'got an s-10 4/4,'86 and when i move the lever to 4-w-high or low the light does comes on ,it whines like it's in ..but neither front tire will spin.would someone help walk me through a troubleshoot on this?thanks,Ty

 

Welcome to the site.
10-1 your vacuum modulator isn't getting or holding vacuum. It is located next to the battery ont he fender well. There is a hose that connects on one end, and a cable on the other end. Pull that cable about 1" and put a vise grip on it after you put the t-case in 4x4. Did that fix your problem?

Check to make sure the front driveshaft is locked when you have it in 4x4. Put it in 4x4, then put it in park, reach under the truck and try to turn the front driveshaft. If it didn't spin, your t-case is in 4x4, and the problem lies in teh vacuum modulator, vacuum system, or vacuum hose(s).

Post up what you find out.

 

Hey Hanr3,

I'd like to follow up on this. I have a 90 with the same problem. Driveshaft is unlocked in 2wd and locks in 4wl and 4wh. I pulled the mod off and the vac line has no vacuum so i'm figuring it's the switch, bad hose or whatever. Thing is, when I pull out on the cable it only moves about 1/4". Pulled out and clamped , still no 4wd

Ring any bells?

Thanks,

Rob

 

i have not pulled on the cable to lock in the front end but that is the main idea for the vaccum acuator if there is no vaccum at the acuator i would replace the vaccum switch on the transfer case. also if the vaccum acuator diafram is damaged from a puncter or old age that would cause it to not lock in i found aeasy way of checking is to rase the front just one tire do not put the lever in four wheel drive pull the cable or apply vaccum to the acuator try and turn the tire if it locks then and you have tested the transfercase by puting it in four wheel drive and the drive shaft is locked the problem lies in the vaccum lines, vaccum switch, or vaccum acuator hope this helps it kind of looked like i went in a circle but i think i got my point across.