Rear drum brakes only engage in 4x4

[zekew64]

I actually think that it could be an electronic issue -- TMK, if he's not getting braking power unless he's in 4WD, it could be the ABS/VSS sensors aren't sending wheel speed info while the system is only in 2wd. COuld be a faulty wire or a bad ground, or even the sensors themselves could be bad.

However, check this only if the hydraulics check out. I've heard about speed sensors failing after about 10 years or so on the road, sooner if you live in an area where you deal with snow on a regular basis, due to corrosion.

 

[black_demon69]

Wheel cylinders could be stuck.

 

[RangerSVT]

... I'll pull the drums apart tomorrow and adjust them.

Great idea

SVT

 

[ab_slack]

I actually think that it could be an electronic issue

Well you even said in previous posts that they work when the ignition is off when the rear is lifted.

So two conclusions I draw from that. The hydraulic part of the system is functioning cause when you have ignition off it reverts to a dumb system. So you know the brake shoes are getting pushed against the drum. So if there is anything mechanical in the drum it is probably only the adjustment...if anything at all.

And then you said that when ignition is on they keep spinning.

So something is occurring when you have the truck running cause that is when they don't seem to work. With engine running you have the power assist. I doubt that is going to make it not work. That means it is the ABS system which makes sense because the ABS system works by overriding the hydraulic part of the system when it tries to prevent wheel lockup. So your conclusion that it is something electronic makes sense BUT...

BUT does that mean there is something wrong?

The ABS system works by looking at the speed of all the wheels making conclusions about wheels locking up and interrupting the braking force to the respective wheel (or wheel pair) to prevent lockup. I personally have no clue how it is going to react when you do something like jack the rear end up expect it will probably is going to confuse the system.

Which leads me to look at this comment:

If you have the rear wheels off the ground, in gear and turning. The front wheels are not turning. The computer thinks you are in a panic stop and is preventing the rear brakes from locking and causing a spin.

I have to wonder if it is the electronic wizardry that is just messing with you and if there is any real problem to begin with.

You know the hydraulic part of the system works, and adjustment may even be okay. At most the adjustment is off in, but it should be possible to adjust without taking the rotor off.

 

[holyford86]

I'd try adjusting the brakes properly before throwing money at it, all you have to do is jack up the back and safely support it, put it n neutral and pull the rubber plug off the backing plate and using a wide flat bladed screwdriver, turn the adjuster until you feel a slight drag when spinning the wheel by hand. If that doesn't make a difference pull the drums and make sure the wheel cylinders aren't stuck, you might get lucky and find a stuck cylinder.

Sent from my XT897 using Tapatalk

 

[BeeTeeBee]

Thanks for all the help.

I adjusted the rear brakes and it seemed to do the trick. I guess I thought the problem was more complex than that.

 

[bmerr98]

Thanks for all the help.

I adjusted the rear brakes and it seemed to do the trick. I guess I thought the problem was more complex than that.

You wouldn't be the first around here to make a mountain out of a mole hill!

Glad you got it worked out.