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Project 1949 Chevy Driveshaft - A Matter Of A PinionThe Project '49 Gets An Aluminum Driveshaft From the August, 2010 issue of Rod & Custom By Kev Elliot
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Using a magnetic protractor... Using a magnetic protractor against the rear face of the transmission tailhousing, I set the output 'shaft angle at 4 degrees. Note the aluminum spacer between the mount and the casing to raise the rear. You probably never give a second thought to the driveshaft under your car-that is until you have to. And although we know a few people who make their own, when it comes time to connect the transmission to the rearend, most of us will either drop the car off at a driveshaft shop or provide them with a few measurements, collect the finished piece, and bolt it in place. There are many times when the driveshaft vibration can be felt in a freshly finished project, sometimes throughout the rpm range, and sometimes at specific speeds. There are numerous reasons and causes, all of which could have been avoided if the drivetrain, and its associated angles, had been planned properly from the outset. A basic rule of thumb when installing an engine is to have the base of the carburetor, or the carburetor mounting surface on the intake manifold, level, which equates to the motor and trans being mounted at an approximate 3-degree downward angle toward the rear of the car. All well and good so far, but how many mount the rearend at a similar angle, this time upward toward the front of the car? This is known as pinion angle, and is extremely important if powertrain vibrations are to be avoided. With the above angles identical, the centerlines of the rearend pinion 'shaft and the transmission will be parallel, though not in a straight line from the pinion to the transmission output 'shaft. An imaginary extension of the trans centerline will pass under the pinion, while the same for the pinion will pass over the top of the trans tailshaft. This is fine, so long as the angle through the U-joints is 3 degrees or less. You can go as much as 5 degrees, or even as low as 0, but according to Greg Frick at Inland Empire Driveline, something between 0 and 3 degrees seems to run smoothest. Though obviously shown once... Though obviously shown once everything was fabricated, I used the same protractor to set the pinion angle on the Currie 8-inch before the axle saddles were welded to the casing. So you can see that mounting the transmission and rearend correctly is important at an early stage of any project, and once finished, the pinion angle should be rechecked and adjusted if necessary. The type of suspension used will offer varying degrees of difficulty when it comes to adjustability. Leaf-sprung cars can have angled shims added between the spring and axle; four-link cars can have the upper and lower links lengthened or shortened. But a ladder bar-equipped car will mean the axle brackets or ladder bar front mounts will need relocating. You may be able to fit a shim between the trans and its mount to lessen the trans angle instead, but it can't be increased! When I installed the motor and trans on our project '49 Chevy I used the engine mounts that came on the Chassis Engineering crossmember, and a Walton Fabrications trans crossmember. The latter is designed to be used with the same company's engine mounts, and the Chassis Engineering motor mounts are higher, so I added a shim under the trans mount to get the trans angle below 5 degrees, settling at 4 degrees. A similar angle was built into the rearend saddles when they were welded to the axle casing. With the drivetrain angles correct, a further problem arose with the RideTech suspension on "full drop", in that the pinion yoke slightly contacted the rear end of the trans tunnel. I elected to wait until the driveshaft was fitted to see just how much of the tunnel would need replacing, despite it having been raised once, several years ago. The point here is to install your driveshaft as early in a build as possible, so as to avoid having to move chassis components or bodywork for clearance. Following Inland Empire Driveline's... Following Inland Empire Driveline's instruction booklet, I measured from the end of the output 'shaft to the flat surface on the pinion yoke where the U-bolts pass through. This measured 57 5/16 inches. I also measured how far (5/8 inch) the output 'shaft extended from the end of the casing. I went to Inland Empire Driveline for my driveshaft, having been impressed with its easy-to-understand literature, and very concise form explaining how to measure for a driveshaft, which can be filled in and sent to the company, who in turn can fabricate a 'shaft to your precise dimensions. Inland Empire can supply 'shafts in steel, aluminum, or carbon fiber, as well as associated components such as yokes, U-joints, U-bolts, and center bearing supports for two-piece driveshafts. It seems at just over 57 inches my driveshaft is a little on the long side, but not so long that a two-piece 'shaft was advised. Also, thanks to my Classic Performance Products trailing arms, and their pivot points a long way from the rearend, the difference in length from the pinion to the trans tailshaft at the upper and lower limits of suspension travel differed by a mere 5/16 inch, though Inland Empire Driveline offers 'shafts with sliding joints, common among the lowrider fraternity with long travel hydraulic setups and short control arms. For more information on when a two-piece 'shaft is required, check out the tech section on our website (search for Two Piece Driveshaft Technology at www.rodandcustommagazine.com), but long spans, limited space (two-piece 'shafts are generally smaller diameter than one-piece), and smoother running all play their part.  Inland Empire's form is very...  Inland Empire's form is very thorough, and to ensure they supply exactly the right parts, the diameter of the U-joint cup is required (1 1/8 inches in my case) ...  While I opted for an aluminum...  While I opted for an aluminum driveshaft, the slip yoke, and 1310 series U-joints are steel, all made by Spicer. These U-joints are allegedly stronger than greasable U-joints and offer an ideal combination of reliability and performance.  Rocky, of Inland Empire, began...  Rocky, of Inland Empire, began the fabrication process by pressing the U-joints and bearing cups into the 6061-T6 aluminum weld yokes ...  ... as is the width of the...  ... as is the width of the U-joint, which turned out to be 3 7/32 inches on my 8-inch axle yoke.  ... before installing the...  ... before installing the snap rings.  Rocky, of Inland Empire, began...  