[WubangerMac]

I noticed the other day when I was getting my 78 bronco inspected that the front drive shaft was turning while on the dyno. the truck was in 2 wheel drive and the hubs were not locked in. My transfer case does chatter a bit while I am driving. with the truck stopped, the front drive shaft turns freely.
Is this normal or is my transer case worn out. I have a np205 with a c6 auto.

thanks.

 

[JB]

my 95 with a BW1356 does this as well. it happens all the time when its cold out. when its warm or after ive been driving it for a while it quits. i notice it now because the d-shaft is unbalanced and i get a little bit of vibration. its normal

 

[fartman]

I dont think its normal for the front Dshaft to be turning in 2wd.

 

[Bronco4Life]

my 95 with a BW1356 does this as well. it happens all the time when its cold out. when its warm or after ive been driving it for a while it quits. i notice it now because the d-shaft is unbalanced and i get a little bit of vibration. its normal

No JB... :rofl:

Definitely not normal.

 

[ftwdeviant1]

I've seen this on pretty much every 4x4 that i've seen I dont know why but is normal just make sure you spin the drive shaft by hand

 

[waltman]

No it is not normal

 

[Hoxviii]

Yes and no. it's not normal for it to spin at full speed, but on a 205 the lube in the case can create a fluid drive between the rear output and the front output.

put teh truck in 2wd adn see if you can spin teh shaft by hand (truck off, hubs unlocked). if so, start the truck and see if the shaft starts to spin a little. it it does, you'll be able to grab it (i'm NOT recommending this) and stop it, let go and it may pick back up.

Same concept as how if you have a manual transmission if it's cold enough out you can stop with the clutch in (in good working order) and the vehicle will still try to creep forward just a little bit.

Justin

 

[GTRider245]

Yes and no. it's not normal for it to spin at full speed, but on a 205 the lube in the case can create a fluid drive between the rear output and the front output.

put teh truck in 2wd adn see if you can spin teh shaft by hand (truck off, hubs unlocked). if so, start the truck and see if the shaft starts to spin a little. it it does, you'll be able to grab it (i'm NOT recommending this) and stop it, let go and it may pick back up.

Same concept as how if you have a manual transmission if it's cold enough out you can stop with the clutch in (in good working order) and the vehicle will still try to creep forward just a little bit.

Justin

Thats interesting...

But I would say for our trucks, no. There is no reason the front shaft should be moving at all if the truck is in 2WD.

 

[Hoxviii]

Thats interesting...

But I would say for our trucks, no. There is no reason the front shaft should be moving at all if the truck is in 2WD.

It's a really common phenomenon in all lube bath power transmission systems. Ever seen a tractor PTO spin even though it's not locked in? Same idea.

It's also possible for a chain driven case to do it some as well. the rear output spins, spins the fluid, which will then cause the gear the chain is hooked to to spin, which will then cause the front output to spin.

Again, it won't be full speed and if you grab it it'll stop moving since it's not mechanically locked in. I had a 208 (before i killed it and swapped the 205) that would do it if it was below freezing in my last truck.

Justin

 

[Robs79BBbronco]

it's normal.opc1:

 

[Hoxviii]

Not normal, but not uncommon. So long as it's not making any goofy noises and isn't actually locked in don't worry about it.

Justin

 

[JB]

No JB... :rofl:

Definitely not normal.

you obviously havent seen many older ford 4x4's, cause MOST of the ones ive seen will do it.

it not like its spinning like hell, it barely turns. ive seen it discussed here before and im pretty sure its due to the viscosity of the oil.

 

[Fireguy50]

I vote normal. It's just rotational force moving the xcase fluid, which barely moves the chain, which will turn the front shaft, if the front hubs are unlocked.

 

[bigblockbuggy]

Normal, even my brand new Atlas II does it. It is all due to the oil viscosity, and it happens in nearly any type of gear train. An auto trans will do it as well in neutral with no load on the output (i.e. no drive shafts, or t-case in neutral as well)

It is possible that the folks in much warmer climates never see it as the oil viscosity is lower at higher temperatures.

Later,
Jason