How to Select and Order Custom Length Driveshaft Kits
A Custom Driveshaft the Easy Way
Over the last hundred years or so, hot rodders and racers have invented an almost endless combination of cars, engines, transmissions, and rear axles. Whether it’s a solid lifter small block in front of a Muncie in a ’32 Ford or a turbocharged LS and T56 stuffed into a Vega, we’ve done it all. And when the dust has settled and all the custom fabrication and clever shoehorning is complete, every project (at least every project being driven by the proper pair of wheels) is going to need a driveshaft. Until now, that meant finding a local driveshaft shop and either hoping they understand the measurements you’ve given them sketched out on a napkin or trailering your project to their shop and leaving it with them to make and install a driveshaft. Neither situation is ideal. Speedway Motors has solved this problem with our Custom Length Driveshaft Kits. We’ve taken away all the guesswork (and the need to borrow your friend’s car trailer). Simply take a few measurements as detailed in this article, place your order, and a few days later a custom-made driveshaft will be delivered to your door.
Speedway Motors Custom Length Driveshaft Kits
Speedway Motors offers several custom length driveshaft options. There is a version made from 2-1/2” OD tubing that is available in lengths from 11-50 inches in ½” increments. These are suitable for applications up to 400 horsepower. The 3” tube kit is available in ½” increments from 16-58 inches and will support up to 600 horsepower. If your application calls for something a little longer, our 3-1/2” kits are available from 30-70 inches and are also good up to 600 horsepower. Finally, if you’re really making some power, we offer a 3” tube kit made from 4130 Chromoly that will handle up to 1200 horsepower. Chromoly kits are available in lengths from 16-58 inches.
If you prefer to take matters into your own hands, Speedway Motors also offers U-Weld-It kits. These are available in 2-1/2 and 3 inch diameters with various u-joint options and offer an inexpensive alternative to anyone with a saw and a welder. We used one of these kits when we dropped the 383 and Tremec 5-speed into our Project Chevelle. After making the initial cut, we delivered it to the machine shop to be squared up on the lathe and welded by a certified welder. If you’re at all uncertain, it may be worth the extra effort to get some help from a pro for this step.
How To Measure for Length
This is the most critical part of your driveshaft order. The wrong yoke or u-joint can usually be swapped or adapted, but there’s no easy way to change the length. With that in mind, we’ll show you exactly how to measure here.
One of the hardest things about dealing with a driveshaft shop is making sure that everyone’s using the same reference points. Simply indicating that you want a 31-inch driveshaft is not good enough. Is that 31-inches from u-joint center to u-joint center, or is it the overall length of the driveshaft? It can get confusing. Speedway Motors makes it easy. The measurement you indicate on your order is simply the center of the rear u-joint to the seal surface on the tailshaft housing if your transmission. Here’s what that looks like:
We don’t need to tell you to be safe when you’re under the car to measure. Use plenty of jack stands and make sure everything is secure before you even think about crawling underneath. With that done, the next important consideration is the height of the rear axle. It is very important that the rear axle is at ride height when measuring for a driveshaft. If it’s hanging because the car is in the air, then your measurement will be inaccurate and your driveshaft will be incorrect for your application.
When you’re ready to measure, your reference point on the rearend will be the flat face on the rear yoke. That surface coincides with the center of the u-joint when it’s installed. On the transmission side, measure to the seal surface on the back of the tailshaft housing. Don’t measure to the splined tailshaft itself, which typically protrudes from the housing. Doing so will cause your measurement to come up a little short. Not only is the seal surface an easy place to measure to, it also saves the guesswork of installing the yoke and guessing how much engagement you should have.
Selecting the Right Yoke and U-Joints
These driveshafts arrive ready to go. That means that the u-joints and yoke are already installed, ready for you to bolt up and hit the road. If you have any questions about which yoke and u-joints you need, the information below will be very helpful:
Yokes:
GM: (T350) GM 27-spline, 1.5-inch OD Seal: Fits TH350, Aluminum Power Glide, 700R4, 200-4R, 4L60, 4L60E, 4L65E, 4L70E, Muncie M20 & M21, Saginaw 3 & 4-speed, T-5, T-10, T-56 (T400) GM 32 spline yoke: Fits Turbo 400 (with no threaded hole in output shaft), Muncie M22, Super T10, 4L80E, 4L85E
Ford: (C4) 28-spline: Fits Ford C4, C5, AOD, AOD-E, Ford T-5, T-10, Top Loader, TR-3550 (C6) 31-spline: Fits Ford C6, FMX, E4OD, 4R100, ZF 5-speed, TR-6060
Chrysler: (7290) 30 Spline: Fits 727, A833** **A833 manual transmissions were produced with both 26 and 30 spline output shafts. Count the splines on your output shaft before ordering.
Aftermarket Tremec: Tremec T-5, select Ford (C4) 28 spline Tremec TKO, TKO-500, TKO-600, T-56 Magnum, Magnum-F, TR-6060, select Ford (C6) 31-spline
U-Joints:
GM & Ford: (1310) 1-1/16-inch cap X 3-7/32-inch wide (1330) 1-1/16-inch cap X 3-5/8-inch wide (1350) 1-3/16-inch cap X 3-5/8-inch wide (3R) 1-1/8-inch cap X 3-5/8-inch wide with inside snap ring (FS) 1-1/8-inch cap X 3-5/8-inch wide
Chrysler: (7260) 1.078-inch cap x 2.125-inch with inside snap ring (7290) 1.126-inch cap x 2.290-inch with inside snap ring
How to Order
When you’ve figured out what u-joints, yoke, and length you need, you’re ready to place your order. If you would prefer to place your order on the website, the video below is a helpful walk-through showing how to enter your information and make sure that your driveshaft is perfect for your application.
As always, if you have any technical questions or prefer to place your order by phone, give us a call at 800-979-0122 to talk to our helpful sales and tech staff.
