Topic: Unusual Wear on Half Shaft
in Forum: C3 Driveline Components
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My car is a 1975 Corvette with over 100,000 miles. I'm in the process of replacing the Passenger side U joints on my half shafts as I heard a noise and noticed that one U joint retaining clip was missing and the cup was working it's way out of the half shaft.
(modified large images to links)Adams' Apple 2008-07-13 18:47:47
I noticed unusual war on the yoke of the inboard side of the half shaft (see photo 'Wear on Pass side Half shaft at Diff 2'. The half shaft is interferring with the differential yoke.
Pic 1
Pic 2
Pic 1
Looking from the rear at the differential and half shafts, I noticed that the driver side differential carrier yoke has a large gap to the differential vs the passenger side ( and this is the passenger side with the unusual wear).
Pic 2
One other thing that I notice is that the the differential trunion seats are not exactly 90 degrees to each other ( see photo Center view of Diff and Half Shafts (Medium))
Pic 3
Pic 3
Can anyone help me determine what is causing the unusal wear on the passenger side?
Also why is there a larger gap on the driver side of the differential?
(modified large images to links)
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Oh boy, you got some more work to do.
kstyer 2008-07-13 18:39:15
First, keep in mind the drive shafts are also the support for keeping the rear tires upright. It used the links below the shafts and the shafts to maintain suspension position.
This means there is a lot of stress not only rotational, but in and out stress on the u-joints and shafts as well. The trunions, I call them yokes, have hardened ends inside the diff. These rest on a shaft in the center of the diff called the pinion shaft, not to be confused with the pinion gear.
As the end of the yoke shafts wear, the tops of the tires start to tilt inward when the weight is on the tires.
The wear you see is due to the joint allowing the shaft to hit the yoke due to the joint failing, and allowing play. That is the wear you see. That is cured by replacing the u-joints.
Game still on. The reason you see the gap on both sides of the diff is the fact the shaft ends are worn inside the diff. If you pull on them they will move out a bit. The cure is to replace the yoke/shafts. At least one of them has been replaced by a rookie. That is why they do not line up evenly. The really should line up. The way they are can create driveline vibration and result in more problems and wear. This may have an influence on the problem you have now. You can also get vibration throught the car under certain loads and shaft rpm.
So as you do the joints, it's a bandaid. You need to take the shafts out of the diff, and you will need at least one, if not both, along with the clips that hold them inplace. Replace the side seals in the diff housing at the same time. That also means a gasket and new fluid. Make sure it has the posi additive when refilled.
Yes it get worse. You need to take the spring out to take the diff out, to take it apart and get inside to do the work.
Not what you wanted to hear, but you should do it right to prevent more problems and grief in the near future.
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Ken is right on with all of the info...the u-joints are junk, and need replacing, as do the stub axles/yokes.
My opinion is the diff should be pulled and repaired/rebuilt, with new stub axles/yokes, as Ken says.
One thing I will add, tho...the yokes will rarely line up in use, unless the posi unit is locked/welded. The two half-shafts do spin at different speeds when turning corners, so even if the yokes start out perfectly aligned, they will not still be aligned after a trip around the block.
On a happier note tho...you do have the HD stub axles in there, with the bolt-on u-joint caps, instead of the straps/nuts.
My opinion is the diff should be pulled and repaired/rebuilt, with new stub axles/yokes, as Ken says.
One thing I will add, tho...the yokes will rarely line up in use, unless the posi unit is locked/welded. The two half-shafts do spin at different speeds when turning corners, so even if the yokes start out perfectly aligned, they will not still be aligned after a trip around the block.
On a happier note tho...you do have the HD stub axles in there, with the bolt-on u-joint caps, instead of the straps/nuts.
Joel Adams
C3VR Lifetime Member #56 
My Link 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Guess I was referring to the shaft not lining up on each end of each shaft. Not side to side of the diff. Perhaps I mistook what he said in that regard. If both u joints line up in each shaft, than okay. I thought he said they did not. Looking back I did not state that well.
Thanks Joel.
