2014 gmc sierra

[Tracy 13]

When driving at any speed truck periodically sounds like your driving over rumble straps.  Any suggestions??

[rav3]

How many miles? 6 speed auto? Any transmission service or work?

My 1st guess is the torque converter is shot. Just saying my opinion. Hard to diagnose your rumble over the internet 

[Tracy 13]

177000 miles, yes  and no transmission work.  T case flushed n filled looked good from what the tech told me.  Had it at 2 different dealerships n truck drives perce t , shifts perfe t.  They are stumped .  

[rav3]

Wonder if they checked for any transmission codes? Check you transmission fluid level, color, smell & for any sparkles in it.

I will assume no check engine light 

[JimCost2014]

+1 for Torque Converter.

[Tracy 13]

Put on diagnostic machine, also drove around for an hour, no codes no nothing.  Levels,  color , smell, and everything all good  is what im being told. 

[rav3]

Sorry but over the internet I still say torque converter. Been there done it on a 4 speed chevy transmission. 

Good luck.

I'd take it to a trusted transmission shop if it were me. But, do what you feel good with...

[newdude]

37 minutes ago, Tracy 13 said:

When driving at any speed truck periodically sounds like your driving over rumble straps.  Any suggestions??

 

 

Any speed?  Or is it primarily highway or speeds from 25-80mph?  

[Texasdeere]

Sure sounds like the Converter.  If you don't know much about transmissions I would get a second opinion on the fluid.  If it was recently serviced then you could try dumping in some Additive.  Might buy you some time.