1998 Dodge Caravan van vibrates/shakes while stopping with

Tiny
DJSHYC
  • MEMBER
  • 1998 DODGE CARAVAN
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 153,000 MILES
Recently I heard a grinding noise in the rear coming from my drums. I needed to replace them so I did alon with all the hardware and the shoes and the cylinders. They are adjusted properly and have been bled. Now I get a significant vibration when stopping from high speeds and sometimes but less significantly at medium to lower speeds too. I did the work myself. My mechanic said he doesnt have any ideas as to what would do that.
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Monday, March 23rd, 2009 AT 6:00 PM

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Tiny
CARADIODOC
  • EXPERT
Jack up the wheels and spin them while watching if they wobble. If they do, look at the installation of the drums. If they are not centered on the studs, they won't sit flat against the hub surface.

There is an access hole in the hub to allow access to the mounting bolts. Water can get inside and create a rust spot on the inside of the drum by that access hole. If you don't install the drum the same way, that spot of rust will hold the drum away from the mounting surface making it appear out-of-round. Professional technicians will clean that rust off before machining them. If they were machined with that rust still there, the drums are definitely egg-shaped now.

Did you have the drums machined? Also, if they were rusted tight and you banged them off with a hammer and pry bar, they are likely warped and must be machined.

One thing that a lot of people do to cause problems is not use a torque wrench on the lug nuts. This wasn't important many years ago with heavy rear wheel drive cars, but with lightweight vehicles, proper lug nut torque is critical. Most Chrysler cars and minivans call for 95 foot pounds.

There are four reasons to torque lug nuts. First, over-tightening causes stripped threads that may not show up until the next time someone removes the wheel. Of course, the technician removing the wheel will get the blame. Often the lug nuts have to be cut or chiseled off and the wheel can be damaged.

Tightening the nuts to specs insures a 90 pound person can get them loose to change a flat tire.

Under-tightening lug nuts can lead to the wheel coming loose and wobbling out the friction surface the nuts contact.

Most importantly, lug nuts that are not torqued to the same value lead to warpage of the brake drum or rotor from the uneven stresses during the heat and cool cycles.

If I ever saw a technician installing lug nuts with just an impact wrench and not following up with a torque wrench, I would mention it to his boss, and probably never go back to that shop.

One final note about lug nut studs. Do not use anti-seize compound on the threads. The nuts WILL come loose. Some people insist on using grease. If you do, use very little, then thread the nuts on all the way by hand and torque them. Don't use air tools because the grease will build up on the friction surface from the centrifugal force and allow them to work loose.

Caradiodoc
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Monday, March 23rd, 2009 AT 7:00 PM
Tiny
DJSHYC
  • MEMBER
No I replaced them with new ones
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Monday, March 23rd, 2009 AT 8:01 PM
Tiny
CARADIODOC
  • EXPERT
You could try jacking up the rear axle, then spinning each wheel to see which one is causing the pulsation. If the parking brake cables are not rusted tight, (which means you don't live in Wisconsin), apply it slowly until one drum starts to grab. The wheels might turn easier by hand if you spin them backwards.

It's not unheard of for a new drum to be warped. Some suppliers don't handle them very carefully. Some drums come with instructions telling you to machine them before installing them. Some tell you to not machine them.

If you bought the "cheap" Chinese drums, they often warp after a few thousand miles and must be machined. They're fine after that. One step in the process of making parts out of cast iron is to age them by plopping them outside for 90 days before the final machine work is done. The Chinese don't do that step so the drums and rotors age on your vehicle. Sure it's a hassle to take things apart a second time, but you can't beat the price.

If one of your old drums is still free of scratches, put it back on and see if the pulsation is gone. You should be able to get away without adjusting that one brake out so you don't have to readjust it again later.

Check to see if any one of the shoes does not come all the way back to the large anchor pin on top. If one is held away, the parking brake cable is stuck or adjusted too tight. You should be able to move the parking brake strut rod to compress the anti-rattle spring a little. If it's tight, the parking brake is holding the shoes out a little.

You might also ask to have the drums checked for run-out at the store you bought them from. Most Carquest stores have a brake lathe. It just takes a minute to set it up with a dial indicator to measure if they're warped.

Holler back when you know some more.

Caradiodoc
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Tuesday, March 24th, 2009 AT 4:50 AM

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