I was plowing this morning and my 4wd quit again
I thought my cable had come loose so i jacked it up and took the plastic housing off but it was still hooked
with it in 4hi I manually pulled the cable but it still wouldn't activate
It sounds like the fork is connected and it does spring back when I let go
Is there anything inside the differential that could be screwed up?
How much work will it be to check

 

Are you sure that the encoder motor is engaging the front driveshaft from the transfer case to the differential?
Put it in 4HI, Do you hear it click? If so, can you manually turn the front drive shaft in PARK?
If you can turn it, then the problem is in the transfer case, either the encoder motor did not shift or something internal.
If it does lock, then you have a problem with the front axle.

So, you did replace the cable? Is the actuator that you connected it to is still pulling the cable in like it should?

If, you say that the fork is okay, then it could be the driven gear on the axle shaft is worn to the point that the collar is not making enough contact to drive the right front wheel.
In that scenario, you are looking at doing a Bravada Axle Swap, or rebuilding the existing front axle. There is a kit for rebuilding that . It has everything to replace the front axle disconnect. It is about $100. That is what I had to do to my CC with 250K miles on it.

Bill

 

I was pulling the cable and engaging it manually
The vacuum actuator got ripped
I was holding the cable with vice grips and it worked for about half a day
how much work is it to repair the front end the way you did it

 

If you have the time, the best way is the Bravada Axle Swap. It gets rid of the vacuum setup and all that crap in the front axle disconnect.
What I did was purchased a Front Axle Disconnect kit and total rebuilt it.
It is alot more work. The next time I have trouble, I am going to find the Bravada Axle shaft and do the swap. Once you do that all your problems go away.
https://www.aam.com/what-we-do/our-products/driveline. This is the company that made the kit.
I got it off EBAY. Don't know if they still have them.


Bill

 

I wonder if the front differential from a 2001 Blazer would fit into the 2001 Jimmy? I might try that this spring. In the meantime I'm thinking maybe put chains on my rear tires to plow with.

 

All S body platforms should be interchangeable. If you are going to all that trouble, you might as well do the Bravada Axle Swap. It would eliminate the vacuum part of the front axle. Just plug up the hoses to and from the transfer case switch. It gets rid of the mechanical in the pumpkin. What it does give you is the right front wheel is engaged all the time like the left front wheel so when you kick it in 4WD you don't have to wait for the vacuum to increase to lock in the right front wheel.
By doing this you also make the system stronger by having one piece to the CV axle shaft instead of two gears, and that shift collar.

This is what I am going to do the next time I have issues.

You can get the Bravada axle for under $100 at the junkyard. Make sure you get and housing for it or you will have to make a delete cover to cover up the shift fork opening to the plastic housing. BTW the plastic housing will go away and the switch gets shorted together.

There is a video on YouTube on how to do that swap..

Goodluck

Bill

 

Here is the info used to purchase the kit I spoke of earlier:

Chevy S10 S15 1997 2004 7.25" IFS Front Axle Disconnect Shifter Kit 4X4 74080003

Don't know if is still made. I got mine in 2018.

Bill