Odd drivetrain noise when cold coasting down driveway in 1st gear

[C-Mack]

Brand new Grenadier with less than 200 miles on it (literally just drove it home from dealer) and I’m experiencing an odd scraping/rattling or rough bearing type sound while coasting down a gentle driveway first thing in morning the last couple of days. The sound lasts for about 50 to 100 yards then goes away. Checked all the usual suspects, heat shields, loose hoses, transfer box cables interfering with driveshaft issue but find nothing out of the ordinary. It’s a mechanical rotational type noise and sounds like something loose in the transfer case or driveline.

I’ve also noticed a slight knocking in the driveline when slowing down at intersections or stoplights when the transmission shifts down from second to first gear. Needless to say, I’m very concerned to be experiencing these type of issues so soon after getting the vehicle. The dealership is a 90 mile drive away and is a bit of a gauntlet to get to but I can’t seem to track the noise down in order to give the dealer a better idea of what to look for. I’m concerned it won’t be repeatable problem for them. This only seems to be happening when the vehicle is coasting not under any load or throttle application. Not sure how to proceed on this one?

 

[anand]

The sound just sounds like a bit of rust on the rotors from overnight dew/mist, and if that is it, it is completely normal.

As for the "knocking", that is just the trans shifting into 1st gear

 

[C-Mack]

Good suggestion, I did briefly think about brakes as I’m sure they are still bedding in so I’ll keep monitoring and see if the situation improves. Vehicle is kept in a garage with low humidity and I’m in a dry climate so slight rust overnight seems unlikely but maybe some rust buildup around the edge of the rotors from initial transport or sitting at the dealer is catching the edges of the pads until everything beds in?

 

[anand]

Good suggestion, I did briefly think about brakes as I’m sure they are still bedding in so I’ll keep monitoring and see if the situation improves. Vehicle is kept in a garage with low humidity and I’m in a dry climate so slight rust overnight seems unlikely but maybe some rust buildup around the edge of the rotors from initial transport or sitting at the dealer is catching the edges of the pads until everything beds in?

Perhaps... Mine lives outside and has a bit of this every so often in the morning, as does our Sprinter. One brake application skims the surface contaminants off and it's back to normal

 

[Eric]

Good suggestion, I did briefly think about brakes as I’m sure they are still bedding in so I’ll keep monitoring and see if the situation improves. Vehicle is kept in a garage with low humidity and I’m in a dry climate so slight rust overnight seems unlikely but maybe some rust buildup around the edge of the rotors from initial transport or sitting at the dealer is catching the edges of the pads until everything beds in?

Both my vehicles do first thing in the morning when slowing reversing 50m down the drive and gently touching the brakes. This clears the condensation rust by the time I get to the bottom of the drive, then all clear

 

[C-Mack]

It sounds like a mechanical noise and is coming from the center of the vehicle. Usually you can tell if it’s a brake rotor type of scraping noise or even feel through the pedal as the rust is burnished off when you press on the brake but this feels and sounds independent of that. Somewhat paranoid when we took delivery the salesman demonstrated how to lock and unlock the diffs on the dealer asphalt lot and I’m worried it caused damage to the diffs being on a hard surface. Tried to only drive straight and less than 5 mph so not to bind anything up. Praying that didn’t break anything!!

 

[anand]

Somewhat paranoid when we took delivery the salesman demonstrated how to lock and unlock the diffs on the dealer asphalt lot and I’m worried it caused damage to the diffs being on a hard surface. Tried to only drive straight and less than 5 mph so not to bind anything up. Praying that didn’t break anything!!

That definitely didn't damage the diffs, no concern there