Half-shaft timing, fact or voodoo???
Thread Starter
Heel & Toe
Joined: Sep 2007
Posts: 22
Likes: 0
From: Kenesaw NE
Half-shaft timing, fact or voodoo???
When I put new U-joints in my half-shafts, the manual says to be sure that the trunnion carrier is 90 degrees away from the trunion carrier on the other side. Since we are working on one side of a differential this was very hard on my head, it seems like "only add air to your tires when the valve stem is in the "up" position", because as soon as you drive it and turn a little everything moves independently side-for-side anyway. Well, I called the outfit I had been buying parts from and asked them, they said they had never heard of anything like that before and agreed that it doesn't make any sense, but they checked the manuals they had and guess what, they said the same thing! So I did put it together that way but with all the yanking and positioning required to get them back in I could not gaurentee that it was really precise. Is there something about a Corvette differential that I just plain don't understand? I have not lost a great deal of sleep over it, but I would like to understand what the deal is, so any comments appreciated! Thanks, Bill
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Not voodoo. Phasing of shafts with U-joints may or may not be important...depending on the shaft design and its application. If the service manual says to phase it a certain way, you can bet there is a need to do it. [GM would rather call out such a need in a manual than re-design the system to be more robust.]
Drifting
Joined: Oct 2007
Posts: 1,317
Likes: 22
From: Marina CA
It's a fact,any u-joints in a rotating shaft assembly that are not clocked or in phase will give you a vibration thay you'll definitely feel. Plus that vibration you feel is also raising havoc with all of the components it's associated with.
Thread Starter
Heel & Toe
Joined: Sep 2007
Posts: 22
Likes: 0
From: Kenesaw NE
Yeah, I understand about two joints on one shaft needing to be clocked properly, like a driveshaft with a splined slip-joint, but here we are talking timing one shaft with another shaft on opposite sides of a differential unit, as soon as the car moves around a little they will have no relation to each other.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Yeah, I understand about two joints on one shaft needing to be clocked properly, like a driveshaft with a splined slip-joint, but here we are talking timing one shaft with another shaft on opposite sides of a differential unit, as soon as the car moves around a little they will have no relation to each other.
Yes you are right on this. They are constantly changing position so to clock them in is a joke.
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Years ago...1972...I had a bud that would actually jack up his 70 GTX and "synchronize" the position of ALL 4 tires in relation to where the white letters were "located". 
He would try this on Sunday afternoons after a good wash and wax. It made him nuts that they wouldn't stay in sync. He would swear that those tires were "defective". 
I tried to tell him that in a turn, one side went faster than the other and even then ... every time he barked 2nd gear, the rears would slip over 2 or 3 spins. He said I was NUTS and that was just stupid. 
I wonder what ever happened to that ole boy!
Maybe he got a job designing posi rear ends for GM!
This thread made me think of him after all this time.
He would try this on Sunday afternoons after a good wash and wax. It made him nuts that they wouldn't stay in sync. He would swear that those tires were "defective". I tried to tell him that in a turn, one side went faster than the other and even then ... every time he barked 2nd gear, the rears would slip over 2 or 3 spins. He said I was NUTS and that was just stupid. I wonder what ever happened to that ole boy!
Maybe he got a job designing posi rear ends for GM!
This thread made me think of him after all this time.
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