Driveshaft spinning in neutral?

[solesurvivor]

So I am swapping out my hacked up transmission pan on my W300. Removed, I wanted to see what engages and what doesn't when I pull and push all the levers. Everything works the way it should and drives just fine(as fine as a W300 can).
So the truck is idling in neutral. NP201 is disengaged(front axle). I notice the driveshaft spinning from the T98A to the transfer case. Truck isn't moving and the ebrake stops the driveshaft from rotating and so does depressing the clutch pedal.
So...why is the driveshaft spinning with the trans in neutral?

[W_A_Watson_II]

When you depress the clutch pedal I assume the intermediate drive shaft stop spinning. Also I assume whit the transfer-case in neutral and place the transmission in any gear the truck dosn't move. The neutral drag in the transmission is what you are seeing. causing the intermediate shaft to spin.

[solesurvivor]

When you depress the clutch pedal I assume the intermediate drive shaft stop spinning>YES<. Also I assume whit the transfer-case in neutral and place the transmission in any gear the truck dosn't move>I didn't try that. But I will in the morning.< The neutral drag in the transmission is what you are seeing. causing the intermediate shaft to spin.

>Is that normal? <

[Desoto61]

Like W.A. said, as long as it stops easily then yes. It's just friction (mechanical and fluid) between the spinning input shaft and the open output shaft. Normally the output shaft is locked to the wheels and you can't see that friction. It's basically a visual representation of why fluid in your transmission heats up as you drive.

[solesurvivor]

Thank you both. I feel better now. There are a lot of things going on down there. I changed every fluid down there, steam cleaned everything and nothing leaks. Still only goes 50 miles an hour. I have shimmy around forty. Two guys told me my center link is bent and its causing a toe in issue. You can tell if you stand in front of the truck. It wouldn't matter so much if the truck was in the dirt all the time. But I'm in the middle of the city with nary a patch of dirt at least 50 miles away.

[DrPepper]

You can check your own toe in with a Sharpie felt marker, roll of 2" masking tape and jack stands. Lift axle off ground on stands under frame (more room to measure), wrap the tire with tape on center tread and spin it with the marker steady so you get a close, consistent mark around center of both tires, Then measure the marker line front and back from wheel to wheel. Within a 1/2" wider at the back is okay. Also, gives you a visual on tire tread run out. Works on straight axles only, done this on the family Jeeps many times.

[solesurvivor]

You can check your own toe in with a Sharpie felt marker, roll of 2" masking tape and jack stands. Lift axle off ground on stands under frame (more room to measure), wrap the tire with tape on center tread and spin it with the marker steady so you get a close, consistent mark around center of both tires, Then measure the marker line front and back from wheel to wheel. Within a 1/2" wider at the back is okay. Also, gives you a visual on tire tread run out. Works on straight axles only, done this on the family Jeeps many times.

Cool. I like that. I'll do that tomorrow. Thanks for the tip.

[Matthew Welcher PWA]

I will be honest i have never noticed this before
So with the truck running, transmission in neutral, the transfer case disengaged, not in the neutral position, the intermediate shaft will turn?

[solesurvivor]

Yup. That's why I asked. I never noticed it before either. Except the transfer case IS in the neutral position.

[Desoto61]

I will be honest i have never noticed this before
So with the truck running, transmission in neutral, the transfer case disengaged, not in the neutral position, the intermediate shaft will turn?

It can, depends on a bunch of factors but basically if the friction of the turning parts is enough to overcome the friction of the not turning stuff. A tight bearing in the non-spinning parts, or heavy gear oil in the transfer case could be enough to keep everything still. Alternately a tight bearing in the input shaft or that same heavy lube in the trans could make it more likely to spin. I don't remember the specific numbers but it's a good 12-20% of engine power is lost through the drive-train through friction and such, and it doesn't take that much to spin a few gears or a driveshaft.

I saw the output shaft on my trans doing that when I test fired it in the truck without the intermediate shaft installed, and that's the NV4500 with that fancy synthetic oil it uses. Haven't tried it like this though. I've seen automatics do it when in neutral (my Desoto doesn't have park) and the wheels off the ground. I want to say I might have noticed a tire slowly start spinning on the Power Wagon while in neutral on the lift with the wheels off the ground, but don't remember now, should go look at the video.

[Alxj64]

Its the basic principle of hydrostatic friction drives. Forcing an non-compressible fluid with a specific gravity and specificviscosity through openings will cause a transfer of force through internal friction; any energy that is lost and not turned into work will appear as thermal energy. In this case, the openings are those between the moving teeth and bearings of the input shaft of the transmission. The gears and bearing rollers moving are creating forces through "viscous coupling". Really, its the same principle of how a torque converter works in most all automatic transmissions. Its also why automatic transmissions need lots of thinner fluid so that it can dissipate the heat more efficiently as they have a lot more energy creation through energy loss prior to converter lock-up. A thick oil would perform better for an automatic transmission except for the fact that it doesn't shed heat nearly as well. Similar concept with engine coolant even, otherwise how would a specific gravity meter work for testing your coolant mix ratio? Thinner fluids cool better but also don't lubricate as well because they are too easily moved. Think about it, the fluid between the metal surfaces is what prevents the wear. This is where where mixed grade oils and synthetics come into play. They function at various temperatures maintaining viscosity and lubricity while optimizing their ability to dissipate heat. SO MUCH SCIENCE!