[QUOTE=kstyer]Oh boy, you got some more work to do.
sgm2004 2008-07-14 06:09:51
First, keep in mind the drive shafts are also the support for keeping the rear tires upright. It used the links below the shafts and the shafts to maintain suspension position.
This means there is a lot of stress not only rotational, but in and out stress on the u-joints and shafts as well. The trunions, I call them yokes, have hardened ends inside the diff. These rest on a shaft in the center of the diff called the pinion shaft, not to be confused with the pinion gear.
As the end of the yoke shafts wear, the tops of the tires start to tilt inward when the weight is on the tires.
The wear you see is due to the joint allowing the shaft to hit the yoke due to the joint failing, and allowing play. That is the wear you see. That is cured by replacing the u-joints.
Game still on. The reason you see the gap on both sides of the diff is the fact the shaft ends are worn inside the diff. If you pull on them they will move out a bit. The cure is to replace the yoke/shafts. At least one of them has been replaced by a rookie. That is why they do not line up evenly. The really should line up. The way they are can create driveline vibration and result in more problems and wear. This may have an influence on the problem you have now. You can also get vibration throught the car under certain loads and shaft rpm.
So as you do the joints, it's a bandaid. You need to take the shafts out of the diff, and you will need at least one, if not both, along with the clips that hold them inplace. Replace the side seals in the diff housing at the same time. That also means a gasket and new fluid. Make sure it has the posi additive when refilled.
Yes it get worse. You need to take the spring out to take the diff out, to take it apart and get inside to do the work.
Not what you wanted to hear, but you should do it right to prevent more problems and grief in the near future.
[/QUOTE]
Ken, your right on the money what you just talked about. Above is what I'm going through right now. Left rear side yoke on my 75 just pulled out when I removed the half shaft. Almost got the differential carrier out now. I desided to replace and repair everything in the rear costing arm and leg but never have to mess with it again. Fix it right the frist time. Good luck Jack on yor repairs these guys and gals on this site are great help. Take care
Guy
Ok, I moved the Corvette into intensive care and am ready to pull the differential and the half shafts and take it to someone who knows how to fix it right.
Anyone have instructions on how to pull the differential. I started to work at all the bolts I could see and they are all turning so that's good news.
Anyone know of a good Corvette diffential place in Detroit area?
Lifetime MemberHot Springs, AR - USA
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the part of this that I hate in replacing the yokes is the snap ring on the inside of the yoke.
cthulhu 2008-07-15 19:10:56
i would bet the inner end of the yoke has worn off, causing the snap ring to fall off and then this lets the yoke slide ouf of the diff, which then allows a wierd angle.
also... im not sure what you mean about the 90 degrees thing. they will never stay lined up at 90 degree offset.
When the repair is done Is it not better to replace the yokes with hardened ones, I beleive when mine was repaired that is what was done. a good check for this wear is when the car is jacked up you can grab the bottom and top of the wheel and it will rock back and forth as the yoke goeas in and out, which is bad
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20219
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
[QUOTE=rraider1] When the repair is done Is it not better to replace the yokes with hardened ones,[/QUOTE]
It's always better to go with the best parts, but it really depends on how the car is used. A "driver", or a car that is used often, will benefit from the hardened yokes for sure. If you're working on garage art, or a car that rarely gets any long distance miles, it may not be all that worth-while.
In the long run, however, you really don't want to have to re-do a diff in a Shark more than once in a lifetime, so the better yokes would be money well spent.
It's always better to go with the best parts, but it really depends on how the car is used. A "driver", or a car that is used often, will benefit from the hardened yokes for sure. If you're working on garage art, or a car that rarely gets any long distance miles, it may not be all that worth-while.
In the long run, however, you really don't want to have to re-do a diff in a Shark more than once in a lifetime, so the better yokes would be money well spent.
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
I just had my rear rebuilt from lug nut to lug nut. IT WAS EXPENSIVE! If you need to rebuild, I'd do the t-arm assms too. I didnt when I did mine and Im kicking myself..
in Forum: C3 Driveline Components
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