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post #1 of (permalink) Old 04-02-2000, 04:31 PM
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4x4 Quit working

Hello all, the 4x4 on my 88 (4.3,auto) Blazer decided to quit working yesterday, and I have an idea why but I wanted some advise. I bought this truck about 3 weeks ago, it has 206,000 miles but it runs and looks real good, no 4x4 abuse like I have put it through in the last 3 weeks. Yesterday we were out scouting a public hunting aera and I had been in and out of 4x4 all day. I had driven through some pretty deep water. Then we stopped, got out and walked around for about 1 hour. I got back in put the truck in 4 low, started it and no 4x4, 4 low or 4 high. I have checked everything, vacuum hoses, the diafram, cable to the front diff, the only thing I found wrong is the vacuum switch on the transfer case. I took it out and the pin is sticking. Is there a relay I am missing or would this cause the truck not to go into 4x4? Everything else is fine. Any help would be greatly appreciated.

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post #2 of (permalink) Old 04-02-2000, 06:11 PM
 
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Re: 4x4 Quit working

What I always carry with me is a little plastic t, so that I can connect my vacuum actuator to a source of engine vacuum (while keeping the other thing that needed vacuum working too) if necessary to keep the front differentlal engaged the whole time. Good tip for anyone who has a vacuum actuated front differential.

Another good tip might be to do as much as you can in 2wd, that way, you'll know that if you got in you will be able to get out in the event that something happens to your 4wd...

There is no relay, the vacuum switch thingee is just controlled internally by the transfer case, when you shift it into certain positions. If it's sticking, you might try spraying it with some type of cleaner or degreaser or replacing it. That should solve your problems... [img]/wwwthreads_images/icons/crazy.gif[/img]

Tim
[img]/wwwthreads_images/icons/cool.gif[/img] '79 Suburban 4x4 454, 35x12.5s
[img]/wwwthreads_images/icons/wink.gif[/img] '85 S15 4x4 2.8l, 235/75's
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post #3 of (permalink) Old 04-02-2000, 08:50 PM
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Re: 4x4 Quit working

So, the thing that goes into the transfer case, does it send vacuum back to the diaphragm (which is under the battery, which is a pain)? When the truck is running I have vacuum at the transfer case, there are three vacuum lines that plug into the case, one of the lines has vacuum all the time. So if I understand this correctly, when in 4x2, the vacuum doesn't do anything, when you pull the transfer case lever back the switch allows vacuum to run back up one of thoes other lines and the vacuum pulls against the diaphragm, which pulls the cable out, which lets the diff engage and the light comes on. There is a switch on the diff, on the cable, when I take it out and push in the pin the 4x4 light comes on. When I put the transfer case in 4 high, I can't turn the front drive shaft like it is in 4x4, I guess it is locking at the transfer case end and the diff isn't engaged. Will replacing the vacuum switch on the transfer case fix the problem?

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post #4 of (permalink) Old 04-02-2000, 09:53 PM
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Re: 4x4 Quit working

Sounds like you have how the 4 wheel drive works figured out. Yes I feel it will fix you problem if you replace the vacum switch on the transfer case. They are not that expensive and easy to replace. Sandman had a good idea of you plan to do a lot of 4 wheeling. Also you might want to just get an extra and the tools you would need to replace it while you were 4 wheeling if you should need it. Good luck.

post #5 of (permalink) Old 04-02-2000, 09:57 PM
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Re: 4x4 Quit working

Thank you very much guys. I will let you know if it works. Just for the sake of asking if the diaphragm quit working, or holding vacuum, could you manually pull the cabel out and clamp it with v grips and get out that way?

post #6 of (permalink) Old 04-02-2000, 11:27 PM
 
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Re: 4x4 Quit working

I tried to use the vise grips thing before, and I couldn't get it pulled tight enough so that the vise grips could hold it right... You might want to experiment with yours a bit right now, before the vacuum actuator quits working (I'd be willing to bet that the actuator lasts a long time considering mine is an 85 and the original piece and is still working great... (oops now that I said that, it'll probably break, right? Murphy's law i guess... [img]/wwwthreads_images/icons/tongue.gif[/img])

Tim
[img]/wwwthreads_images/icons/cool.gif[/img] '79 Suburban 4x4 454, 35x12.5s
[img]/wwwthreads_images/icons/wink.gif[/img] '85 S15 4x4 2.8l, 235/75's
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post #7 of (permalink) Old 04-03-2000, 08:49 PM
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Re: 4x4 Quit working

All right, that switch on the transfer case fixed it, dealer item only $26.00. Talking to the guys at the dealer, I guess that switch is prone to fail, they knew exactly what I was talking about. I will now have about 10 feet of vacuum hose and T fittings in the truck at all times. I am really impressed at the off road capabilities of this truck, completely stock, with good tires it goes where I want it to go. No complaints. Thanks for your help.
Rod

post #8 of (permalink) Old 04-03-2000, 11:11 PM
 
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Re: 4x4 Quit working

[img]/wwwthreads_images/icons/cool.gif[/img]

Tim
[img]/wwwthreads_images/icons/cool.gif[/img] '79 Suburban 4x4 454, 35x12.5s
[img]/wwwthreads_images/icons/wink.gif[/img] '85 S15 4x4 2.8l, 235/75's
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post #9 of (permalink) Old 05-14-2000, 01:45 PM
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Re: 4x4 Quit working

I did not replace the switch on my Jimmy. I brought the vacumm lines through the firewall to a three-way valvenear my shifter. To 4-wheel, I pull the Shifter lever into place and open the stopccock. I now can open the stopcock and have a true 2 wheel drive low range. This has come in handy on tight trails when I need to turn sharp.

S-15 Jimmy
post #10 of (permalink) Old 05-17-2000, 11:15 PM
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Re: 4x4 Quit working

I supose that is a cheap way to do it. If you would like something that does the same thing, and don't mind paying for it, you can go to complete manual shift, buy a posi-lok unit. they are around $125, I was thinking of putting one in my S10, and will probably do it to my 94 Z71.



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