Mailbag: How to Identify Your GM 10-Bolt Axle

Q: I have a 1964 Chevy II/Nova with a 194 cubic-inch straight-six engine, Powerglide, and a 10-bolt rear-end. I’m trying to identify the 10-bolt rear axle — I want to know if it is a posi or not. There are no ID tags anywhere. Usually only one tire spins, but sometimes both do.

Also, I notice a mysterious whining sound when driving at a steady pace; the sound is loudest between 35 and 55 miles-per-hour. Could this be coming from the rear axle or do you think my transmission is going bad?

A: The rear axle identification code can usually be found on the passenger-side axle tube, midway between the brake backing plate and the carrier housing. The code is stamped on the tube and is very hard to read unless you wire brush all the road gunk off of it. The ID code for your 3.08-geared 10-bolt is DB for open and DH for positraction. We’d say you have the open-style rear axle.

This listing from the NovaResource website has a more extensive breakdown.

Image courtesy of NovaResource.org

As far as the whining sound, it’s hard to tell whether it’s your rear axle or tranny.

We’d start by inspecting the pinion seal on the 10-bolt for leakage. We’d also check for excessive slop on the pinion shaft when you put the car in gear. This could be causing the noise, assuming the U-joints are okay. You may also want to drop the transmission pan and inspect for any obvious damage. Replace the filter while you’re there, too.

…

This is another in a series of weekly Q&A Mailbag sessions with Summit Racing‘s tech department, in which there are hundreds more. Click here to see them all.