89 S-10 Blazer 4wd doesn't engage

Hey, I don't know how much coincidence it is with the Friday the 13th thing. But yesterday was the first time in ages I managed to get my S-10 Blazer stuck up to the axles in mud. Had to call for help to get
pulled out. For whatever reason, the four wheel drive isn't engaging. (OOOH, this is gonna be expensive!)
I tried four wheel high, and four low. Spun the rear wheels in the mud, but the front drive didn't engage. Woulda been nice if it had, I'd likely been able to drive myself out.
The truck is a 1989 model. 4.3 engine, 265 K miles.
I mentioned this to a friend of mine I visited on the way home. He reached under the battery tray, and had me pull the four wheel drive. And the plunger on the vac actuator did its thing. I think the vac actuator pulls a cable.
Three or four years ago, the front gearbox was a mess, and I had to have it replaced with a used one. And then a year or so after that, the front drive was partial engaged, and making awful noise. The repair shop had to replace the cable (had a used one, off the replacement gearbox I'd had put in). and they had to dealer order a spring and clip to put on the end of the cable.
Anyone out there have experience? Is there some common part that breaks or some aftrmarket cable to activate the 4WD?
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Christopher A. Young
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Chris:
I had an '87 but it was sooooo long ago that I don't remember a lot about it. Certainly don't remember this problem. Seems to me there was a vacuum switch on the transfer case that was occasionally troublesome, but I don't recall if this was the symptom. Why not just check with the dealer on the cable if you suspect it? The cable can't be that much. Frankly, I don't recall a cable that was used for the front wheels. I guess I'd have to ask if you're certain that it's really a cable.
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-Mike-
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I have had to replace that switch on the wheel. It has two wires going to it and a ball bearing looking thing on it. It was not that it wouldn't go into 4WD it just make a loud clicking noise when driving.

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Hmm. Not sure what that is. But, I'll have a look. I take the truck in for safety inspect on Tuesday, and will ask them to see if they can find the problem. I had the same garage work on the 4wd when it was making awful noise, so maybe I need to ashcan the factory engage system.
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From what I know, there is a vacuum line from the handle on the floor. That goes to an actuator (diaphragm) under the battery tray. The vac diaphragm pulls on a cable which goes to the pumpkin.
sounds a bit complicated, eh?
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News flash. Took the truck to a shop. The actuator is fine, but something is dead in the front gear box. The shop guy mentioned the pin that goes into the ring gear.
Question: I did not get the owners manual with the truck. This is my first 4wd. I was told to engage the 4wd every couple weeks to keep the fluids circulated, adn the cable freed up. So, every couple weeks I'd be going down a straight stretch of road, and reach down and pull the shift into four high. Let that go for a couple hundred yards and t hen shift back to two high.
If I'd been exercising the fluids and all, what could have gone wrong with the gearbox?
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Who ever told you that was feeding you a line Chris. Your front end failed just like all mechanical things fail. They just do. Fix it, and drive on. Glad you at least found out what was wrong - nothing is worse than having a problem that does not diagnose easily.
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-Mike-
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It's very possible that most or many users only use the 4wd once a year when they go to the hunting cabin, and it works fine, then. I'm really wondering if my exercising the thing (while going down the road at 25 to 30 MPH) is what killed the gearbox.
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Not at all likely Chris. It's not good to put any truck into 4WD on dry roads, but it isn't going to hurt the differential to do so in the manner you described. Your truck will handle being put into 4WD at speeds much greater than 25-30mph. It's the prinicple of exercising the fluids that I say is hogwash. Whoever told you that was just plain full of crap. What you want to be careful of is not slamming the thing into 4WD. Take you foot off the gas and let the truck come into 4WD before you get back into it. You can keep a steady speed and do it, but you'll make life a little easier on the thing if you simply take your foot off the gas and let the front end come in.
Let me get this straight though... the garage told you that the front differential was bad? Or did they tell you that the transfer case was bad? Both are repairable, but the transfer case is a lot easier beast to deal with.
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-Mike-
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Not at all likely Chris. It's not good to put any truck into 4WD on dry roads, but it isn't going to hurt the differential to do so in the manner you described. Your truck will handle being put into 4WD at speeds much greater than 25-30mph. CY: Does different size tires, front and back, have an effect?
It's the prinicple of exercising the fluids that I say is hogwash. Whoever told you that was just plain full of crap. CY: Very possible. I have no way to know.
What you want to be careful of is not slamming the thing into 4WD. Take you foot off the gas and let the truck come into 4WD before you get back into it. CY: Oh, coasting in neutral,w oudl that be good?
You can keep a steady speed and do it, but you'll make life a little easier on the thing if you simply take your foot off the gas and let the front end come in. CY: Thanks.
Let me get this straight though... the garage told you that the front differential was bad? Or did they tell you that the transfer case was bad? Both are repairable, but the transfer case is a lot easier beast to deal with. CY: I can't remember off hand. He said something about a pin that engages a ring gear, and that was likely what was shot.
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http://www.gegeonline.it/startrek/serie/p-mccoy.jpg
Jim! He's dead!
(Truck didn't pass the state safety inspection this AM, so I'm looking for another truck. Any advice on how to find another truck?)
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Yup - go to places that sell trucks with lots of money in your pocket and a good credit rating. Give them all your money, sign the next 5 or 6 years of your life away and drive out in the vehicle of your fantasies. You can shave a couple of years off of the sign your life away part by buying used.
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-Mike-
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By gosh, I think he's got it! Five years of payments, and plus repairs and gas and oil and.... oh, and a couple firstborn sons and....
More seriously, I'm thinkign private sale, used bucket of bolts to get me around for the next couple years. Worked the last time, I got 140,000 miles out of the bucket of bolts. Doesn't owe me anything.
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Hey Chris - I found my manual out in the garage. Man - it's been years since I pulled that one out of the stack. Let me know if you want me to scan the pages for R&R that cable. BTW - you're obviously right about the cable. I know I've removed it before because I would have had to in order to do some of the work I did on my truck, but I sure don't remember it. Anyway - email me after fixing the munged address in my sig if you want the scanned pages.
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Dear Mike, Thanks for the offer of scanned pages. The garage find out that the cable was OK. What's defective aparently is the operator. I didn't get an owners manual with the truck. Do you have owners manual pages of how to operate the drive as Chevy instructs?
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www.4x4posi-lok.com Model #500 This is an aftermarket cable to engage the front axle.

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Thank you, Bob. I did take a look at th e web page. Looks like good stuff. There is a place about two hours from me that sells the kit and does installs. I emailed them, and will phone on Monday, Tues if they are closed for MLK day. One of the th ings I've been liking about the truck is having the 4wd on tap for snow storms, etc. And it doesn't do much good when the 4wd fails when I need it the most. Again, thank you. I'm pursuing the link.
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Your 4WD problem could very likely be coming from inside your transfer case. If the mode fork gets stuck when it shifts you will have only 2WD or neutral than function properly. This could be cause by wear inside the case itself or just wear of the mode fork and slider.
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Doesn't that only apply to 4 Low problems?
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Thanks for the good idea. The shop said that it wasn't practical to rebuild the front gear box, and that it would be about $500 to get a used one and install it.
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