Rear Differential
07-14-2018, 05:58 PM
#1
4th Gear
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Rear Differential
Symptom
'72 vette
driving at about 30 mph......
Noise.... sounded like metal banging......
rear wheels totally locked up......skidded to stop.
Car would only roll back and forth about 2 feet.....then it freed up.....close to home so back in the garage.
thought the e brake may have locked, but inspected and locks ok.....wheels, calipers and rotors are currently off.....
rear end up on blocks......in the air
diff oil recently changed with additive......
how do I go further in the diagnostics??
thx!
'72 vette
driving at about 30 mph......
Noise.... sounded like metal banging......
rear wheels totally locked up......skidded to stop.
Car would only roll back and forth about 2 feet.....then it freed up.....close to home so back in the garage.
thought the e brake may have locked, but inspected and locks ok.....wheels, calipers and rotors are currently off.....
rear end up on blocks......in the air
diff oil recently changed with additive......
how do I go further in the diagnostics??
thx!
07-14-2018, 08:09 PM
#3
Le Mans Master
Member Since: Aug 2017
Location: Cool Northern Michigan
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Slim chance it was the tranny.
With both rear tires off the ground rotate one side and listen. Then rotate one tire one way, the other tire the other way. U-Joint seem ok? You need to eliminate tranny, driveshaft, half-shafts and U-Joints as suspects.
Don't run it when up on jackstands. The half-shafts will be at a bad angle and could cause damage.
Very strange that you just changed the axle fluid. Even stranger that you could still roll it 2 ft. Might be the Posi. Will have to remove the leaf spring, rear exhaust and rear cover for inspection.
With both rear tires off the ground rotate one side and listen. Then rotate one tire one way, the other tire the other way. U-Joint seem ok? You need to eliminate tranny, driveshaft, half-shafts and U-Joints as suspects.
Don't run it when up on jackstands. The half-shafts will be at a bad angle and could cause damage.
Very strange that you just changed the axle fluid. Even stranger that you could still roll it 2 ft. Might be the Posi. Will have to remove the leaf spring, rear exhaust and rear cover for inspection.
Last edited by HeadsU.P.; 07-14-2018 at 08:11 PM.
07-14-2018, 10:28 PM
#4
Tech Contributor
Sounds like one or more of the ring gear bolts backed, got stuck, and sheared off inside the diff. Not an uncommon problem. Sometimes the damage isn't too bad, other times it destroys the posi case. If there is no other obvious external issues, I advise removing the diff and pulling the cover for a look. It was more common when GM went with the flanged head bolts, no lockwasher or Loctite used. Those would be in late 77-79.
07-15-2018, 11:43 AM
#6
4th Gear
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Slim chance it was the tranny.
With both rear tires off the ground rotate one side and listen. Then rotate one tire one way, the other tire the other way. U-Joint seem ok? You need to eliminate tranny, driveshaft, half-shafts and U-Joints as suspects.
Don't run it when up on jackstands. The half-shafts will be at a bad angle and could cause damage.
Very strange that you just changed the axle fluid. Even stranger that you could still roll it 2 ft. Might be the Posi. Will have to remove the leaf spring, rear exhaust and rear cover for inspection.
With both rear tires off the ground rotate one side and listen. Then rotate one tire one way, the other tire the other way. U-Joint seem ok? You need to eliminate tranny, driveshaft, half-shafts and U-Joints as suspects.
Don't run it when up on jackstands. The half-shafts will be at a bad angle and could cause damage.
Very strange that you just changed the axle fluid. Even stranger that you could still roll it 2 ft. Might be the Posi. Will have to remove the leaf spring, rear exhaust and rear cover for inspection.
07-15-2018, 11:46 AM
#7
4th Gear
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Sounds like one or more of the ring gear bolts backed, got stuck, and sheared off inside the diff. Not an uncommon problem. Sometimes the damage isn't too bad, other times it destroys the posi case. If there is no other obvious external issues, I advise removing the diff and pulling the cover for a look. It was more common when GM went with the flanged head bolts, no lockwasher or Loctite used. Those would be in late 77-79.
07-15-2018, 01:29 PM
#8
Race Director
Sounds like one or more of the ring gear bolts backed, got stuck, and sheared off inside the diff. Not an uncommon problem. Sometimes the damage isn't too bad, other times it destroys the posi case. If there is no other obvious external issues, I advise removing the diff and pulling the cover for a look. It was more common when GM went with the flanged head bolts, no lockwasher or Loctite used. Those would be in late 77-79.
