I have a 2nd gen 97 blazer that will not engage the front axles. I will try to keep a clear description.
1. dash switches indicate changes from 2hi to 4hi and 4lo and back again.
2. the vacuum actuator pulls in and the cable freely moves.
3 When you loosen the cable retaining nut on the differential and pull the cable, it pulls freely but doesn't seem to do much.
4. when you turn one wheel/axle the other does not move.
I am making the assumption that some thing is not connected or broken in the front differential. Can it be easily repaired?
I may have access to a 2000 Blazer, some type of special edition. 4.3 automatic. bad engine. Can I swap the front differential to the 97?
Could I put the 97 engine, (runs good- 60k miles), in the 2000 Blazer. I would appreciate helpful information from you knowledgeable folks, Thank you.

 

Raise only the right front tire off the ground. With the engine at idle, transmission in park or neutral, select 4HI. The right front wheel should not turn by hand. Select 2HI, and the right front tire should immediately turn freely by hand. Post your results.

 

At idle, in park, right front wheel raised, spins freely in 2hi and in 4hi.

 

Make sure the actuator under the battery tray is getting good strong manifold vacuum when 4WD is selected, and no vacuum in 2WD. If not, trace the vacuum line back to the vacuum switch, look for holes etc in the line. Make sure one of the lines on the vacuum switch has good strong manifold vacuum when the engine is at idle.


If the vacuum system checks out OK, next is the shift mechanism in the front right axle tube. When you pull on the cable, the right front wheel has to lock up.

 

15 " vac at the actuator at idle, seems to pull the cable but nothing. If I pull the cable housing loose/off will I be able to see the fork or coupling sleeve?

 

It's going to require a certain amount of disassembly to diagnose & repair the problem. You aren't going to be able to see much without removing the axle tube. Can't hurt to remove the housing that the cable goes through, and make sure it's still connected to the fork. Or maybe the cable is broken. A visual inspection will find the problem. If you need an exploded view, let me know and I can post it.

 

Thank you for the video, wish mine was that clean. The exploded view will be helpful, thank you. one other question, my vacuum line to the actuator is a lot smaller than the one in the video, maybe 3/16" id. runs to a splice tub at the fender well on a similar size tube. could it be too small?

 

The vacuum line diameter is not all that critical, 3/16" is fine, just make sure it doesn't leak, and that it's not kinked.

 

Thanks again for your assistance. On the 2000 blazer front differential, is it a direct replacement? How can I tell the gear ratio of the units ? I believe GM used 3.43 and 3.73 ratios. Is there a year or model distinction for the ratios? When I get this figured out I will post the findings. Thanks again.

 

RPO codes in the glove box will tell what gear ratio you have. Post the ones that start with "G" and we can figure out what you have. ZR2 differentials are different from non ZR2. Ratios are 3.42:1 and 3.73:1, and came with either open or limited slip configuration.