All,


currently on a 99 i have 4.56,C8.25 with ARB, HP D30 open, NP242

My front diff, no front drive shaft currently, is making noise from the spider gears. I put the stub shafts in to rule out that this was were the noise is coming from, we pulled the diff to inspect the spider gears and I guess they are worn/ a bit loose. I dont know how these are making noise when slowing to a stop, but with the shafts out the sound is gone, with the shafts in you can spin them and get the noise and clearly see the spider gears making this sound.


Anyhow I have some options, but Im a bit hesitant for I have the NP242 which is why I went selectable on the rear locker.

What do you guys think about a front spartan locker or a true trac for options?
Im not looking to spend selectable$$$$ again on a D30.
or i could keep it cheap and just replace the spiders i guess.
I understand when in fulltime 4x4 i would have to leave the rear unlocked as to not grenade the TC

 

A Spartan locker works fine in the front with an np242, it will steer a little different if you use full time on the street but I never used full time anyway so that wasn't a problem for me.

 

The rear doesn't effect the NP242 full-time usage. I've read both sides of the Full-time issue with a lunchbox up front and I decided to toss a matching Aussie in the D30 when I regeared since I don't need full time much if at all anymore.

 

I've been running a TrueTrac in my front axle with the 242 for a couple of years now. It handles just fine. No issues. It handles mixed snow/wet/dry road conditions better with the TrueTrac than it did with open diff.

 

All I know is 4full is supposed have give 30/70 split in it's power distribution. The 4low/ part time lock the tc diff to be 50/50 output I believe.
More importantly full time is supposed to allow slippage which is where I wonder if a true Trac is a good option. Not sure I wanna here the Spartan clicking lol, the worn spiders drove me nuts already. As for which axle slips I'm not sure it matters in full time, correct me if I'm wrong, but I think it just needs the ability to slip.

 

The full time is just an open differential, so that would be a 50/50 split, part time locks the front and rear driveshafts together to turn at the same speed. What ever kind of differential (locker, limited slip, open) you have in the front or rear axle has no affect on how the transfer case operates.

 

Are you certain, I think for this TC you might have that backwards?

 

It's actually 48/52; the front gets just enough so that it can't out-rotate the rear while turning. Full time is no different from part time except for the torque bias, that's it.

 

An open differential is a 50/50 torque split meaning both sides will always get the same torque, that doesn't mean both wheels or (output shafts in this case) will spin at the same speed. For example if you have an open differential in the rear axle and you lift one tire off of the ground on a stand only that tire will spin since energy takes the path of least resistance, but the tire on the ground that isn't moving is still getting the same amount of torque which is very little since it takes very little torque to spin a tire in the air. If the differential is locked, both axles will spin at the same speed regardless of the torque on each axle, so in the previous example if the differential was locked all the torque would go to the wheel on the ground since that is the only wheel with traction and the vehicle would drive off of the jack stand. Same goes for the transfer case, full time is an open differential with a 48/52 torque split in this case which is mainly due to how power has to make a 180 to go out the front output shaft so it receives slightly less torque. If you put the rear of the vehicle on jack stands and put it in full time, only the rear tires will spin since their is not enough torque going to the front tires to pull the vehicle off of the stands, as soon as you put it in part time the front tires will pull it right off of the stands since the front and rear axles are now locked to spin at the same speed regardless of torque.

 

That says it better lol

 

Ok now we are deffinetly on the same page, however this is where I thought the fulltime wasn't a function where you would want front and rear locked, or would this essentially default the tc to a part time mode? Or yet again if front and rear are locked in full time, are you simply not getting the torque applied to the front locked axle?

 

Full time would still work the same way with the front an rear axles locked. In full time you have 3 differentials, one in each axle and one in the transfer case, with the axles locked the transfer case differential would still be able to vary speeds between the front and rear axles. Part time locks the transfer case so both driveshafts spin at the same speed just like a locked axle will make both wheels spin at the same speed.

 

Thank you, I really appreciate your patience here, I've had this burned into my head before I bought my rear locker, apparently some one was quite mistaken.

Is it fair to say running front and rear locked in full time would have no adverse effects, other than the obvious front/rear diffs not being open? For instance snow driving may not be preferable when locked.

Does anyone running a true Trac like how it grabs, if I did it again I would have locked the front for sure.

Perhaps a Detroit or grizzly is a better option when not in use?