1987 S10 Blazer 2.8 4X4 HUBS won't engage

B&BGaryC · 08-23-2008, 01:11 AM

My 4WD will shift, but the hubs won't engage. When I shift I sometimes get a grinding noise, especially when going from 4 low to 4 high and back...

I noticed there is a vacuum line hanging down and dragging on the ground, but I don't know what it goes to. My friend has a S10 truck with a 2.8 and he says it goes to vacuum pods that I don't seem to have. He gave up on it a long time ago.

Are the vac lines and the grinding the same problem or different problems?
Am I just shifting the 4WD wrong?

Thanks

EYEROCK89 · 08-23-2008, 01:39 AM

My buddy had an 86 Blazer with the same problem. The vacuum line to the 4wd acuator had come off. I'm guessing thats the problem with yours. It;s been 10 years since I helped him fix it so I can;t even begin to tell you where to find the acuator.

Odogg81Malibu · 08-23-2008, 01:51 AM

The acuator or vacum diaphram is under the battery tray

B&BGaryC · 08-23-2008, 04:03 AM

Thanks, when it gets light out I will look under the battery tray. Where does the other end of the vacuum line hook up to?

Is the grinding problem because of the vacuum line or is that just the hub problem?

This forum rocks!

Dr.Fiero · 08-24-2008, 02:20 PM

I could be wrong, but... the '87 2.8 is still up on the inner r/h fender behind the battery box (the later 4.3's were under it).

There should be a vac line going from the engine, down to the transfer case (well, the vac selector switch part of it), then back up to the servo on the inner fender.

The grinding (rarely a good thing!) could be coming from the T-case, or the front diff itself. If you don't have the vac line hooked up, your front gears aren't engaging, so the noise really can't come from there. You COULD drop the front drive shaft, and see if the noise goes away. It's only 4 bolts. Mark the relative position of the shaft to the yokes before you drop it (if you didn't already know).

neo71665 · 08-24-2008, 04:54 PM

correct, on a 87 you should have a vac line that runs to the acuator from the switch on the drivers side top of the transfer case. You should also have a source vac line line running from the TB down the the same switch. Make sure both of those are hooked up correctly.

As for the grinding are you putting the tranny in neutral and giving it a second to stop free spinning or just trying to shift it?

08-23-2008, 01:11 AM	#1
B&BGaryC Registered User Age: 25 Join Date: May 2008 Posts: 6 Location: User is: OffLine	1987 S10 Blazer 2.8 4X4 HUBS won't engage My 4WD will shift, but the hubs won't engage. When I shift I sometimes get a grinding noise, especially when going from 4 low to 4 high and back... I noticed there is a vacuum line hanging down and dragging on the ground, but I don't know what it goes to. My friend has a S10 truck with a 2.8 and he says it goes to vacuum pods that I don't seem to have. He gave up on it a long time ago. Are the vac lines and the grinding the same problem or different problems? Am I just shifting the 4WD wrong? Thanks
	[Reply w/Quote]

08-23-2008, 01:39 AM	#2
EYEROCK89 Mr. Clean Age: 31 Join Date: Nov 2004 Posts: 740 Location: Birmingham, AL User is: OffLine	Re: 1987 S10 Blazer 2.8 4X4 HUBS won't engage My buddy had an 86 Blazer with the same problem. The vacuum line to the 4wd acuator had come off. I'm guessing thats the problem with yours. It;s been 10 years since I helped him fix it so I can;t even begin to tell you where to find the acuator.
	[Reply w/Quote]

08-23-2008, 01:51 AM	#3
Odogg81Malibu Registered User Age: 29 Join Date: Feb 2008 Posts: 51 Location: Fremont,OH User is: OffLine	Re: 1987 S10 Blazer 2.8 4X4 HUBS won't engage The acuator or vacum diaphram is under the battery tray
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08-23-2008, 04:03 AM	#4
B&BGaryC Registered User Age: 25 Join Date: May 2008 Posts: 6 Location: User is: OffLine	Re: 1987 S10 Blazer 2.8 4X4 HUBS won't engage Thanks, when it gets light out I will look under the battery tray. Where does the other end of the vacuum line hook up to? Is the grinding problem because of the vacuum line or is that just the hub problem? This forum rocks!
	[Reply w/Quote]

08-24-2008, 02:20 PM	#5
Dr.Fiero Registered User Age: 42 Join Date: Oct 2003 Posts: 264 Location: Delta, BC User is: OffLine	Re: 1987 S10 Blazer 2.8 4X4 HUBS won't engage I could be wrong, but... the '87 2.8 is still up on the inner r/h fender behind the battery box (the later 4.3's were under it). There should be a vac line going from the engine, down to the transfer case (well, the vac selector switch part of it), then back up to the servo on the inner fender. The grinding (rarely a good thing!) could be coming from the T-case, or the front diff itself. If you don't have the vac line hooked up, your front gears aren't engaging, so the noise really can't come from there. You COULD drop the front drive shaft, and see if the noise goes away. It's only 4 bolts. Mark the relative position of the shaft to the yokes before you drop it (if you didn't already know).
	[Reply w/Quote]


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08-24-2008, 04:54 PM	#6
neo71665 4x4 v6 blazer Age: 28 Join Date: Oct 2004 Posts: 3,415 Location: rison arkansas User is: OffLine	Re: 1987 S10 Blazer 2.8 4X4 HUBS won't engage correct, on a 87 you should have a vac line that runs to the acuator from the switch on the drivers side top of the transfer case. You should also have a source vac line line running from the TB down the the same switch. Make sure both of those are hooked up correctly. As for the grinding are you putting the tranny in neutral and giving it a second to stop free spinning or just trying to shift it?
	[Reply w/Quote]

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