1987 Suburban 4WD Problem(s)

About 3 months ago I purchased a 1987 4WD Suburban (with Auto Locking Hubs) that is currently driven once or twice per week for small honey-dos. I finally turned on the 4WD (I know I know) and it has a strange behavior. When I stop and put it in 4H and start to move again (on pavement) the vehicle girates and the front tires feel like they're locking up and releasing once per rotation. It feels like the tires are alternating on the locking and releasing so it is like being in a funky massage chair. On a somewhat related note it is a little big of a bear to put into 4H and I have done the recommened disengage technique as defined in the owner's manual. Sorry for the bad description but this is the best way I can describe it. If you need further explanation than please let me know.

So two questions:

  1. Do the hubs need to be replaced or rebuilt (if they can be rebuilt)
  2. Where would I order the parts from item #1 or whatever parts are needed. It seems that Chevy is phasing out some of the parts for that vehicle.

Thank you in advance for your time.

Reply to
Joe
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From what you wrote above it sounds like the 4WD is operating properly. It IS NOT designed to operated on dry pavement. Doing so can cause damage to your drivetrain. It is only for use on a loose or slippery surface, such as ice, snow, mud, sand, gravel, etc. The proper use of 4WD should be covered in your owners manual.

Reply to
Mike

Thanks for the prompt response Mike, so if I'm understanding you correctly (I'll check my manual) then the 4WD is a little different than I expected. I guess I need to read up on the mechanics, are newer

4WD vehicles different? For some reason I was under the impression you could engage the 4WD on the road.
Reply to
Joe

It will most definitely bind in 4WD high or low on dry pavement in turns. You have a 4WD vehicle, not AWD. The difference is that a 4WD has solidly meshed front and rear axles. Benefit: less slippage, all power can thoeretically make it to the tires. Disadvantage: It is bad for the system to operate it on good traction surfaces, and you have to select it manually.

Someone with more knowledge of that 4X4 system will have to chime in on whether or not shift-on-the-fly is permitted. Your owners manual should detail how and when you should shift into 4WD (and if you can do it at speed, what the speed limit is, etc.)

FWIW, you should not feel any binding in 4WD if you are going perfectly straight with four evenly sized tires. Once you turn, the two axles begin spinning at different speeds, causing binding and wear on all components involved. The tires will be the first to slip, saving the expensive components from severe damage in most cases. Still, don't test the 4WD system operation on dry pavement unless you are going straight.

Toyota MDT in MO

Reply to
Comboverfish

If you are going straight, it shouldn't bind up on pavement. If it is a 'part time' 4x4 system, it will buck like mad on a turn on dry pavement if you are lucky. If you are unlucky, it will explode something like a u-joint or driveshaft or t-case.

When a 4x4 'part time' system is on, the front and rear axles are locked so when you turn, one front (usually) nor rear wheel has to scuff the ground so you are only supposed to use it when the roads are snow covered or dirt.

If your bucking is in a straight line, I would be inspecting the front axle u-joints or CV joints first and then the driveshaft u-joints.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Joe, Sounds like you have been watching the Subaru commercials and the Audi ones where they brag how good their "4WD" drives are, the catch is they are NOT 4WD they are actually All Wheel Drive. The difference is that an AWD vehicle operates using a viscous coupler between the front and rear drive lines. That coupler acts like a clutch that can slip if the load is to high. This allows the front and rear to operate at different speeds when turning. Your vehicle uses a solid gear and chain drive transfer case to shift the front axle in/out of gear. It is either on or off no slippage allowed. That difference sounds minor but it isn't. Without that slippage a standard 4X4 WILL damage the weakest point in the drive line if used on a high traction surface.

Your 4X4 system is VERY stout. However there are a few rules you need to know.

  1. DO NOT operate that vehicle in 4X4 on high traction surfaces such as bare pavement, DRY dirt roads. This causes the drive train to bind up. Something HAS to give to allow it to unbind from this condition. There are NO cheap parts in the system!

  1. Be VERY careful when driving in 4WD. That vehicle will act MUCH differently than it does when only the rear wheels are pushing it.

  2. 4X4 does NOT mean you can drive 60mph in blowing snow or freezing rain and not have a problem. Remember that you still have to STOP. Keep in mind that you are driving a BIG HEAVY vehicle. You CANNOT stop on a dime, in 4X4 this WILL be WORSE.
Reply to
Steve W.

This was the part that worried me, I was driv> If your bucking is in a straight line, I would be inspecting the front

Thanks Mike, I'll look > [snip - nice explanation of AWD vs 4WD]

LOL about too many commercials. Humor aside I appreciate the explanati> 3. 4X4 does NOT mean you can drive 60mph in blowing snow or freezing

The information is appreciated. Having lived in NE for 6 or so years I do understand and appreciate but it never hurts to cover your bases.

A buddy of mine called about an hour ago and is planning on coming out on Saturday to take a look. He's owned 4WD trucks all of his life and gave a few ideas (as I was talking to him realized I should have called him first but maybe someone else can benefit from this thread) but said he would save me the time and pain of messing and would let me know if it is working how it is supposed to.

Enjoy your evening.

Reply to
Joe

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