2014 GMC lifted Sierra slipping while going thru gears

[KBB]

Hello All,

Brand new to the site... I have a 2014  GMC Sierra lifted 5.3L (with 84K) that my son is driving ..He said he was on the highway for about an hour and came to a traffic light and the truck turned off... He turned back on and with cruise control on the truck rpm surged to 6k   and ever since has been shifting loudly and seems to be slipping..   He said it sounds like something is spinning and not catching... 

I appreciate any advice or thought...

Thanks,

KBB

P>S> I also have a 2017 GMC Sierra Denali 6.2 L 

[HeySkippyDog]

What does the transmission fluid look like?

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[KBB]

The Trans fluid was level and a brownish color ...

[TXGREEK]

Should be relish in color. Have your transmission serviced by dropping the pan, cleaning out filter and have it refilled with Amsoil Trans Fluid.


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