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NP242 question - differential in 4 FT mode vs 4H PT mode, turning by hand

ANZAC_1915

NAXJA Forum User
Location
Redmond WA
I've just rebuilt my 242.

I haven't put it back in the car yet, but I'm wondering if you should be able to turn the rear output and front output flanges at different rates (like an open axle) by hand in 4H Full time mode.

All of the modes seem correct, but at least by hand, 4H FT feels just like 4H PT.

When I built it I confirmed the differential component by itself spun ok.
I checked the basic operation of the sector/forks etc before I buttoned it up but without a top case everything is a bit wobbly and it seems impossible to tell if it is working correctly.

I am thinking there are two possibilities:

1) because it doesn't have oil yet, it isn't crazy about shifting into 4H FT and maybe the shift fork/sleeve is stuck (fork shaft is spring loaded). It cycles through all the other modes fine. Maybe things will work one there is oil in it and I drive it and warm it up and cycle it a bit through the shift pattern.

2) the TC is working fine; but you can't turn them by hand, because the ratio of the diff gears is high enough you need more torque difference across both outputs to get them to move at different rates

I'm not interested in your theory or opinion re #2, I'm interested if you have been physically able or not able to spin the differential of a complete 242 out of the vehicle.
 
They should spin independently. You should be able to turn the rear without turning the front and vice versa.

Make sure everything is bolted down snug, including the yoke. If there's any looseness, the internal parts will shift around instead of making the shifters move
 
They should spin independently. You should be able to turn the rear without turning the front and vice versa.

Make sure everything is bolted down snug, including the yoke. If there's any looseness, the internal parts will shift around instead of making the shifters move

Everything is snug. The fork is able to select the locked (4H PT) and open (2H) modes.
 
Have you tried using a bit more force to turn the yokes? Have a buddy hold one yoke while you try to spin the other?

Have not, planning to do that Saturday.

I don't really want to crack the case again if this is normal behavior.

But then I also don't want to have to install and remove it if this turns out to be an issue.
 
They should spin independently. You should be able to turn the rear without turning the front and vice versa.

Make sure everything is bolted down snug, including the yoke. If there's any looseness, the internal parts will shift around instead of making the shifters move

Have you spun them by hand on a 242 on your bench?
 


One thing to check is if the long shifter rod is able to move freely. If it binds up then the mode arm at the differential won't move all the way either. I've seen them bind up on the output housing, sometimes they are too long or the aftermarket housings aren't machined correctly.
 
Thanks. I did notice the shifter rail had to be pulled a little anti-clockwise (on the output housing rotation) to get everything buttoned up. And now that I think about that.... how can it possibly slide up and down if it is under side tension?

Maybe I'll just take the output housing and flange off and see if that frees things up, I should also be able to see what the shift rail and sleeve are doing.

(BTW this is a Tom Woods SYE housing, so maybe there's something hinky. I can probably dry fit the old housing to check too)

One other question I had is, which order/direction are each of the positions lowest to highest (I should have looked while it was open).

e.g. Disconnected (2H), Locked (4H PT), Diff (4H FT)?
 


One thing to check is if the long shifter rod is able to move freely. If it binds up then the mode arm at the differential won't move all the way either. I've seen them bind up on the output housing, sometimes they are too long or the aftermarket housings aren't machined correctly.

Oh your video was really helpful. The front and rear outputs on my TC are also in locked mode in neutral, but disconnected from input (wasn't sure if that was by design). The front output is disconnected in 2H.

Back to the drawing board!!
 
I had to move the little bushing / sleeve out of the stock housing and into the AA housing to help the rod end slide. Also some of the older tcases have long shafts that will make contact with the plug that goes over the end, and you will have to cut the end of the rod for those to work. If you have not downloaded and printed the instructions yet you should
 
When I unbolted the output housing the shifter dropped into place. It is the sleeve piece (from the upper fork) not the shaft itself that is binding. I'll have to take a look at the alignment of the output housing.

Unfortunately a can feel a tiny little bit of binding when I spin the now freed differential. I am not sure if it is the gears or the shift collar just nibbling on the splines. May need to crack the case too. :(

Anyway, thanks for the advice.
 
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