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March 2010 Techline

Wrench
Willie Worthy | Writer
Posted March 1, 2010

Techline

Where To Write
Address all correspondence to: Techline Four Wheeler, 831 S. Douglas St., El Segundo, CA 90245. You can also reach us by e-mail at fourwheelereditor@sorc.com; be sure to type the words "Tech Line" in the subject line. All submissions become the property of Four Wheeler, and we reserve the right to edit them for length, accuracy, and clarity. The editorial department also can be reached through the Web site at www.fourwheeler.com. Due to the volume of mail, electronic and otherwise, we cannot respond to every reader, but we do read everything.

Ford Truck Transfer Cases "Pops"
Q.
My brother in law owns a 1990 Ford 3/4- ton regular cab 4x4, with a swapped-in 302 engine and five-speed granny-low tranny. Was the 302 an option in 1990? (His engine is a '95.)

On to the important stuff: When in four-wheel drive and under a load, like going up a steep hill, a popping noise comes from the transfer case area. Everything seems to work fine, but the noise is a little disturbing. Any ideas?
Mike from KS
Via fourwheeler.com

A. The 302 was an optional engine in the F-150 and F-250 that were under a 8,500-GVW rating.

As to the noise, which you describe as coming from the transfer case "area" most likely is a problem with the transfer case itself. This is a chain-drive Borg-Warner 13-56 unit, and my guess is that the chain is worn and has elongated at the spot where the links join. This, for lack of a better word, "stretches" the chain and allows it to jump on the drive sprockets. If it has been going on very long, there also could be damage to the sprockets, and they will be needed to be replaced. These transfer cases also have a bit of wear problem with the oil pump housing, so it might be better to find a replacement, used or rebuilt, other than trying to just change out the chain.

Grand Cherokee Brake-Job Tips
Q.
I helped my cousin redo the rear brakes on his Grand Cherokee. No problem. Then later, when we did the front brakes, and installed new rotors and pads, we used a C-clamp to push the pistons back into the caliper. Everything worked fine, except the front pads seem to be riding on the rotors, and the rotors are extremely hot. Is there some trick to the front brakes?
Eason Liley
Via E-mail

A. The caliper's piston has a special seal that is designed so that when brake pressure is released, it will cause the piston to slightly retract. The normal clearance between pad and rotor is very close to start with, so without proper retraction of the piston, the pad would constantly be in contact with the rotor.

So why is the piston not retracting? There are a couple of things that may have caused the problem. When pushing the piston in with a C-clamp, you most likely put the clamp on only one side of the piston and cocked it in the bore, thus damaging the seal. There is a special tool used to press the piston back in, but you can use a C-clamp as long as you also use a flat piece of metal across the face of the piston so the pressure of the C-clamp is in the middle of the piston. This prevents the piston from cocking in the bore. I always also recommend that the bleeder screw is open when you do this. Otherwise you're forcing dirty fluid back through the line, past the combination valve and into the master cylinder. Doesn't take much contaminant in the fluid to cause a problem.

Generally, I also recommend that you purchase what are called "loaded calipers" whenever doing a brake job on a 4x4 vehicle. This gets you new pads and a rebuilt caliper. The brakes on a 4x4 vehicle are exposed to much harsher elements than a normal vehicle, hence more of a chance for early wear.

You also need to look at the sliding surfaces and make sure that the caliper slides properly as the brake is applied. Roughness or nicks on the sliding surfaces will cause brake drag. These sliding surfaces should also be lubricated with the proper high-temperature grease.

Mystery Thunks On Lifted Ram
Q.
I own a 1999 Dodge Ram 1500. It has a mild suspension lift and a few bolt-on engine modifications. About a week after the warranty expired, I began to notice a rhythmic thunking noise coming from what appears to be the rear axle area. This noise happens when I decelerate or during "easy" braking. It is sometimes more pronounced than other times, but it always seems to happen. What could be causing this, and should I be concerned? How do I fix it?
Jason Burkleo
Weed, CA

A. To me, when you say "rhythmic thunking," it means to me that the noise is continuous and not just a single "thunk." A single thunk could be slack being taken up in a worn U-joint, or even the driveshaft slip yoke binding and then releasing. Well, the U-joint could be really bad, but you would also get the noise when you move away from a stop and normally a bad vibration.

Being rhythmic means that some rotational force is causing the noise. I would think that if it was a problem within the rearend, then the noise would be there all the time. Keep in mind that when you brake or decelerate, the front of the truck drops and the rear slightly rises. Could it be that an e-brake cable, or perhaps part of the exhaust system, is moving and making contact with the driveshaft? That would be the first place that I would start looking.

My next step would be to put the rear axle of the truck on a pair of very secure jackstands so that the tires are off the ground. Block the front wheels both to the front and the back. Have someone sit in the truck and start it up, put it in gear and let the rear wheels turn say, to a point where the speedometer indicates 20 or so mph. Then easily apply the brakes. Now you can carefully listen and try to pinpoint the noise. Even better would be to put it on shop lift where you had better access, being very careful while doing this around rotating parts. Hopefully, you could then pinpoint where the noise was coming from, which would lead you to what was in need of repair.

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