Could my driveline vibration be CV joints?
02-06-2018, 02:28 PM
#16
Did you get a copy of the road force report? If so what were the numbers?
02-06-2018, 06:57 PM
#18
Chronic Tool Dropper
Lifetime Rennlist
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More to consider:
Put the car on stands, preferably with the stands under the suspension at the bottom of the spring/shock absorber on either side. Trans out of gear, parking brake off. Add a dial indicator to the mix, magnet base stuck to something handy and steel. Start at the inside of each side and work towards the wheel. So set up at the cover on the inner CV joint at the trans drive flange. Zero the needle, and slowly rotate the tire and that half-shaft. MOve to the ends of the shaft. Then the outer CV joint. Then the rim in both radial and axial vectors. Move your creeper seat close to the tire, and support a piece of chalk or crayon so it just barely touches the tire, then rotate the tire to make sure it is round on the confirmed-round wheel. Sometimes... Wheels get bent or otherwise distorted from impacts with "things". Tires grow bubbles and bruises from impacts. Something that is apparent from a slow roll is generally going to be outside of the outer CV joint, as the bearing will normally maintain the drive hub and disc alignment. But that's not guaranteed. If you haven't found the cause yet, take the wheels off and test in 2 axes at the rotor hat. Test the drive hub without the disk in place, paying attention to presence of the hold-down screws on the rotors. Make sure the face and center guide ring on the hub are concentric, measuring in two axes where the wheel mounts on each side.
CV joints do wear, and it's hard to detect by feel alone if there's wear. Sometimes swapping the two half-shafts side to side will put any grooves or other wear on the old trailing faces, and the drive faces will be good or at least better. Any damage to the boots? Look for telltale black grease "stripes" on the bottom-side of the tub over each inner CV joint, tell tale of a previous boot failure. The outer is a little more fun to trace as the grease from the joint gets on lots of things before it makes a stripe in the wheel itself. A previous boot failure has a future-failure risk profile related to how long the innards were exposed, how much you drove in that time, and whether the joint was removed and completely cleaned, properly repacked with the correct grease, assembled with new boor qnd cinched up before being driven.
*** The tightening torque on the inner CV joint to transmission drive flange is 62 lbs/ft IIRC. These can be inconvenient to to get tight enough without some care. I usually stack a few extensions on an impact-rated Allen driver. With the parking brake set, I can get good torque on them with the torque wrench from out in the wheelwell area. Doing this well lying on the floor underneath is tough. Much easier IMO sitting in the wheel well area. If the bolts were loose, remove and replace them one by one, cleaning each and checking for straightness along the way.
Put the car on stands, preferably with the stands under the suspension at the bottom of the spring/shock absorber on either side. Trans out of gear, parking brake off. Add a dial indicator to the mix, magnet base stuck to something handy and steel. Start at the inside of each side and work towards the wheel. So set up at the cover on the inner CV joint at the trans drive flange. Zero the needle, and slowly rotate the tire and that half-shaft. MOve to the ends of the shaft. Then the outer CV joint. Then the rim in both radial and axial vectors. Move your creeper seat close to the tire, and support a piece of chalk or crayon so it just barely touches the tire, then rotate the tire to make sure it is round on the confirmed-round wheel. Sometimes... Wheels get bent or otherwise distorted from impacts with "things". Tires grow bubbles and bruises from impacts. Something that is apparent from a slow roll is generally going to be outside of the outer CV joint, as the bearing will normally maintain the drive hub and disc alignment. But that's not guaranteed. If you haven't found the cause yet, take the wheels off and test in 2 axes at the rotor hat. Test the drive hub without the disk in place, paying attention to presence of the hold-down screws on the rotors. Make sure the face and center guide ring on the hub are concentric, measuring in two axes where the wheel mounts on each side.
CV joints do wear, and it's hard to detect by feel alone if there's wear. Sometimes swapping the two half-shafts side to side will put any grooves or other wear on the old trailing faces, and the drive faces will be good or at least better. Any damage to the boots? Look for telltale black grease "stripes" on the bottom-side of the tub over each inner CV joint, tell tale of a previous boot failure. The outer is a little more fun to trace as the grease from the joint gets on lots of things before it makes a stripe in the wheel itself. A previous boot failure has a future-failure risk profile related to how long the innards were exposed, how much you drove in that time, and whether the joint was removed and completely cleaned, properly repacked with the correct grease, assembled with new boor qnd cinched up before being driven.
*** The tightening torque on the inner CV joint to transmission drive flange is 62 lbs/ft IIRC. These can be inconvenient to to get tight enough without some care. I usually stack a few extensions on an impact-rated Allen driver. With the parking brake set, I can get good torque on them with the torque wrench from out in the wheelwell area. Doing this well lying on the floor underneath is tough. Much easier IMO sitting in the wheel well area. If the bolts were loose, remove and replace them one by one, cleaning each and checking for straightness along the way.
02-06-2018, 07:08 PM
#19
Had a car with a similar issue and it was the front wheel bearing was not properly seated or tightened.
02-07-2018, 02:29 PM
#20
Drifting
Thread Starter
I had a 2nd shop re-do the road force balancing. Evidently 3 wheels were way off. I ran it up to 90mph(on a race track, of course) and vibration seems to be gone. I'll be requesting a refund from the 1st shop.
02-07-2018, 02:43 PM
#21
Woo Hoo, glad to hear. I have had the same experience, so now I always ask for the report and do not accept any wheel over 15lbs.