# Grinding when shifting from 2WD to 4WD



## 91NissySE (Jan 13, 2009)

I have 91 Nissan Truck with auto locking hubs. Today when i tried to shift into 4hi, i would get this horrible grinding noise. I placed the shifter back in 2wd and i had a rattling/grinding until i slowed down to 5mph, then it seemed to disengage. The truck has about 137,000mi on it and no maintenance has been done to my knowledge. I was wondering about the linkage going to the transfercase....? I dont think the auto hubs have ever been re-packed. Any suggestions to get the 4wd working again? As more money is allowed, im going to start working on preventative maintenance stuff. 
Any advice will be appreciated
Thanks


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## dvdswanson (Nov 6, 2005)

get rid of the auto hubs! seriously, if you like auto hubs, clean them up and regrease them, you may need to replace the springs also. I've always used manual hubs, reliable easy and dont cause problems, but autos are fine.

I would also suggest changing the fluids in the tranny and t/case. do you have an auto tranny or 5 sp.? 

grinding is most likely due to lack of care.


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## 91NissySE (Jan 13, 2009)

Well my girlfriend, now my wife bought the truck with 80,000 on it. The truck was previously owned by another girl, who didnt even change the motor oil. After my wife bought it in '98, a week later, the engine blew. Another engine was installed and got its oil changed on a regular basis. Other than that, that was all that was done. Now the truck is in my hands. I will check the fluid levels in the transfer case and i will look into the hubs. It seemed as though the transfer case was grinding right as i was trying to put it into 4WD. The tranny is an automatic, which hasnt been touched either.


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## dvdswanson (Nov 6, 2005)

yeah, change the fluids, if you put the tranny in park there shouldnt be any grinding, but if it is in neutral, the tranny will free spin a little, it will go into 4 WD but you may have a little grinding, use force if you have to in 4LO.


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## 91NissySE (Jan 13, 2009)

Tuesday it should warm up and i'll change it, its 3 degrees out now. Yesterday, when i was at a dead stop, there was some little grinding in park. I shut the truck off and made sure the t-case was in 2H. Everything seemed to be disengaged. Im ordering a shop manual for this truck so that i can understand things better.


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## hans747 (Jul 14, 2005)

3 degrees, huh? That might part of the problem, along with that ancient fluid. I have a 2wd with a manual tranny. When it gets that cold, I have to let the truck idle for a few minutes otherwise just getting into gear is a grindfest. The gear oil starts to turn to pudding at those temperatures. Fortunately, I can just pull the parking brake, put it in neutral, let out the clutch, and the there's still enough spinning in the transmission to warm things up. But to give you an idea of what cold gear oil is like: when I start the engine on cold mornings, it idles at about 1200 rpm. When I put in neutral and let the clutch out, the RPMs get dragged down to 800rpm. There's THAT much resistance hiding in that cold fluid. The problem for you is that there's no way to warm up the Tcase without actually moving the vehicle. So if you need FWD to get out of the neighborhood, you might have some problems.

Put some good oil in there, and things might clear up a bit. Save the old Tcase fluid and donate it to a museum.


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## 91NissySE (Jan 13, 2009)

Well yesterday, i changed the T-case fluid and there were some slight signs of some metal residue..nothing major. Went out to test drive four wheel drive senerio, and shifting from 2H to 4H did require a little effort. Once the hubs were engaged, i could shift from 4H to 2H and back again with two fingers. I back up, disengaged the hubs and then shifted back into 4H, and i had to use some effort again. Didnt hear any grinding though. Seems that the only time the t-case grinding is the first couple of times then it goes away...maybe an outside temperature thing. I'll play with it today. Any comments......?


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## dvdswanson (Nov 6, 2005)

where you in park or neutral?


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## 91NissySE (Jan 13, 2009)

> dvdswanson where you in park or neutral?


I was in drive the whole time when i was shifting from 2H to 4H. When everything is dis-engaged (and driving down the road) and i place the t-case in 4H, it requires a little effort. Then still driving foward, i can place the shifter from 4H to 2H and back with no effort at all. Then i stopped the truck, reversed to unlock the hubs, and drove off again. Now everything is disengaged again, so i went from 2H to 4H and it took some effort. Once all hubs are locked in, i can shift from 4H to 2H and back again with no effort. none of this is done in park or neutral.....i hope this makes sense.


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## dvdswanson (Nov 6, 2005)

your system is NOT a true shift-on-the-fly system. when shifting between 2 and 4WD you should be below 20 mph, stopped would be best. once the hubs are locked, everything is moving at the same speed allowing easy shifting. try it with park or neutral, not in gear, and see how it shifts.


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## 91NissySE (Jan 13, 2009)

Thanks Dvdswanson....when i was first wondering about the grinding, i was underneath looking at the shifting linkage. My wife started the truck and we moved the shifter back and forth from 2H all the way to 4Lo while running in neutral. So everything works good. Im used to shift on the fly 4wd setups, so this is new to me. This is a dumbarse question or rumor, but i heard that it take a while for the new t-case fluid to "break in", is this true? ....soon i'll be on to tearing apart the hubs once i get the shop manual. 
thanks for all the replies....


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## dvdswanson (Nov 6, 2005)

break-in period refers to physical parts, gears, etc., like a new car you want to give it time. fluid just flows, when its cold its thicker so it flows slower. but there is no "break-in" for fluid. I would suggest changing all the fluids as well if it hasnt been done in a while.


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