2 different noises

[McCall Pinz]

I bought my 710M in March and have had a blast with it all over the hills near McCall Idaho. I'm used to older vehicles and aircooled VWs, so I listen and try to understand the various noises coming from Pinz to make sure which are typical and which could indicate trouble. There are the usual tire, wind, rattle, engine noises, but there are two different drivetrain related noises that I'm trying to diagnose.
The first is a high pitched whine similar to a turbo. It occurs at the upper end of the gear ranges and dissappears when I push in the clutch while driving at speed. It is not related to engine speed. I'm pretty sure it is in the gearbox/tranny and it reminds me of an old bug gearbox that needed rebuilding.
The second is a low growling noise that I think is coming from the rear diff. It comes and goes depending on the load applied to the wheels such as accelerating or decelerating and disappears when coasting. Both front and rear diffs are still Exec I models. Does this indicate a rebuild should be a priority this winter?
Thanks for your help

[todds112]

The "growl" is normal from what I'm told. Mine does it exactly as you describe. It also goes away if I have alot of weight in the back. Something to do with the design of the gears and how they mate.

Mine makes a high pitched whine, but it comes from the fan. I notice it more at higher RPM's.

[pinzwheeling]

Every Pinz I've been in gets the gear noise when at speed. I'm assuming it comes on strong about 50MPH?

[Erik712m]

Sound like a bearing going bad or drive shaft needs balanced.

[75pinz]

I have had nine or ten pinzgauers. They all made a lot of bad noises. I would suggest ear plugs. The best pinzgauer I have ever seen as far as noise and vibration was Todd112s and it was still loud but less vibration than others I have seen. I wouldn't change a thing unless the noises change in intensity or duration. Of course this free advice is worth squat...The loudest most awful vibrating pinzgauer I have had was also the nicest, newest, best looking truck I have ever seen. I would have swore it was brand new and it basically was but the drivetrain was horrendously loud. It was by far the worst one as far as noise and vibration I have ever been around. I sold it and that guy drives it every day with no work ever on the drivetrain and that was a few years ago. My current AMB has no vibration and is very quiet with the box on the back v. a cargo truck. I think it is just the box that quiets it down. I also think that the 712 tends to have less vibrations in my experience than a 710. I would guess because it goes slower...

[Roman]

Source of the whine are most likely the cone gears within the rear diff.
Mechanical engineers know very well that cone gears are notorious loud (and expensive as well), and are therefore usually avoided as much as possibile. Energy transfer efficiency is also the worst of all types of gear drives.
But it gives the pinz its unique ability to have oscilating axles without need to rely on the universal joints. This way the entire driveline can be encapsulated into one compact unit, resistant to water, mud and dust. I guess that it was the primary idea of the design.
Comfort of the silent ride obviously wasn't high on the priority list for the design of this very special all terrain military transport truck.

Roman

[mjnims]

Comfort of the silent ride obviously wasn't high on the priority list for the design of this very special all terrain military transport truck.

Or on any other military vehicle ever made. Most modern US trucks have "hearing protection required" signs on drivers door.

[pinzwheeling]

I also think that the 712 tends to have less vibrations in my experience than a 710. I would guess because it goes slower...

I had the same thought. Wow, the 712 is much quieter... Oh yeah, I'm going slower. Duh...

[McCall Pinz]

It sounds like both the gear growl and the quasi-turbo whine are actually pretty normal. That's good, then I can concentrate on the carbs, exhaust, and brakes this fall. Thanks again