99 chevy s-10 blazer 4x4 wont work?

does the front dif lock in?. also check the vacumm switch

on top of the t-case for sticking

The front diff on that truck will always be engaged the differnce from 4hi to 4lo is that both front wheels engage in 4lo as to it being limited slip on the front in 4hi it sounds like the hubs are not locking in just like on the old trucks with manual locking hubs if you dont lock them in by hand the front wheels wont pull well on the new trucks when you hit the 4 wheel drive button it automatically locks the hubs and ingages the transfer case the front diff. is mechanical as long as the drive shaft is hooked up the front diff. will turn. heres a way to check it yourself jack the truck up off the ground front and back put it in 4 lo and see if the front driveshaft is turning and see if the front axels are turning...then go from there put the transfercase in 2hi the front driveshaft shouldnot turn if so you should be able to stop it by hand in 4lo you will not be able to stop the driveshaft by hand..BE CAREFUL NOT TO LOSE ANY FINGERS

Chances are it is either the transfer case shift motor, or the switch. You can check the connector at the motor to see if it is getting power with a voltmeter, or a test light. If it is not the problem is in the switch, or the wiring. If there is power at the connector, have someone flip the switch while you are under the truck to see if the shift motor is working. You should be able to hear it, or see it move the linkage. Both parts aver available through the dealership, and the shift motor is available aftermarket. And just in response to the answer above, my F-250 has had alot of problems witht he 4wd system, which is undeniably common, and Dodge trucks are very commonly having similar problems. I've replaced as many front axle disconnect actuators on Dodges as chevys, and more trnasfer case motors on Fords than anything.

make sure the front diff is engaging, there is a vacume diaphram under the battery holder. make sure when u put it in 4x4 that is working it should pull a cable that engages the front. if that isnt workin then something is wrong, with the switch on the t-case and it needs to be replaced. that or a vacume came loose be hind the distributor there is a hose that gose to the seitch then to the diphram check that. but make sure the t-case is engauged by puting it in four and with the car off try turning the front driveshaft if it dont turn its workin. good luck

Blazer 4x4

More often than not there is a vacuum leak from the back of the upper intake and the diaphram actuator under the battery tray. Often someone has replaced the battery due to a battery leaking acid all over the tray. Well when this happens it takes out the vacuum lines under or by the battery tray.

I removed the battery tray and with the engine, and power off, I unhooked the vac line from 4x4 actuator and took a deep breath, and blew ... I heard bubblilg noises. somehow the vac line has water in it??? Need to replace 17 year old lines for $4.00.

check the wire from the top of the of the front differential to the plug on the inside of the frame on drivers side

check the gear cord it runs through your gear shift and if its not that I'll be your trani. my sisters is doing the same thing

http://www.blazerforum.com/archive/threads/4x4-won...

check here, there are a few tips. if it isn't anything on there, then i am at a loss...

good luck!