Drive vibration
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,030
Likes: 4,174
From: US-PNW
What operating issue are you trying to solve?
With the engine off, can you feel any wobble with your hand? When you spin the fan by hand does it feel smooth with just a smidgen of drag?
The fan clutch is operated by a thermal spring and internal fluid. Kinda like an auto trans converter with fluid coupling; as the spring warms up it "locks up" and activates the internal fluid coupling. When cold you should be able to hold the fan still with the engine idling -- I don't think I'd do this by hand though. If you apply a heat gun to the front of the clutch, it should "lock up" and be difficult to turn and will want to pull on the fan belt too.
With the engine off, can you feel any wobble with your hand? When you spin the fan by hand does it feel smooth with just a smidgen of drag?
The fan clutch is operated by a thermal spring and internal fluid. Kinda like an auto trans converter with fluid coupling; as the spring warms up it "locks up" and activates the internal fluid coupling. When cold you should be able to hold the fan still with the engine idling -- I don't think I'd do this by hand though. If you apply a heat gun to the front of the clutch, it should "lock up" and be difficult to turn and will want to pull on the fan belt too.
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 2,364
Likes: 103
From: Centerville Louisiana
What operating issue are you trying to solve?
With the engine off, can you feel any wobble with your hand? When you spin the fan by hand does it feel smooth with just a smidgen of drag?
The fan clutch is operated by a thermal spring and internal fluid. Kinda like an auto trans converter with fluid coupling; as the spring warms up it "locks up" and activates the internal fluid coupling. When cold you should be able to hold the fan still with the engine idling -- I don't think I'd do this by hand though. If you apply a heat gun to the front of the clutch, it should "lock up" and be difficult to turn and will want to pull on the fan belt too.
With the engine off, can you feel any wobble with your hand? When you spin the fan by hand does it feel smooth with just a smidgen of drag?
The fan clutch is operated by a thermal spring and internal fluid. Kinda like an auto trans converter with fluid coupling; as the spring warms up it "locks up" and activates the internal fluid coupling. When cold you should be able to hold the fan still with the engine idling -- I don't think I'd do this by hand though. If you apply a heat gun to the front of the clutch, it should "lock up" and be difficult to turn and will want to pull on the fan belt too.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,030
Likes: 4,174
From: US-PNW
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 2,364
Likes: 103
From: Centerville Louisiana
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Does the vibration occur while in neutral and bringing the RPM up, or only when in a gear and moving down the road? Auto or manual trans?
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Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
your Z alignment for your drive shaft is off
your running a junk centerforce clutch
your u-joints are bad, installed wrong, or loose
your rear end snubber bolt is loose.
output shaft bearing bad
your running a junk centerforce clutch
your u-joints are bad, installed wrong, or loose
your rear end snubber bolt is loose.
output shaft bearing bad
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 2,364
Likes: 103
From: Centerville Louisiana
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 2,364
Likes: 103
From: Centerville Louisiana
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
Ok, so not flywheel balance or clutch components since there are none. since it's only when it's moving that eliminates the fan all together.
when it's going down the road put it into neutral while its still going at a good clip and the vibration is present. If the vibration stops, or changes dramatically as engine RPM comes down, then look to the transmission or torque converter balance, that doesn't seem likely though.
If the vibration continues then start looking at wheel balance or balance issues with the rest of the drive train, drive shaft, half shafts, ujoints, shaft alignment issues, etc.
when it's going down the road put it into neutral while its still going at a good clip and the vibration is present. If the vibration stops, or changes dramatically as engine RPM comes down, then look to the transmission or torque converter balance, that doesn't seem likely though.
If the vibration continues then start looking at wheel balance or balance issues with the rest of the drive train, drive shaft, half shafts, ujoints, shaft alignment issues, etc.
Last edited by REELAV8R; Mar 10, 2022 at 05:58 PM.
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,334
From: North of Toronto - Ontario
If you want to eliminate the clutch fan (seems unlikely) you can temporarily tie it so it doesn't spin, it's not a mechanical fixed connection so it's free to not turn until the motor reaches a certain temp. Can't go too far or too fast but might be enough to know it's fine
M
M
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
your output shaft bearing bad.
question, at what speed does the vibration start showing? around 70mph??
