OT...How to check four wheel drive?

Hey guys the wife wants a Blazer. I have found one I'm going to look at, But how can I tell if there may be potntial problems with the transfer case?

Any other problems I should look for?




86TT225, 99WR, WR timing, throttle stop trimmed, air box lid removed, White Bros head pipe, silencer and air filter. De-octopussed. Works frame guards and Thumper Rad Guards, Scotts steering damper. Odometer and headlight removed. Moose hand and mud guards. YZ stock tank, IMS seat and number plate. Renthal Jimmy Button "highs" and Renthal Soft half waffle grips. AMA, SETRA, Happy Ramblers MXC.

One way to check just to make sure it works is to put it in 4wd on pavement and turn in a sharp circle. It should buckle and jerk which means that it works cause the gears are binding up since the tires can't slip. Don't do this on a regular basis though cause it's not to good for any of the drivetrain components. You could also put in in 4wd and peel out on a dirt road and have someone watch to make sure the front tires are spinning.



When in doubt, GAS IT!

Bring it to a garage or transmission shop and have it inspected. It may work know but could potentially be on the way out. Testing it on pavement will tell you it works but won't tell you the condition of it.

Good luck

I’ll assume you’re talking about a late model Blazer as opposed to the older pickup-sized ones…

I don’t know too much about the light-duty 4wd system, but the last one I saw had a chain-drive New Process transfer case in it and an axle engagement system similar to my full-size pickup (or a Tahoe).

At any rate, to check the transfer case during a test drive find some dirt, stop the car, and put it in 4wd. Roll forward about 20 feet, then backwards another 20 to give the axle a chance to engage (the 4wd light should come on). Then turn the wheels hard and make a circle. The truck should fight the turn, trying to push out of it. If it turns normally then the 4wd is not engaging.

This does not apply to all-wheel drive systems. Most Grand Cherokees I’ve seen were all-wheel drive despite saying “4x4” in about fifty different places (false advertising IMO), and can be driven on the pavement with the so-called “4wd” engaged and will not “push” when turned. I don’t think the Blazer has an all-wheel drive option but I could be wrong. If the owner or salesman is not sure check the manual.

Despite the bad rap modern 4wd systems often get I’ve never heard of a TC failure. Most problems seem to involve the axle engagement. A switch in the transfer case turns on a solenoid or servo which locks the axle. When the axle engages another switch activates the 4wd indicator light either on the dash or on the floor by the lever. The push-button systems I’ve seen use a solenoid to shift the transfer case.

In short all the problems I’ve seen with modern GM 4wd systems were of the hundred-dollar variety or cheaper, like a fifty-cent fuse.

I agree with Mike that having a mech. check it out is a good idea, but, like anything else, it could be a waste of time and money unless you have one you trust.

There is no way I know of to foresee future problems w/out a crystal ball, but if you have a mech look at it I’d ask him some specific questions:

Check U-Joints for grease and play. Because 4wd rarely gets used in most SUVs, front U-Joints tend to rust more quickly, bind up and become loose.

Oil level and type in TC. Most use ATF. Checking the internals is out of the question unless you have a few grand and a weeks time. This should go w/out saying but he should check the seals while he’s at it.

Oil level in front diff. See above about the seals, lack of use can also lead to premature seal failure, especially if it is worked hard later.

Front CV and axleshafts. I should have mentioned these earlier as the likeliest thing to fail and cost you big $$$. Have him check the dust covers and look for axial play. Have they been serviced? Most shops cannot duplicate the factory dust cover retainer exactly so he should be able to tell if they’ve been taken apart. If they have I’d get nervous.

You may get under there yourself to make sure there are skid plates for the TC and front diff. You can generally tell how hard the vehicle has been driven off road by the condition of these skid plates (just like your WR :) )

Hope this helps.

Several of my friends have S-10 Blazers,all of which have seen at least a little off-road use.A couple of them have been really badly abused. With good tires it's quite impressive where these little trucks will go.They all seem to be quite reliable, despite the severe use.No engine,tranny or transfer case troubles to speak of. The most expensive repair that I am aware of was the replacement of both front drive axles.Both outer CV joints were worn out because the owner had been using the truck for several months in 4WD low on concrete to drag large storage buildings around.The only common driveline complaint that I can think of is the hubs not locking when 4WD is engaged.The hubs are locked by intake vacuum and occasionally a hose will fall off or the vac. control will malfunction,but for what it's worth, as far as I know they are good vehicles.

If it does not go into 4WD, check the silver colored vacuum solenoid on the transfer case. It's located on the driver's side, and has a three-way vacuum hose adapter connected to it. If you pull off the hoses and they are saturated with Transmission fluid, the vaccum switch it bad. It's a dealer item for about $35. Good luck.

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