Front drive shaft replacement part issue

2002 MERCURY MOUNTAINEER
170,000 MILES • 4.0L • 4WD • AUTOMATIC
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LAWRENCE CHENOWETH
  • MEMBER
  • 39 POSTS
When I got the truck the front drive shaft was out so I bought one and put it in and the truck seamed to fight itself. it is all wheel drive so I took it back out and the truck moves fine.
Sep 24, 2019 at 7:40 PM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Good morning,

It sounds like the ratios are not the same for both differentials.

You need to have someone check the actual gear ratio of each differential to be sure they are the same.

When they are different, they will battle each other and give you that sensation.

Roy
Sep 24, 2019 at 10:25 PM
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LAWRENCE CHENOWETH
  • MEMBER
  • 39 POSTS
Is there a way to check myself?
Sep 24, 2019 at 10:26 PM
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LAWRENCE CHENOWETH
  • MEMBER
  • 39 POSTS
As far as I know it is all factory, but if there is a way for me to check.
Sep 24, 2019 at 10:35 PM
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ASEMASTER6371
  • ✓Experienced Mechanic
  • 52,796 POSTS
Look for a tag on each differential. The tag is usually mounted to one of the cover bolts. If there is, give me the number and I will look up the ratios for you.

Otherwise, you need some white-out. Jack up the truck and mark the inside of the tire. Then put a mark on the driveshaft. Turn the tire one complete turn and then count the number of times the driveshaft turns. Give me the number of turns on the driveshaft.

Roy
Sep 24, 2019 at 10:36 PM
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