CRG Discussion Forum

Camaro Research Group Discussion => General Discussion => Topic started by: Damon on October 24, 2010, 06:49:14 PM

Title: Clutch fAan vibration
Post by: Damon on October 24, 2010, 06:49:14 PM

I have a 69 Camaro RS factory AC car with a 7 blade 18" fan.  I restored the car then removed the numbers matching engine and currently have a 383 with the previously mention fan and clutch fan.  Since teh 3783 was in I purchased a new clutch fan but used my existing 7 balde fan.  The clutch fan wore out fast creating a vibration in specific RPM ranges.  I replaced the clutch fan with a new one using the same blade.  Now the new one has worn out and started to vibrate again.I removed the clutch fan and blade and vibration is gone.  My question is could my original 1969 7 blade 18" fan be out of balance causing the clutch fans to fail or have I had a string of bad luck with the 2 new clutch fans?  The clutch fan part # is 27071397 and I believe it came from Car Quest.

If replacement is necessary for both what would you run for a blade and clutch fan? Is there a better brand?

Title: Re: Clutch fAan vibration
Post by: JohnZ on October 24, 2010, 08:56:43 PM
It's extremely unlikely for an undamaged original fan to cause a vibration; what's more likely is that it's the fan clutch, especially if the hole in the attaching flange on the clutch isn't properly mated to the pilot on the water pump hub. Most GM water pumps through 1970 had a 5/8" pilot protruding through the water pump pulley, and the correct fan clutches had a 5/8" hole in the flange. Many pumps changed to a 3/4" pilot in 1971, and the mating fan clutches had a 3/4" mating hole in the flange.

If you install a fan clutch with a 3/4" hole on a water pump with a 5/8" pilot, it won't be precisely centered, and the resulting vibration can fail the clutch and take out the water pump too; most clutches with a 3/4" pilot hole in the flange include a precision 3/4"-to-5/8" adapter bushing to center the clutch on the water pump pilot, and if you don't use it, you'll have vibration and major failure.

Most aftermarket auto parts store fan clutches aren't thermostatically controlled, and are junk; most of the Camaro parts houses have the current GM replacement Eaton fan clutch - that's the one you want.