Rocky, of Inland Empire, began the fabrication process by pressing the U-joints and bearing cups into the 6061-T6 aluminum weld yokes before installing the snap rings.  The next step was to machine...  The next step was to machine the tube to the exact length, and put a small chamfer on the inner and outer end surfaces. The tubing was then cleaned inside to ensure no swarf or debris would be inside the finished 'shaft.  The machine included a hydraulic...  The machine included a hydraulic press that presses the weld yokes into the tubing. Rocky left this gap (arrow) to ensure perfect weld penetration.  Determining the tube length...  Determining the tube length had to be 51 3/16 inches, he wrote it on the tube as a reminder then cut it to length. Inland Empire's aluminum driveshafts are manufactured from custom drawn 6061-T6 DOM aluminum tubes for consistent strength. Their products have passed Spicer's grueling dynamic reverse torsion testing, qualifying the company as one of the very few Spicer authorized aluminum driveshaft builders in the world.  With the rear weld yoke and...  With the rear weld yoke and U-joint assembly bolted to one of a number of special yokes manufactured for just such a purpose (remember, the rear U-joint is bolted to the pinion yoke in the car), the weld yokes at each end ready to be pressed into the tube, and the whole driveshaft assembly installed in a specialist machine, which looks like a very long lathe, a level is used at each end to ensure the U-joints are in phase with each other.  Welding aluminum requires...  Welding aluminum requires absolute cleanliness, so the area to be welded is thoroughly prepared using a rotary wire brush on a bench grinder. Note the change in surface texture where it's been cleaned.  Once the welds have cooled,...  Once the welds have cooled, and still on the same machine, the driveshaft is spun up to speed to be balanced. A gauge at each end of the shaft informs the operator of what's required.  Re-installed on the machine,...  Re-installed on the machine, the 'shaft is checked for runout using a dial gauge at each end as well as in the center. Here's where Rocky's years of experience came in, as he knew exactly how to correct the slightest discrepancy.  Again, Rocky's experience...  Again, Rocky's experience came into play as he knew exactly how much weight to apply and where to apply it to perfectly balance the driveshaft. Weights were held in place with wire while the 'shaft was spun again, though they were in the right place first time!  The semi-automated MIG-welding...  The semi-automated MIG-welding procedure ensures strong welds every time. Adjustments are only made when different diameter tubing is used, as it'll rotate at a slower speed. And if you ever wondered how to attach a ground to a rotating assembly, here's how!  With their position established,...  With their position established, the weights were welded in place, a tack at each corner, and a plug weld in the central hole.  Here's why I didn't modify...  Here's why I didn't modify my trans tunnel until I had my driveshaft. Note the difference in diameter between an aluminum 'shaft (3 1/2 inches) and a steel one (3 inches) for the same application. The yokes are larger too, which is where I thought I may have a clearance issue.  With the 'shaft given a brushed...  With the 'shaft given a brushed finish along its length using a Scotch-Brite strip while it was rotating, this strap was added to the open end to ensure the bearing cups didn't stray. It was now ready to ship, or to be placed in my pickup to be precise!  With the new driveshaft installed...  With the new driveshaft installed in the project '49, I was pleased to see it easily cleared the CPP center crossmember, and was of perfect length. Inland Empire suggests 3/4 to 1 inch of the transmission yoke's ground seal surface should show (arrow), with more if the output 'shaft extends past the seal more than the usual 1/8 inch. The Gearstar 200-R4 trans output shaft extends more than double that, so just over an inch showing is acceptable. This is with the suspension at "full drop" with the driveshaft as high in the tunnel as it can go.  Modern Mustangs use a flange...  Modern Mustangs use a flange at each end of their driveshaft rather than a slip yoke at the front, so employ this sliding joint to accommodate suspension movement. Inland Empire can supply such 'shafts.  Two-piece driveshafts require...  Two-piece driveshafts require a center support bearing. On the left is a high-impact polyurethane-cushioned OEM replacement version, while on the right is a 7075-T6 aluminum version for a wide variety of cars, trucks, and utility vehicles, including dualies and especially '58-64 Chevrolets. This "super strength" bearing support is designed to withstand the stress of high-horsepower powertrains.  Another type of sliding joint...  Another type of sliding joint is shown here, used commonly in driveshafts for cars with hydraulic suspension, which see a large discrepancy in 'shaft length at upper and lower suspension travel limits.  Inland Empire Driveline can...  Inland Empire Driveline can supply 1350 forged steel pinion yokes, precision machined for a perfect fit and forged and heat treated for maximum strength. These U-bolt-style yokes are specifically designed for Spicer 1350 use, and are available for a variety of rearend applications.  The U-bolts should not be...  The U-bolts should not be over-tightened. In fact with a bearing cup diameter of 1 1/8 inch, such as mine, they should be tightened between 14 and 17 ft-lb. Over-tightening them will cause drag, leading to vibration.  Once I'd installed the RideTech...  Once I'd installed the RideTech ShockWaves and could set the suspension at "full drop", it became apparent that the pinion yoke very slightly interfered with the rear of the trans tunnel (arrowed). It's shown here in the "fully raised" position with the new driveshaft held in place with tie-wraps, as I didn't have the correct size U-bolts at the time.  When I originally lowered...  When I originally lowered the Purple Pig while it still had a closed driveline, I raised the transmission tunnel as high as it would go without affecting the stock rear seat base.  Luckily, I only had to raise...  Luckily, I only had to raise the rearmost 6 inches of the tunnel to provide clearance for the pinion yoke and weld yoke on the driveshaft, the remainder of the shaft easily clearing the tunnel on "full drop". As the rearmost section is behind the rear bulkhead, the stock seat base will still fit! With the tunnel modified I can now fit my finger between the yoke and bodywork with the rearend on the bumpstops.
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