first time I have noticed it that high. it was 84 degrees outside that day. Hasn’t down shifted like thatsince but the tach does drop to idle speed about half the time. Anyone ever had this issue? Thanks for any and all help in advance. Y’all have a blessed day.
 

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2017, 2500HD, LTZ, front guard, Duraflap mudguards, Leer bed topper
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When conditions are just right, my 2017 does almost exactly that. Throttle off, Coasting with slight uphill grade enough that truck is decelerating.
 

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Definitely make sure your trans fluid level is correct.
 
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Discussion Starter · #5 ·
I did top it off. I also ordered 4 gallons of TranSynd transmission fluid, spin on exterior filter and new drain plu. Gonna drain pan, change spin on filter and drive for 30-40 minutes then drain pan again and refill. Ont know how long previous owner has had the fluid in it. He used Royal Purple fluid and oil. Already changed motor oil and filter. Put Shell Rotunda T-6 in it and Purolator One filter.
 
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