Trouble shooting 4WD from the warmth of my living room.

[fatherdoug]

I am starting to get a noise from underneath the truck when the truck is put in 4WD. It almost sounds like a fan blade rubbing on a shroud and is speed affected to a certain point.

Here are the symptoms: '78 Ford F-150 NP205 Transfer case(Part Time)

Hubs out: no noise

Hubs in: no noise

Hubs in, 4WD engaged: noise up to about 20 mph, then ceases. Noise interval increases with speed up to about 20 mph.



Here is my understanding of what goes on when hubs are in or out:

Engaging the hubs connects the axle shafts to the differential.(Axle shafts turn) Does the front driveline also turn when just the hubs are engaged, or does engaging the 4WD allow the driveline to connect to the transfer case?


I'm thinking the noise is in the U joints of the front driveline. There is a little play in those U joints. I already have the U joints, but am waiting for warmer weather to replace.

 

[m78]

Originally there were metal dust covers at the end of the axle tubes, just inside the u joint.
If your's are still there, they could be getting ready to fall off.

 

[fatherdoug]

Thank you, Mark. I'll take a look at those. I know they were tight with no signs of degradation when I replaced the hubs aboot 5? years ago.

 

[Beach66Bum]

Morning Doug,
when you lock in the front hubs, the front driveshaft will turn but it is still not being powered by the transfer case till you use the 4WD lever in the cab to engage. X2 to what Mark replied. Lift up the front end and put jack stands under. Then you can check the front drivetrain by locking in the hubs and turning the front wheels by hand (place the transfer case in the neutral position) you will be able to see and hear any problems.

 

[fatherdoug]

Thank you Roy. Good advice. Will have to wait until it warms up, but I will try that.

 

[m78]

By the time it warms up the ice thats built up against the dust shield and uj's will have melted and the noise will be gone.

 

[fatherdoug]

By the time it warms up the ice thats built up against the dust shield and uj's will have melted and the noise will be gone.

I REALLY hope you are right!

 

[Sparky83]

would give the driveshaft a little shake laterally to see if it moves.. when the ujoints start to really go theyll give off like a metal shaving sound. if it moves up/down left/right would get to replacing them. spin yes.. movements like that no.

 

[fatherdoug]

There is a tiny bit of lateral movement, which I noticed earlier this fall, hence the purchase of said U joints. This will be an outside job, and it has warmed up to -1 today. Thank you, Shawn.

 

[m78]

I thought you guys up north were used to that cold and just lay on the ground in the slush to work on your trucks.

 

[Sparky83]

There is a tiny bit of lateral movement, which I noticed earlier this fall, hence the purchase of said U joints. This will be an outside job, and it has warmed up to -1 today. Thank you, Shawn.

your welcome mate.. and know the feeling... i have a garage but never get to work on things in there... plus the trucks too wide to fit in there lol

I thought you guys up north were used to that cold and just lay on the ground in the slush to work on your trucks.

hehe hes getting old mark... you know how them old timers get when it gets cold.. they feel cold in the summer heat and even more in the winter...

 

[DNFXDLI]

Check your slip joint and ujoints in the front driveshaft as well Doug...make sure there is no bind on it when you check it...as in transfer case in neutral and hubs unlocked

 

[fatherdoug]

I thought you guys up north were used to that cold and just lay on the ground in the slush to work on your trucks.

The only time I lay in the snow is to listen for trains........

 

[fatherdoug]

Check your slip joint and ujoints in the front driveshaft as well Doug...make sure there is no bind on it when you check it...as in transfer case in neutral and hubs unlocked

Slip joint seems to be okay, as in no binding, but there is some up/down slop in the slip joint. Is that normal?

 

[Sparky83]

Slip joint seems to be okay, as in no binding, but there is some up/down slop in the slip joint. Is that normal?

slip-joint so long as its minute is ok.. sometimes repacking the grease can help there too.. if you get major movement then would start looking for new driveshaft

 

[DNFXDLI]

There should really be no play in the slip joint....I check my 350 and 750 yearly....zero lateral movement

 

[fatherdoug]

Thank you, Duncan.

 

[fatherdoug]

Question. Can one just replace the slip joint? I can find a slip joint replacement, but I'm having a hard time finding a front driveshaft for a NP205 with auto tranny and a 133" wheelbase that does NOT have a CV joint.
'

 

[DNFXDLI]

No...you either have to find an NOS one or take it in to a driveline shop to get new ones welded on and balanced.



I believe the ones from you truck and mine all have a double cardan joint in them....pretty sure the intermediate carrier of the u-joints is a service item.


Edit...I've never looked into purchasing a premade aftermarket one....I don't know if they would be a stock item...I'm basing what I know on my own experience

 

[fatherdoug]

No...you either have to find an NOS one or take it in to a driveline shop to get new ones welded on and balanced.



I believe the ones from you truck and mine all have a double cardan joint in them....pretty sure the intermediate carrier of the u-joints is a service item.


Edit...I've never looked into purchasing a premade aftermarket one....I don't know if they would be a stock item...I'm basing what I know on my own experience

That's the problem, Duncan. My front driveshaft does not have a double cardan U joint (CV). I think they started that in '79.

Bronco Graveyard sells just the slip joint, but I don't want to use it if there is a balancing problem.

My '79, new, had the double cardan U joint.