hey everyone,

been looking for a GC for awhile now. mainly want a good vehicle for all the weather we get here in jersey with minimal if any offroading. for full time 4x4 what differences are there between the two cases in the way power is transfered? in the 249 is all power going to the rear until the VC detects slip and then transferes or is there always some kind of split between the two axles that just varies based on slip?

been trying to find out more about the 249 but searching hasnt brought up alot on how it actually distributes power.

Thanks
Mike

 

I beleive the NP249 uses a viscous coupling for its 4wd HI, it works like you said all the power to the rear until there is slip then it starts trickling power to the front. They also have a hard front-rear lock on them while in 4-Lo, and no 2wd option.

The 242 uses an open center diff, more power is sent to the axle with the LEAST traction, for a rough example if the front axle has 80% of the traction it only gets 20% of the power or if the rear has 10% of the traction it gets 90% of the power. Sounds bad but it still works allright for anything onroad, like snow or dirt. You can lock the center on them however for true 4wd HI and they have a locked low range and a 2wd option as well.

Basically I think the 249 is a hair stronger and works a little better but its also quite a bit more complex.

 

ok so i understand it in the 249 all the power is to the rear until there is slip and in the 242 there is always some power split between the axles?

 

I recently looked in my 93 factory service manual regarding both np249 and np242. Seems like the np249 has a open differential in addition to the viscus coupling, the np242 uses only a open differential, and multiple range operator selections...ie 2wd, 4hi, 4full, 4low, N. instead of just 4full, N, 4Lo of the viscous coupling 249

 

Yeah the 242 sends power to both axles equally if they both have equal resistance (traction), if one starts to slip it actually will send more power to that axle or it one catches traction it will send less power, but you can also lock the two axle togther so they have to turn at the same speed in 4 Part time, though it will break things if you engage that function on dry pavement. Like I said, it's the opposite of what really should happen but thats how all wheel drive in most cars works.

To be honest I wouldnt worry about which one I get, for what it sounds like you want, both of them will be more than adequate.