1990 blazer 4x4 problem

I have a 1990 4x4 blazer. It is a manual on the floor transfer case 4x4 shift with an automatic trans. I put it in 4 wheel high and the 4 wheel drive does not work I put it in 4 wheel low it goes in low but no 4 wheel drive. no funny sounds or anything. What is this about?????

First thing check for the front Axel locking in.
Does the front drive shaft lock in for 4 W drive.
Jack it up on stands and have a look at drive shafts turning.
If both drive shafts turn then check front Axel for locking in.
MT

First thing check for the front Axel locking in.
Does the front drive shaft lock in for 4 W drive.
Jack it up on stands and have a look at drive shafts turning.
If both drive shafts turn then check front Axel for locking in.
MT I fixed a main vacuum hose that was off at the transfer case and hoped for 4 wheel drive but when I put it up on 4 jackstands in 2 wheel drive the driveshaft turns and so do the wheels but in 4 wheel hi and low the driveshaft spins without any problem or noise but the front wheels do not but spin freely by hand.:disappoin

In 4W high or 4Wlow will the front axel lock in.
Turn front drive shaft in 4W and one or both front wheel should turn if it is locking in.

What transfer case does it have?
If floor shift make sure both arms/transfer case shift levers are engaging.

How many positions on shift lever?
And what do they say?

In 4W high or 4Wlow will the front axel lock in.
Turn front drive shaft in 4W and one or both front wheel should turn if it is locking in.

What transfer case does it have?
If floor shift make sure both arms/transfer case shift levers are engaging.

How many positions on shift lever?
And what do they say?I just took out the battery and battery tray there is a vacuum asisted diaphram under it, well while it is running in low drive and low on the transfer case I pulled on the cable with the vacuum hose off and the 4 wheel drive worked like a charm so I shut it off and pushed the diaphram in and held my finger where the hose goes and it held vacuum so I sucked on the hose and it held vacuum so there must be some relay or something that tells it to start vacuum to the diaphram to pull on the cable to the front axle.

I just took out the battery and battery tray there is a vacuum asisted diaphram under it, well while it is running in low drive and low on the transfer case I pulled on the cable with the vacuum hose off and the 4 wheel drive worked like a charm so I shut it off and pushed the diaphram in and held my finger where the hose goes and it held vacuum so I sucked on the hose and it held vacuum so there must be some relay or something that tells it to start vacuum to the diaphram to pull on the cable to the front axle.I just looked up a vacuum actuator switch for $16.00 on the transfer case I think it may be the problem but I wonder if I took it out and made it move freely and put it back in if I can save the bucks.

I just looked up a vacuum actuator switch for $16.00 on the transfer case I think it may be the problem but I wonder if I took it out and made it move freely and put it back in if I can save the bucks.The problem was that the vacuum actuator switch was leaking vacuum where the plastic meets metal obviously if the plastic spins on the switch it is leaking and wont work. My drive train on the shift counsel lit up and everything worked. Advance was $1.00 cheaper than auto zone.:grinyes: