Can I drive my Astro Van AWD without the front drive shaft?

[peppy]

Well, I finally was able to reconnect the front driveshaft...and its defeinite, the viscous clutch in the transfer case is toast! Now, I have to find another transfer case at the local junk yard. I will update once I take the next step...

Peppy!

[peppy]

I was thinking of converting to true 4x4 by putting in a front differential from an S10 blazer that has the locking mechanism.

What do you think?

[LiftedAWDAstro]

It isn't the front diff that makes the van a true 4x4. It is the transfer case. You need to install a NP231C 2 speed transfer case in order to make the van have selectable 4WD.There are stickied threads in the AWD/4x4 section.

[peppy]

I guess I should explain what I mean. Ok, at this point it seems 100% definite that the viscous clutch in the transfer case has seized. Basically, this means that the transfer case transfers 100% torque to the rear AND to the front! With the front drive shaft off, the torque only goes to the rear. If I put my front drive shaft back, the torque will now be transferred to the front as well, making it a 4x4 vehicle, where ALL FOUR wheels are receiving torque from the transfer case. Not a good thing, unless you are on snow, or only need the 4x4 to get out of a stuck position - say mud or trench. However, by putting in a front differential from the S10 that you can lock and unlock, you have selection. When its locked, you have 4x4. When its unlocked, the torque is only transmitted to the rear. When its unlocked, the front drive shaft does turn, but since the front diff is unlocked, the drive shafts get no troque. With the viscous clutch seized and the front lock/unlock differential, you have 2WD and 4WD Hi. I guess if you want 4x4 Low, then you need to swap the transfer case. Can someone explain to me the usefulness of 4WD low?

Peppy.

P.S. Basically, the seized viscous clutch has caused the AWD to turn into 4X4! You dont want full time 4X4! That will sooner or later, but probably sooner, damage some drive parts. When the viscous clutch is working properly, the transfer case is NOT transmitting any torque to the front! It is only transmitting torque to the rear. However, when the rear wheels begin to slip, the viscous clutch starts to transmit torque to the front, to give you extra traction. Thats how AWD works.

[peppy]

Basically, a seized viscous clutch in a BW4472 transfer case makes the vehicle a 4X4. And, thus a lockable front diff makes it possible to change from 2WD to 4WD. However, in a properly working BW4472, you DONT want to have a front diff that is unlocked. That will cause the viscous clutch to seize! (I guess if you want a seized viscous clutch, that would be a way of doing it!)

Peppy

[LiftedAWDAstro]

If your t-case is bad, fix or replace it. The fix isn't to swap to a different front differential.

The advantage to low range is for lower speed crawling along a really rough trail or rock garden. It basically triples the torque output of the motor. This give you much better control of the speed at which you go over things as well as allows you to use less throttle to do the same work.

[mdmead]

If your t-case is bad, fix or replace it. The fix isn't to swap to a different front differential.

I agree this isn't the ideal solution, but in theory it should work. With a locked up AWD t-case, you would always be sending power forward, so you would need some kind of "relief valve" when the front tires were turning at different speeds (during cornering). By adding an S-10 diff/axle with a posi-lock, when unlocked, the relief would come by sending power to the disconnected axle side.

But like Dean, I'd suggest either replacing the broke t-case with a working AWD unit or a 2-speed model. A working AWD viscous case is so close to true 4wd that it will serve you well 99% of the time. That other 1% is probably when you would be better off with low-range as well. My guess is the cost of a S-10 axle with a posi-lock isn't going to be any cheaper than a used viscous t-case if you do a junkyard search via http://www.car-part.com

[peppy]

Its simply an option.

By the way, I checked the price for a transfer case on http://www.car-part.com and cheapest is about $500.00

But, I can get the necessary parts from the front differential - remember, only the right tube and axle are needed, for less
than $20 at a local junk yard.

Peppy...

[peppy]

How do you know whether the replacement transfer case has an operational viscous clutch?

[mdmead]

Its simply an option.

By the way, I checked the price for a transfer case on http://www.car-part.com and cheapest is about $500.00

But, I can get the necessary parts from the front differential - remember, only the right tube and axle are needed, for less
than $20 at a local junk yard.

Peppy...

Wow, I just checked the Pacific Region and found them (t-case) as low as $150.

And remember, if you replace the axle tube, you will need to operate the axle sleeve which means you will need a Posi-Lock (added $) or adapt the iffy vacuum system the factory used.

[peppy]

Why are you so against the front diff being swapped? You dont like the foreign part?

Take it easy, let the force of possibility do its thing!

Peppy!

[mdmead]

Why are you so against the front diff being swapped? You dont like the foreign part?

Take it easy, let the force of possibility do its thing!

Peppy!

Whatever dude.

[LiftedAWDAstro]

Peppy...what Matt is saying is that once you swap the front axle disconnect parts from an S-10 into your van, how are you going to actuate the disconnect mechanism? If you don't build a cable locker or install a Posi-Lok setup ($200) the front diff will be USELESS!

[LiftedAWDAstro]

Its simply an option.

By the way, I checked the price for a transfer case on http://www.car-part.com and cheapest is about $500.00

But, I can get the necessary parts from the front differential - remember, only the right tube and axle are needed, for less
than $20 at a local junk yard.

Peppy...

Why not post here in the "Wanted" section here for a BW4472 transfer case? You should be able to get one for between $100 and $200 shipped.

The other option is to source a NP231C transfer case from a similar year S-10. This will fix 2 different issues. You will replace the bad transfer case and you will get the option of having 2WD high, 4WD high, Neutral and 4WD low. Then you can do the front diff with a manual locking mechanism and you can have 2WD Low range for backing trailers up, moving around the yard and stuff like that. You can get a NP231C t-case off E-bay for between $50 and $150.

[peppy]

So, In the meanwhile I can put in an S10 front diff, and when I have time, fix the transfer case? or put in the NP231C?

What a great idea!

I should have thought of that myself!

Peppy!