By Brian Martin
One of the most common questions we get asked is “Do y’all stretch frames?” When it comes to “style,” wheelbase is often a BIG piece of the puzzle. In many cases, a longer wheelbase is an upgrade that is required to haul certain types of freight such as steel beams, poles or trusses.
There is no real trick to lengthening frame rails. Some folks build it up to be much more scientific and intense than it really is. The only tools a guy needs to do the job are an acetylene torch or plasma torch, an electric grinder, a few jack stands, hydraulic jacks or screw jacks, good welding equipment, a tape measure and a string.
Basically there are two ways to lengthen the chassis of a truck. You can cut it in the middle and add the additional frame in the middle of the truck, thus requiring two joints or welds. The other method is to add rail to the rear of the truck, unbolt the suspension, roll the suspension back and remount it to the rail, which would require only one weld.
Many idealists argue that the likelihood of any future frame failures is far less likely with the “one weld” procedure. I agree that the integrity of the chassis would be somewhat better with one weld, rather than two. However, I assure you that if it is done correctly, both methods will last a lifetime with no issues and no headaches.
The “cut in the middle” method is usually a less costly job, due to fewer labor hours being required, and in our shop over the last 20-plus years, we have seen zero failures.
Seems like 80 percent of the frame jobs I see are “straight” cut. The mechanic simply makes a straight cut from the top of the rail, straight down to the bottom of the rail. There is nothing wrong with this method, and I have rarely seen a crack or failure.
We still prefer to do an angled cut here at Chrome Shop Mafia. Starting at the top of the rail, we cut downward about one-third of the way, then angle downward and diagonally forward for another third, and then cut straight downward to the bottom of the rail.
Our philosophy is, this creates more weld and multiple directions of the weld, which by design should equate to added strength for more peace of mind than the “blunt cut” butt weld method. But, let it be known by all, that we can live with either method. We just prefer the latter, as it causes us to sleep better at night knowing our stuff is a bit “over-done” and well above the minimum requirement.
One absolute must-do, regardless of the style of your cut: The edge of the frame rail that is about to be welded must be dressed up so that both edges are beveled off to a 45 degree angle with an electric grinder for better weld penetration. Lastly, make sure you have a good hot welder. Whether it is wire feed or stick weld really isn’t as important as making sure the voltage/heat is adequate to get a good solid weld.
Visit your local salvage yard and buy some rail that matches your truck, a cross member and a piece of driveshaft that is compatible. Slice the baby in half; cut the frame pieces that will be added to your truck; grind everything until it fits up nicely; pull a string line down the top and down the sides of the rail to ensure everything is true and plumb; tack weld it together. Then weld her up good and solid, welding 2-3 inches on one joint then moving to another joint while that one cools to prevent excessive heat and warping.
Generally we bolt a steel “liner rail” inside the outer frame rail and make sure it extends 24-30 inches past each weld, then add one additional cross-member in about the middle of the added frame rail.
Most any frame job will require the addition of at least one more driveshaft with a carrier bearing. Try to keep all your driveshafts comparable in length, with no shaft exceeding 72 inches from center of yoke to center of yoke.
Another rule of thumb is to make sure that you maintain a working driveline angle of 2-5 degrees at any U-joint. Common sense may tell you to keep them straight at a zero-degree working angle, but for a U-joint to perform as it is designed, some angle will be required.
Obviously, all us truck junkies realize this is the abbreviated version of frame stretchin’, but hopefully it lays down the basics. After tons of experience, it has worked for us. Our ancient Mafia proverb says: If it ain’t broke, don’t change it.
There ya have it, gang. So until we chat again … may the Truckin’ Genie grant us just one wish: That we wake up tomorrow and CARB would choose to work with us instead of against us. An occasional puff of black smoke don’t necessarily mean it’s broke. LL