I was driving back from minnesota last night, doin about 70-75 after about an right about the iowa border I start noticing a slight surging around 74 MPH. it was REALLY slight, but enough that my wife noticed it too.

I was mixing between 4 HI (going about 60mph) and 2, as the roads had some iffy spots left over from the storm. I had filled up before we left, and added some PS.

If I was going by the instrument panel, I wouldn't have believed the surge was happening, the RPM's were constant, everything was holding steady.

is there something I should be checking? I don't know where to start.

 

Maybe a little tire slipping? Was it happening while you were in 4x4?

 

seemed to only be noticeable in 4. but it was so rhythmic, it didn't seem like slippage. I will try and re-create it today.

 

possibly drive train binding and unbinding in 4wd ?

 

Was this in cruise control? Mine and several others trucks will surge going down hill in cruise control. It is annoying but normal.

 

wasnt in cruise, I avoid that when the snow flies. could have been binding, it was changing from ice and snow to pavement quite frequently.

 

That was my idea when I asked if it only happens in 4x4. If it doesn't do it in 2 wheel, it's probably binding. You don't have different tires on front and rear or anything like that do you? Different loads, pressures, weight?

 

you guys might be right, all 4 tires are the same, tire pressure was the same. not much weight in the bed, just a couple hundred pounds.