Shifting NP205

[cfarrar]

I have almost no experience driving a 4wd vehicle. A while back, there was a discussion of whether a transmission from a larger truck could be adapted to our Cummins and one of the suggestions for another setup that would create a wide gear range included an NP205 transfer case, the one used in our "W" models, for its low and direct ranges. I know that the NP205 gives a low gear for creeping around, but can one shift it "on-the-fly" so that one can "creep" on the way to highway speed? I'm specifically asking about it being coupled to a Getrag, not an automatic. I'm thinking that maybe by pushing the clutch pedal it could be shifted like a non-synchronized transmission. What is the answer? Thanks for reading this.

 

[BushWakr - RIP]

I think you are okay if your trying to go from 2 high to 4 high on the fly, but not down into 4 low. Expect to grind a few teeth I'm afraid.

In fact there are times when I actually have to stop, shut off the engine, shift out of/into 4 low, and restart.

She can be a bit stubborn.



bob.

 

[tgbol]

I am not sure about the 205 t/c but the 241 in my truck only gives me 2 lower gears. 1st hi is the same as 3rd lo. I have found 4th lo to be of some use when stuck in stop and go traffic. It is higher than 1st and lower than 2nd.

 

[formula]

Couple of thoughts on this... ... .



I assume you're talking about running in 2wd on dry pavement. If you try to shift the transfer case when you're moving and the front hubs are not engaged, you will grind the heck out of the gears in the transfer case. The front hubs must be engaged in order to spin the front driveshaft the same speed as the rear driveshaft. As far as I know there are no synchros in the transfer case.



Using low range 2wd is useful in situations when you have to do slow, tight manuvering with a heavy load. This is especially helpful with manual trannies because you won't have to slip the clutch to keep from going too fast.



Using low range 2wd on dry pavement is hazardous to your drivetrain. The torque multiplication created by the gear reduction of the transfer case, coupled with the fact that the rear drive is taking all of the torque, will dramatically increase the risk of breaking things if you have an itchy right foot.



Sean