Broken VC

[Aeroking]

I've come to the conclusion that i have a broken viscous in the transfer case.

Lately, gotten vibrations at highway speeds when i let off the gas, and driving around, i notice the front tires skip and squeel. And the accelleration trickles at high rpms.

My truck is now garaged for the winter, but i have dyno time available coming up.

If the VC is bad, and i disconnect the front driveshaft for the dyno, would the broken viscous affect the rear differential performance?

 

[TYTILIDIE]

Re: Broken VC

I've come to the conclusion that i have a broken viscous in the transfer case.

Lately, gotten vibrations at highway speeds when i let off the gas, and driving around, i notice the front tires skip and squeel. And the accelleration trickles at high rpms.

My truck is now garaged for the winter, but i have dyno time available coming up.

If the VC is bad, and i disconnect the front driveshaft for the dyno, would the broken viscous affect the rear differential performance?

No.

 

[dgoodhue]

Re: Broken VC

While you have the front prop shaft is out, you can also check to see if the VC is locked.

 

[Aeroking]

Re: Broken VC

While you have the front prop shaft is out, you can also check to see if the VC is locked.

right now i have to put the truck in neutral and jack the rear tires up to spin the propshaft when i take the bolts off.

 

[dgoodhue]

Re: Broken VC

right now i have to put the truck in neutral and jack the rear tires up to spin the propshaft when i take the bolts off.

You mostly have to do that with most trucks with a working VC anyways, it normally slips at about 50ft-lbs. (not sure exact numbers) DaveP has a write up on the torque spec to check the VC with a torque wrench that is very helpful.

 

['JustDreamin']

Re: Broken VC

And the truck won't move with the front propshaft removed.

Under its own power.


But park it on a hill without setting the parking brake and it will move all by itself (gravity works).

'JustDreamin'

 

[STEVECUL8ER]

Re: Broken VC

Here's the torque test, abbreviated version:

Trans in neutral.
Rear output locked so it can't turn. (Bar through u-joint pushed against floor or frame is fine).
Torque wrench on nut on front output yoke.
Turn front output CW with torque wrench.

At 40ft lbs, it should take 10-12 seconds to turn yoke 90º.

If you can't turn it at all it's locked. Replace it.
If the torque falls off to well below 40 after a few degrees, it's failed 'open'. This won't break parts like the locked will, but you won't have the full benefits of AWD. And the truck won't move with the front propshaft removed.

DD and did the test and couldn't turn the nut on the yoke-didn't even move the rear prop shaft.Does this mean VC is definetly toast ? Could there also be problems with the planetary?

 

[Aeroking]

Re: Broken VC

Thanks Dave

Ran the test and mine turned out ok. I noticed i broke the driverside CV shaft though. lol 2000 miles, and the boots are shredded, big mess.

 

['JustDreamin']

Re: Broken VC

DD and did the test and couldn't turn the nut on the yoke-didn't even move the rear prop shaft.Does this mean VC is definetly toast ? Could there also be problems with the planetary?

Are you sure you did the test right? You're supposed to lock the rear output, with the trans in neutral, and attempt to spin the front shaft? Just trying to clarify that it was done correctly.

'JustDreamin'

 

[STEVECUL8ER]

Re: Broken VC

rear driveshaft disconnected at rear axle.
trans in neutral
socket on nut (looking from front of vehicle to rear) turning clockwise----
no movement at all at over 100 ft lbs
the rear propeller shaft did't even budge.
Anyway need the truck back on road so both shafts put back in service so I could still drive to work etc.
Thanks for input

 

[Aeroking]

Re: Broken VC

rear driveshaft disconnected at rear axle.
trans in neutral
socket on nut (looking from front of vehicle to rear) turning clockwise----
no movement at all at over 100 ft lbs
the rear propeller shaft did't even budge.
Anyway need the truck back on road so both shafts put back in service so I could still drive to work etc.
Thanks for input

you're supposed to lock the transfer case output by leaving the driveshaft connected, and keeping the rear wheels stationery. This forces the Viscous to slip at a force of 40ft/lbs. If you disconnect the rear driveshaft, then your not forcing the Viscous to work.

 

['JustDreamin']

Re: Broken VC

rear driveshaft disconnected at rear axle.
trans in neutral
socket on nut (looking from front of vehicle to rear) turning clockwise----
no movement at all at over 100 ft lbs
the rear propeller shaft did't even budge.
Anyway need the truck back on road so both shafts put back in service so I could still drive to work etc.
Thanks for input

So, trans is in neutral. That's Good.

Let me get this straight. The rear output shaft is disconnected completely, you're applying torque to the front output shaft, and you get no movement at all at 100 ft lbs? That's fubar, 'cause everything should be spinning freely if the trans is indeed in neutral and you're not holding the rear shaft. If that's the case, the truck should barely move under power. Now if the rear is LOCKED IN PLACE and you're applying 100 ft lbs to the front input and it doesn't move, then yes, your VC is cooked.

'JustDreamin'

 

[MIXEDBREED]

Re: Broken VC

If the vc fries locked and breaks the front diff and you are only rwd does that mean you are pretty much only using 65 percent of the trucks power. Cause with miy front diff broke and vc cooked I still out ran my buddys lighting lol.

 

['JustDreamin']

Re: Broken VC

If the vc fries locked and breaks the front diff and you are only rwd does that mean you are pretty much only using 65 percent of the trucks power. Cause with miy front diff broke and vc cooked I still out ran my buddys lighting lol.

If the VC is locked solid, and the front diff (or any other portion of the front drivetrain) is broke / missing / etc, all of the power will go to the rear.

'JustDreamin'

 

[Aeroking]

Re: Broken VC

if you think you only have RWD, look in your mirror, and see if your fishtailing. You'll know.

 

[STEVECUL8ER]

Re: Broken VC

So, trans is in neutral. That's Good.

Let me get this straight. The rear output shaft is disconnected completely, you're applying torque to the front output shaft, and you get no movement at all at 100 ft lbs? That's fubar, 'cause everything should be spinning freely if the trans is indeed in neutral and you're not holding the rear shaft. If that's the case, the truck should barely move under power. Now if the rear is LOCKED IN PLACE and you're applying 100 ft lbs to the front input and it doesn't move, then yes, your VC is cooked.

'JustDreamin'

The rear drive shaft was disconnected at the rear end. Maybe I just didn't wait long enough for the torque to "slip". I just turned it for 1 or 2 seconds. The truck drives the same since I had it for the last 70,000 mi.IDK

 

[STEVECUL8ER]

Re: Broken VC

The rear drive shaft was disconnected at the rear end. Maybe I just didn't wait long enough for the torque to "slip". I just turned it for 1 or 2 seconds. The truck drives the same since I had it for the last 70,000 mi.IDK

OK. Jacked up truck and removed the front prop,put in neutral,put screwdriver thru the u-joint-put about100 lbs of torque on the nut-held on for about 30-40 seconds and the clutch finally started to slip but it moved I say 10 degrees. Verdict?

 

[Ryan Heller]

Re: Broken VC

That is almost the same thing mine was doing i would say the VC is junk that is what every one keeps telling me about mine i just ordered a new one with a bearing and seal kit total was 406 to my door
Good luck

 

[STEVECUL8ER]

Re: Broken VC

That is almost the same thing mine was doing i would say the VC is junk that is what every one keeps telling me about mine i just ordered a new one with a bearing and seal kit total was 406 to my door
Good luck

When you get it fix and test it out that the vc was the problem.let me know.

 

[Ryan Heller]

Re: Broken VC

Will do :tup: