By replacing an old worn straight-six motor with a 300-plus horsepower motor you will likely wear out the stock transmission and, more importantly, the stock rearend. We will save the transmission for another story and focus on the rear housing of '55-59 Chevy chassis. Rear axles and housings tend to confuse a lot of people when searching for what they think they need, but what you think you might need and what would work best for your application just may be two different things. Will a full locker work for a normal street truck or 28-spline axles for drag racing? Maybe they will, but in a practical application a locking rear differential will wear out your rear tires prematurely in a daily driver, and the strength of 31-splined axles are no match for the 28-splined nontapered stock axles.
So to take some confusion out of the equation I made a phone call to Currie Enterprises of Anaheim, California, and asked if they could share some of their years of experience and knowledge of rear axles. Brian at Currie Enterprises invited me to take a shop tour and show me the process of how a normal order would make it through the shop. Walking around their giant warehouse full of axles and housings I noticed one thing right away: This is all they do. Countless employees were working away and Brian pointed out that each employee has a very specific job to perform in order to complete a single housing. This means one employee will machine the tubes to length and another will set and tack-weld them on, while a qualified welder will finish welding the tubes in place. This assembly line style of housing production ensures each employee knows that part of the build very well.
I started my order with Currie knowing that my stock axle on my Chevy Fleetside was 63 inches wide from end to end. I also knew that I would be putting the much wider 8x16 rear wheels from Wheel Vintiques and 205/60R16 American Classic 11/2-inch whitewalls from Coker Tires. Measuring for a replacement Currie Enterprises rear axle is really straightforward if you know what to look for. The first thing I look at is the wheel placement in relation to the outer fenders and framerails. Also, look for the bedwood on the inside of the fenderwell. After you measure and are happy with the overall length of the housing you will need to figure out your pinion offset. The pinion offset is the rearend input yoke's side-to-side relation to the driveshaft and the transmission. If your transmission's rear yoke is offset then you will need to measure the pinion offset to match. Otherwise the rearend, driveshaft, U-joints, and transmission will suffer from the extreme angles and misalignment. In my case the pinion offset was zero and the overall housing length from end to end was measured at 621/4 inches.
