The rear wheel bearings on ’65-’82 Corvettes present more of a service problem because of their substantial interference fit to the axles and the use of specific shims rather than an adjusting nut to set clearance. When we say "substantial" press fit, we mean it. I’ve watched technicians try to disassemble the rear bearing stack using a hydraulic press capable of 20 tons pressure. I once even saw a guy, pushed to desperation, break the cage off the rollers, then remove the inner bearing race with a cutting torch–yes, my friends, the flaming hack saw–and he did it without damaging the axle.
Whether you are successful in removing the old bearings or need to buy new axles from Chevrolet (p/n 3872476); we suggest reducing the diameter of the bearing locations such that the 20-ton press fit becomes a tight slip fit requiring only stout smack with dead-blow hammer to install the bearing and a small press to remove them. The amount material you remove is about .0003 in., (that’s three ten-thousandths of an inch). This is best done with a strip of medium grit sandpaper. Standard Abrasives Motorsports, 240-grit, 2 in. wide Handy Rolls work great except for their 50-yard lengths. Hopefully you can find a retailer who will sell you a strip a couple of feet long for your axle job. Spin the axle with the lathe. Hold the strip tightly at both ends then apply the center to the axle.
However, do not just cut the axles down .0003 in. and put the bearing stack together. Our measurement is only a starting point. Cut the axles to near our figure then try on the bearings. If the fit is still tight; "trial-and-error it" until you get it right. Use caution, if you cut too much; you buy more axles. You will need a vernier or digital micrometer to make the measurements.
After the shaft diameter reduction; check the flanges as they, also, have a part in the cumulative run-out problem. We’ve seen as much as .003 in. on brand new parts–all it takes is some errant, warehouse wonk dropping a box containing an axle. Used pieces? Doug Norrdin told us they can be worse, as much as (gulp) .010 in. run-out!
There is no factory spec for axle flanges, but we feel maximum acceptable is .002 with 0-.0005 desirable. To measure this properly, the axle should be indexed in a lathe, then the flange run-out measured with a dial indicator. In our case, the two new axles we ordered from Chevrolet each were perfect…zero run out.
If you find run-out more than .002; remove the wheel studs, then have a machinist true the outer surface of the axle flange. If the axles are new, reinstall the studs; if you are reusing your old axles; install new studs.
Chevrolet cites a rear wheel bearing clearance range of .001-.008 in. and further states that, if the clearance is within those specs; adjustment is unnecessary. Not. That’s a really dumb recommendation. If you have bearings near the factory-accepted maximum, your brake disc run out is .004 and your axle flange is off by, say, .003 (.007+.004+.003 equals, ah–.014); you’d have an air pumping problem. That large range makes us wonder if, back in the old days, the folks writing these specs were aware of air pumping and if they ever drove or fixed Corvettes.
The ideal situation is to set the rear bearings at .0005-.001. However, since Chevrolet only makes the shims available in .006 in. increments (again, people making decisions long ago didn’t drive or fix these cars–thank god they’re retired), there’s only a slim chance that you’ll hit the magic number. The solution? Adjust the thickness of your rear bearing shims such that they become "specific-fit" devices and rear bearing clearance ends up .001-in.
Use the existing shim as a base line. Assemble the bearing stack, but leave out the inner and outer seals and do not pack the bearings. Add the inner u-joint flange and tighten the nut.
As you tighten the nut, you must constantly feel for bearing tightness by rotating the carrier as you pull down the nut. The reason for this is, if your shim is too small, the bearings will reach zero clearance before the nut reaches its suggested torque figure of 100 ft/lbs. It that happens; you can destroy the bearings. If the bearing tightens up before you reach 100 ft/lbs. Stop! Find out what’s wrong, first.
If all is well, once you’ve got the nut at 100 ft/lbs, measure the clearance. From that number, subtract .001-in. then add the result to your existing shim. If that sum is the same as an available shim (1-in-6 chance, you lucky dog, you!), install that shim and recheck the clearance. Example:
.007 measured clearance .127 existing shim (p/n 3820228)
-.001 desired clearance -.006 clearance reduction
.006 clearance reduction .121 desired shim (p/n 3820229)
If the sum is not the same as an available shim, pick the shim of the next larger thickness above your computed, desired shim and use a surface grinder to reduce the thickness of that unit to the thickness called for by your computations. Examples:
#1 .008 measured clearance .127 existing shim (p/n 3820228)
-.001 desired clearance -.007 clearance reduction
.007 clearance reduction .120 desired shim
#2 .121 next larger shim (p/n 3820229)
-.001 surface grind
.120 desired shim as in example #1 above
Check the clearance. If it’s correct, disassemble the stack, pack the bearings, install the seals and reassemble all this per the Service Manual. We recommend Loctite 242 to lock the bearings to the axles.
This trick works well in limiting bearing clearance and is very durable. In the case of the Big-Block from Hell, the rear bearing clearance had been set by its owner, using the above method, to .001, ten years and 20,000 miles previously and the chart we presented earlier show that the clearance held throughout that period.
All that was necessary during the work Global West did on this car, was to knock the Timkin bearings off the axles, clean and inspect them, repack the bearings, install new oil seals, Loctite the bearings and reassemble the bearing stack.
