Just came back from the alignment shop and I am very happy with the results using Duke's recommended radial tire specs. When the car was on the alignment lift and the Hunter aligment "heads" were being attached to the rims - we noticed quite alot of in/out movement as the tire was moved top and bottom toward and away from the car (no load on tires at that point). I looked under the car and saw the the differential yokes appeared to be moving in and out by 1/4" or more on both sides. I know the half shafts are a stressed part of the rear suspension design - but does that much motion seem normal ?
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Re: Half Shaft - In/Out
Peter-----
1/4" lateral movement of the yokes, if it actually is that much, is not only excessive, it's cause for immediate repair. The most that there should be is about 1/16". Most likely, the problem is caused by worn yoke ends, a very common 63-79 Corvette malady. It's also possible that a worn posi clutch pack could be contributing to the problem, but I'll bet that you find the yoke ends severely worn.In Appreciation of John Hinckley -
Re: Half Shaft - In/Out
Peter,
You didn't state what year you had but the problem is most common with 1978 and 1979 Corvettes. Chevrolet just decided that the shafts didn't need all that expensive hardening.
Don't panic but I would be worried about all the powdered metal from the shaft ends and the C-clips that used to hold the shafts tight. The oil and the metal shavings have a negative effect on the ring and pinion as well as the bearing.
Time for a rebuild!
Regards,
JRComment
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Re: Half Shaft - In/Out
Joe/Ray - Are new differential yokes avaiable to match exact original specs and if so - where do I get them - GM Restoration Parts ??Comment
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Re: Half Shaft - In/Out
Peter,
New ones are available from Lonestar at 1 903 829-8400, Bair's at 1 814 683-4223 or Ikerd's at 1 812 279-4828.
Regards,
JRComment
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parts to replace
The yokes are available new to factory specs or you can buy rebuilt ones with a pressed-in hardened tip. While there, also check the pinion shaft for wear.
Good luck,
MarkComment
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Re: Half Shaft - In/Out
Peter-----
For these yokes, I think that a quality rebuild is better than a new reproduction yoke or, even, an NOS GM yoke. The new yokes all have a case hardened end. The case hardening is really quite thin. When it wears through, the wear rate then progresses very rapidly. That's how yours lost, apparently, 1/4" off the inner end.
The rebuilt yokes have a through-hardened "button" installed on the inner end. This "button" replaces the last 1/2" to 1" of the splined yoke. The through hardening means that instead of, say, 0.050" thick of case hardening, you have the full thickness of the button hardened to a very high Rockwell harness. No strength is lost because most of the length of the button is inboard of the spider gears (especially if you get rebuilt yokes with buttons that are about 1/2" thick). So, you get the best of both worlds: an axle as strong as original with a end that will NEVER wear through.
Now, to be quite frank, the reproduction axles as manufactured by Lonestar and others will probably last much longer than anyone of us are ever going to need them. However, I still like the rebuilt axles better for the reason I described above.
If I were going to use new axles, though, I would strictly use those manufactured by International Axle of Dayton, MN. In my opinion, these are far-and-away the best pieces out there. They're a lot more expensive than the others, too. That's because they are a lot better than the others. If I were going to install NEW axles, I would forego any of the many NOS GM axles that I have [none for sale] and use the International Axle pieces. Absolutely. Positively.In Appreciation of John HinckleyComment
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Re: Half Shaft - In/Out
Joe - Based on your recommendation - if I understand this right - reconditioned original is the best way to go, That said - I just checked Van Steel and they offer reconditioned for around $90. I have 1966 427/425 with 3:70 posi rear. Are the side yokes the same for SB and BB ?Comment
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Re: Half Shaft - In/Out
No. The BB yokes use caps, while the SB yokes use straps. Also, while you have it apart, replace your spider gear pin, and your retainer clips.Comment
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Re: Half Shaft - In/Out
Joe, I have the same problem with the inner drive shaft yokes on my '74 as Peter. It too was discovered during an alignment I had done last week and I would estimate the movement is almost 1/4 inch. Since everything has to come apart anyway, is there anything else besides the spider gear pin and retainer clips that I should have the mechanic check? Also, under normal driving, how long should the yokes last? The car has 86,000 miles on it and I thought these were replaced by the previous owner about 36,000 miles ago. Thanks, BillComment
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Re: Half Shaft - In/Out
Bill-----
When replacing the yokes, the best thing to do is to have a complete overhaul by a competent and experienced professional. In general, all bearings, posi clutch pack, and small parts will be replaced. Beyond that, whatever is found to be worn or defective in the rebuild process will need to be replaced.
The problem with the Corvette yoke axles is the case hardening of the ends. Many, especially those produced from the later 70's to about the mid 80's, had highly deficient case hardening. Once the case hardening wears through, the axle ends will wear at a VERY fast rate. The shaft which they contact and wear against is hardened to a VERY high Rockwell hardness and it rarely wears more than a "smidgeon".
36,000 miles would be considered a very short life for these things. However, if they were deficient as to end case hardening, they could go in that time. 1/4" end play indicates that they're VERY worn.In Appreciation of John HinckleyComment
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Re: Half Shaft - In/Out
Bill:
The easy answer is that, if you want to avoid or delay the big job of removing your differential from the chassis, then do everything that you can with the unit in place. Includes everything that I previously said, plus, you can also remove and CAREFULLY tap in new side seals, since they are probably very brittle by now.
If the posi unit is working correctly, the ring/pinion are quiet, the pinion seal does not have a MAJOR leak, AND the car was never abused, then the rear axle requires very little, if any service.
JoeComment
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