Transfer case question

[Octane]

The 77 and 2 79 RamChargers I had were full time as well as the 77 Suburban.

I distinctly remember getting 9 - 10 highway on the 90 mile highway drive to school in the RamChargers, probably a bit less in the Sub.

Yes, you do save wear and tear on the front end, but full time pulled you around corners like a sports car, gave wonderful off the line launches, and a sense of ease in crappy weather or if you just decided to drive offroad on a lark.

If Goldie was full time I probably would not jack with her - cheaper and lazier route.

But, that's my style...

I get 12 mpg with my fulltime 4wd

 

[Octane]

Yeah you’re right. It’ll then send all the power to that front, least resistance, axle.

 

[Turbo4whl]

The fulltime hub has a spline gear and hub so a manual hub lock mounted there has no way to lock or unlock that system

That spline gear is removable. After removing the hub cover one snap ring holds it to the axle shaft. At this point a manual locking hub can be installed. You may find it difficult to remove at this time because rust, or wear on the splines that has frozen it in place.

To install the manual locking hub, you need to take the locking hub apart and assemble it into the wheel hub.

All the early years that the full time NP203 transfer cases were installed this is possible as the front wheel hubs are the same used with the NP205 part time transfer cases.

 

[Goldie Driver]

Yeah you’re right. It’ll then send all the power to that front, least resistance, axle.

Octane is correct - full time 4wd on these has a differential action in the transfer case.
Think of an open rear end- put one wheel on concrete and one in mud - power goes to the mud side.
.Same idea with the NP203, but sub front and rear axle for the wheels in my example above.

The 94 Land Cruiser I had was full time and operated on the same principle.

It, incidentally, got 16 MPG - twice - during the time I had it.

Fuel injected 4.5 liter 6, I think was the displacement.

Built to last (with proper maintenance) but not for gas mileage.

 

[75gmck25]

Based on my experience, the front driveshaft used with the NP203 needs routine maintenance to keep the U-joints and centering ball in the CV joint end working reliably.

The CV joint has two U-joints and a centering ball to keep them lined up, and the joints are changing angles all the time as the driveshaft is spinning. I had the entire driveshaft replaced once, and about 2 months ago had to replace the U-joints and centering ball because a dry U-joint had eaten up the centering ball and it was rapidly clicking as the driveshaft turned. It was a cheap/quick repair to replace 3 U-joints and the centering ball, and I used a non-greasable U-joint this time. YMMV.

Bruce

 

[Octane]

That spline gear is removable. After removing the hub cover one snap ring holds it to the axle shaft. At this point a manual locking hub can be installed. You may find it difficult to remove at this time because rust, or wear on the splines that has frozen it in place.

To install the manual locking hub, you need to take the locking hub apart and assemble it into the wheel hub.

All the early years that the full time NP203 transfer cases were installed this is possible as the front wheel hubs are the same used with the NP205 part time transfer cases.

Im glad mine is fulltime 4wd.Wouldnt want to change it.

 

[idahovette]

Based on my experience, the front driveshaft used with the NP203 needs routine maintenance to keep the U-joints and centering ball in the CV joint end working reliably.

The CV joint has two U-joints and a centering ball to keep them lined up, and the joints are changing angles all the time as the driveshaft is spinning. I had the entire driveshaft replaced once, and about 2 months ago had to replace the U-joints and centering ball because a dry U-joint had eaten up the centering ball and it was rapidly clicking as the driveshaft turned. It was a cheap/quick repair to replace 3 U-joints and the centering ball, and I used a non-greasable U-joint this time. YMMV.

Bruce

My front shaft(75K20 203) has a needle type grease zerk in the center for the ball lubrication, not real easy to get to, but possible.

 

[AuroraGirl]

Based on my experience, the front driveshaft used with the NP203 needs routine maintenance to keep the U-joints and centering ball in the CV joint end working reliably.

The CV joint has two U-joints and a centering ball to keep them lined up, and the joints are changing angles all the time as the driveshaft is spinning. I had the entire driveshaft replaced once, and about 2 months ago had to replace the U-joints and centering ball because a dry U-joint had eaten up the centering ball and it was rapidly clicking as the driveshaft turned. It was a cheap/quick repair to replace 3 U-joints and the centering ball, and I used a non-greasable U-joint this time. YMMV.

Bruce

That sounds like what my dad had, that clicking and grinding with speed. Is there any pics? What were the 3 u joints?

 

[dvdswan]

That sounds like what my dad had, that clicking and grinding with speed. Is there any pics? What were the 3 u joints?

Front drive shaft, similar to this...

You must be registered for see images attach

the right side has the cv joint (constant-velocity) has 2 u-joints in it, then the u-joint on the left side make 3 total.

 

[AuroraGirl]

So the drive shaft to transfer case has a thrust joint to allow minor flex, inward outward motion. The left u joint has the CV, which allows it to rotate at different speeds (preventing binding and issues when rotating different speeds than other side), then the right is a solid axle like most others? That makes sense.
Does lock on the shifter then make both differentials spin all 4 at ssame power distribution?

 

[dvdswan]

Does lock on the shifter then make both differentials spin all 4 at ssame power distribution?

No. Lock means both drivelines have the same power distribution. Differential carrier of the axle determines if the axle shafts have equal, reduced, or no power. i.e. solid locker - equal power to each axle shaft, LSD- limited slip differential - power to the axle shaft that has more resistance, or open differential - one wheel wonder.

Majority of 4WD vehicles are open, open from the factory. Some are open, LSD and very few are lock, lock. Only one I ever heard of being lock, lock were the old Power Wagons but I don't have 1st hand knowledge of it.

 

[Turbo4whl]

Does lock on the shifter then make both differentials spin all 4 at same power distribution?

There is only one differential in the transfer case. It only effects the rear axle. The front axle is always driving. When you shift to lock, that one differential is locked, then both axles are driving.

If you do not have axle limited slip differentials, in lock if one front wheel looses traction and one rear wheel looses traction, the truck is not moving.

 

[AuroraGirl]

Ohhhh okay. So the truck is.. fwd? Until locked? Or do you mean the drive shaft always spins. And the differential is in the center? The rear only transfers energy by gear? If any one has pictures of the whole drive line id appreciate that

 

[Kevin McDermand]

So that's weird that the previous owner said to leave it in N to drive it normally and to shift it to 4 hi and lock in the hubs for 4x4. They obviously didn't know very much about this truck. But I guess the shifter needs adjusted because I leave it in N all the time since that's what I was told. But it makes sense that the couple times I put it in 4 hi to get me out of the mud it didn't work very well because I didn't have it in loc.

You must be registered for see images attach

 

[Goldie Driver]

There is only one differential in the transfer case. It only effects the rear axle. The front axle is always driving. When you shift to lock, that one differential is locked, then both axles are driving.

If you do not have axle limited slip differentials, in lock if one front wheel looses traction and one rear wheel looses traction, the truck is not moving.

Not that this is definitive proof, but I do not believe the above is accurate.

This article mentions things I have always heard and experienced.

For what its worth:

https://www.fourwheeler.com/how-to/47538/