97 Astro Transfer Case Jump

[awdoug97]

Have been given a 97 Astro LS, 165K, body, inside, engine, transmission super condition, transfer case has begun to jump/skip.

No pattern to it, does it uphill, downhill, on level, coasting, turning less than other times, sometimes it is a soft bump, other times hard.

Have done some research and have the following questions in this order.

1. Specs call for Dex tron III transfer case fluid, can I use the new Auto Trak II fluid as I have seen post where this solved the problem on later model years, not sure if I can use it on a 97?

2. Can the AWD mechanism be disabled so it only runs in rear wheel drive (there is no fuse marked on the owners manual that references the control module) as I do not need AWD, only use it for a work van in summer.

Appreciate any information

[Drummernaut]

First I would ask how you know it is the transfer case and not a front or rear differential?

I cannot speak to the type of fluid used in the mechanical AWD transfer cases but I know it cannot be disabled because it is not electronic.

There are lots of discussions of removing the front drive shaft but doing that may cause the van to creep forward when the transmission is in park without a good ebrake. I believe it is the BW4472 that has the possibility of creeping.

If you have trouble with your transfer case, the only option is to rebuild or replace from what I understand.

[awdoug97]

Thanks for the reply.

Many post on the subject on this and other blogs, symptoms point to the transfer case trying to go into AWD when conditions do not require it to do so. Mechanically it could be the transfer case motor, electronically it could be the transfer case module (which controls it), and the wheel sensors which send data that a wheel is spinning, or more precise turning faster than the others.

Agree, not looking to remove the front drive shaft, but rather stop the transfer case motor from engaging the front drive.

There is a lot of speculation about what is causing it, one is always your tires are not all the same, meaning one or more are worn much more than others, this is supposed to cause issues, and your fluid is worn and needs replacement.

Even getting it free cost to repair would probably be in excess of its value.

All in all it seems that in 97 the technology was not up to the task, or maybe they are all that way, even the newer ones.

Thanks again.

Doug

[LiftedAWDAstro]

First I need to clarify some info. Your 97 has a Borg-Warner 4472 transfer case. This is 100% mechanical using a viscous fluid coupling to lock the front output to the rear. They do not lock 100% though so if you do remove the front drive shaft, you must set the parking brake or block the wheels to prevent the van from rolling. The transmission park pawl will not hold it. There is also no speed sendors for the front or rear outputs other than the main VSS on the tail cone. The speed sensor is used by the PCM for transmission shifting, speedometer and ABS programming. As for the fluid to use, I wouldn't use Auto Trac 2 unless it was all you had and you had to drive the van. The regular old Dextron 3 is all you need.

If the transfer case is truly jumping, you will need to have it rebuilt because the chain is what is jumping. The other (cheaper) option is to find a good used one. Before replacing it though, you might want to verify you don't have a differential issue. This is easy to check simply by draining the gear oil out. The front diff has a drain plug. Make sure you have enough 75-90 gear oil on hand before you start though. The rear diff has to have the cover pulled to drain. You are going to need to inspect the oil for metal fines. The rear diff cover can be installed using RTV or a gasket.

[awdoug97]

Thank you, had a feeling that the older ones may be different, especially since there was no fuse associated with the transfer case.

Would have to think any used transfer case would have similar miles on it, so will probably just scrap it or part it out, engine runs strong and quiet.

Appreciate the information.

Thanks, Doug

[LiftedAWDAstro]

You are welcome for the info. Before scrapping it, what shape is the body in? Do you happen to be in a rust-free part of the country? If so there may be interest for a complete vehicle.

[awdoug97]

The van came from Winchester, Va., and is rust free, really the body is in excellent condition, is an LS with all options available at the time, maroon and silver two tone paint, tinted windows, fancy wheels, etc., engine (4.3) run very strong, rear tire very good plus, front okay, some door sticking problems and the timing chain cover gasket is leaking and need replacement, on the whole would rate a 7 or better on a scale of 1 -10, can post some pictures if interested.

Plates are good till end of July so was going to run it back and forth to my workshop which is only a mile away, and to post office.

Will take $800.00 as is, located in north eastern Pa., 17985

Doug

[LiftedAWDAstro]

rear tire very good plus, front okay,

Having worn tires on the front is very bad on the AWD's! That may simply be the issue. If you can find a set of 4 tires that are worn the same and are the same brand and model you would be very wise to replace them. Then for a couple hundred $, swap the t-case with a good used one and have a nice van for cheap!

Other wise, post it up in the for sale section including lots of pics and possibly sell it complete.

[photo_van]

Got a good used transfer case (98,000 miles) for sale- just a short drive to California to pick it up!

[mdmead]

These T-cases can go 250K+ miles, so if you can find one of similar miles or less, I'd go for it. As Dean said, make sure your problem IS the T-case. I'd suspect the rear diff myself, but only because mine crapped out before 100K on my '96.

[awdoug97]

Appreciate the info, I am still having a difficult time getting my mind around that a pair tires worn more than the other two can do damage to the vehicle, but have heard it enough times that while I can accept it, I do not want to own a vehicle that this is a problem, someone had their head somewhere it should not have been.

I have been reluctant to sell it to someone without knowing the issue, the diagnosis and the repairs could be more than it is worth.

Drove it about 40 miles yesterday as had to haul some items to town, figure if it goes just have it towed to salvage yard as that will probably its final resting place. Jumped and kick now and then, but again, no pattern, would think on tight turns it would manifest itself, but not so, just does it almost randomly.

As I said, plates expire end of July so will run it locally till then.

Again, appreciate the input and dialog.

Doug

[Cobra]

it would be a shame to throw away a potentially good van..... I'm guessing by the fact you said Miles in the last post that you aren't in Ontario, Canada....