After learning of the difficulties finding RW507GR rear axle bearings, I sent an email to Timken and received the following response. I thought others might find it interesting so I am sharing it despite the obvious issues. Thanks Alan for your inquiry. These cars were produced when I was still in grade school, so I had to do some research. The bearings you have are ball bearings. Timken has never produced a ball bearing, but did offer them as part of their full line offering. I am not sure who they were purchased from at the time. Neither Federal Mogul or SKF have a public record of them I could find. BUT, what I did find is in 1967 GM had a first design, (RW507GR) and a second design, (RW508BR). From what I could find, specs are close but not interchangeable. The RW508BR is a bigger overall bearing. My guess is the RW507GR bearing or axle was not holding up. I am wondering if the axles are interchangeable within the differential housing and gears. If the newer design axle could be used you could use the RW508BR bearing. I am sure it would require other components as well, and maybe some changes. I dont know. It appears the RW508BR is still in production, or at least there is some inventory. With this said, The information we share with you, is to the best of our knowledge accurate and safe. Timkens position is to only replace parts with parts approved by the O.E. manufacturer. The information we share in many cases comes from customers such as yourself who have found will fit substitutes which satisfy their needs. In some cases, customers have made modification to vehicle components. Under no circumstances should a product made by Timken, or made by someone else and offered by Timken, be modified in any way. No exceptions! Should you decide to follow the information passed along in this email, you accept all responsibility for the outcome. There are many aspects which we have no control over during the assembly and use of Timken product such as, but not limited to, condition of the parts which are not Timken. Timken has no control over the qualifications of those working on the vehicle including the level of competency. Once again, Timkens position is to only replace parts with parts approved by the O.E. manufacturer. The specs for the RW508BR are Bore = 1.5312, Outer Diameter = 3.062, and Width = .776 The specs for the RW507GR are Bore = 1.4370, Outer Diameter = 2.891, and Width = .740. The specs for the RW507GR came from the web. I can't guarantee the accuracy. The specs for the RW508BR came from data I have here at Timken.
Al, Take out your 8.2" and install a 71-2 Skylark 8.5" You will have better selection of parts and much cheaper to build. You will need to shorten your d-shaft 7/8"
George, I've read that if this is done, one would need to have about 4.5" of backspacing on the wheels. I have a set of jj 15x7 buick rallye wheels. Can those be modified to provide the necessary backspacing or will a set have to be made to order? Thanks. Alan
