I have a 2003 Chevrolet Silverado 1500 Z71. When the rear tires brake traction at low speeds it spins then its like one tire locks up for a bit, then when i speed up again its fine. I m wondering if its diff problems. but on the highway its totally smooth and no howling from the diff. at any time.

check out these sites

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Elaine,

not work, do tell what makes you think it dont work (a lamp) or tires slipping or dead tires. (by tires mean that and traction)??????????

what mode fails, of the many, and where.???????



first off, we dont know what your tires are touching.

on road, or off road. pavement or ICE or snow.

that matters big time . (you read manual and match MODE to Road)

your lost operators guide explains all that, right?

eg: how and when to use, 4wd, its all there. I promise.

ControlTrac 4-wheel-drive system



here are the mode. which one , gives you problems.



quote ford with comments.



What are the modes, and how do they differ?

(note this is the operational behavior of a 2008 Ford Expedition. Newer and older Expeditions will vary only slightly)



• 2H 2-wheel-drive with high range gearing (1.00:1) Rear-wheel-drive capability,

2-wheel electronic traction control system is enabled



• 4A 4-wheel-drive Auto with high range gearing (1.00:1) Full-time all-wheel-drive capability, ((best on pavement or any time)

Electronically adjusted torque split to front & rear wheels, Electronically variable center differential,

Front driveshaft & rear primary driveshaft allowed rotational speed difference,

4-wheel electronic traction control system is enabled



• 4H 4-wheel-drive with high range gearing (1.00:1) Part-time 4-wheel-drive capability, (not for dry pavement EVER)

Continuous 50/50 torque split to front & rear wheels, Electronically locked center differential,

Front driveshaft & rear primary driveshaft mechanically locked with no rotational speed difference,

4-wheel electronic traction control system is enabled



• 4L 4-wheel-drive with low range gearing (2.64:1) Part-time 4-wheel-drive capability, (off road usage, mostly)

Continuous 50/50 torque split to front & rear wheels, Electronically locked center differential,

Front driveshaft & rear primary driveshaft mechanically locked with no rotational speed difference,

4-wheel electronic traction control system is enabled, ESC and RSC are disabled



In 4A mode the center differential is electronically-controlled and rear drive wheel bias. The on-board computer monitors for any sign of rear drive wheel slip (loss of traction)

If loss of traction is detected, the center differential is told to send a share of the engine\'s torque to the front drive wheels. It will not let the front driveshaft turn at the same speed as the rear driveshaft.



What about traction management?

1997-2002 model Ford Expeditions offered an optional limited-slip rear differential (LSD). A conventional open rear differential was standard along with the conventional open front differential and the electronic locking center differential.

comment with out LSD, one tire can spin, on say ice.

but the other 3 tires dont, in full time.

linkage may need adjusted, try adjusting, truck is 10 years old, if that doesn't work, might be an internal problem, don't think the worst, one step @ a time

abs systems do not lock on the brakes
they release the brakes when the wheels stop spinning and when the wheels start turning again apply the same brake pressure as before the wheels stopped spinning
check the proportioning valve to the rear brakes to ensure that it is not acting as a one way valve and that is causing the problems
if the compensating port in the master cylinder for the rear wheels is blocked that also will lock the rear brakes

You're going to need to increase the tooth count on the driven gear on the speed sensor. probably with 3 additional teeth in the count.

This is for the front: Removal & Installation

1. Remove 2/3 of the brake fluid from the master cylinder.
   
2. Remove or disconnect the following:
   
   • Wheel
     
   • Caliper. Suspend the caliper from the frame with mechanic's wire. Do not allow the caliper to hang from the brake hose.
     
   • Caliper mounting bracket bolts
     
   • Caliper mounting bracket from the steering knuckle assembly
     
   • Brake pads from the caliper mounting bracket
     
   • Clips from the inside ends of the caliper mounting bracket and discard
     

To install:

1. Install or connect the following:
   
   • Clips to the inside ends of the caliper mounting bracket
     
   • Brake pads to the caliper mounting bracket
     
   • Inner pad (1 wear indicator)
     
   • Outer pad (2 wear indicators)
     
   • Caliper mounting bracket to the steering knuckle assembly
     
2. Perform the following procedure before installing the caliper mounting bracket bolts:
   
   • Remove all traces of the original adhesive patch.
     
   • Clean the threads of the bolt with brake parts cleaner or the equivalent and allow to dry.
     
   • Apply red Loctite®272 to the threads of the bolt.
     
3. Install or connect the following:
   
   • Caliper mounting bracket bolts to the steering knuckle. Tighten the caliper guide pin bolts to 74 ft. lbs. (100 Nm) on 15 series or 80 ft. lbs. (108 Nm) on 25/35 series.
     
   • Caliper
     
   • Tire and wheel assembly
     
4. Refill the master cylinder to the proper level with fresh brake fluid. Pump the brake pedal slowly and firmly in order to seat the brake pads. Burnish the brakes as needed.
   

What is the problem? Too sensitive? What speed does it occur? First apply? Every apply? Wet roads?

Cheap tires, cheap brakes, wrong tire size (not calibrated), contaminated brakes, faulty wheel speed sensor.

Most common problem is cheap rear brake pads.

reomve tire securing the vehicle with tire hanging at it's lowest possition, remove the brake caliper & brake disc , remove nut lock on axle also axle nut , mark and remove strut bolts and push strut out remove ball joint lower bolt and use a fork ( tooling) seperate from hub slide hub off of axle , reverse steps to replace .

Check the fluid in the the axle. Also make sure the brake isn't locking up. You might want to take the axle gear cover off and see if the "C" clip came off or is broken on the gear assembly. Almost sounds like the differentials is locking up.