|
|
Driveshaft Rebuild - ShaftedThe driveshaft is often the forgotten link of your vehicle. This month we'll show you how it works and how to keep yours from breaking. From the September, 2011 issue of Mopar Muscle By Dave Young Photography by By The Author
|
|
As automotive enthusiasts, most of us are familiar with the parts needed to make an engine more powerful, a transmission shift harder, or even the rear axle gear ratio required for maximum acceleration. But what about the link between the transmission and the rear end, the driveshaft? Because the driveshaft can't really enhance the performance of our vehicle we often forget about it, just assuming it will do its job until something bad happens. And when bad things happen to a driveshaft, yoke, or universal joints, your drive can get disastrous in a hurry. At the very least, a driveshaft problem will leave your vehicle stranded, and at worst can lead to transmission and rear end damage, or loss of control of the vehicle. For these reasons, the driveshaft is one part of a Mopar where preventive maintenance pays off. As you'll see in our Hidden Treasures column this month, we recently purchased a groovy '78 Dodge Tradesman 200 California show van. As a running and driving vehicle, we made the trip from Ft. Myers, Florida, back to Lakeland, Florida, without much incident in our new purchase, but noticed a moderate vibration coming from the van's drivetrain. While driveline vibrations can have a variety of sources, experience told us that this vibration was coming from either the driveshaft, transmission or pinion yoke, or one of the universal joints. It's really no surprise that problems occur with the prop shaft, or driveshaft of a vehicle, especially one that's used in a high-performance application or hauls heavy loads. Every time you drop your car into gear or let the clutch out, the driveshaft is absorbing the torque of the engine and transferring it to the vehicle's differential. Each time you accelerate or decelerate, the driveshaft and its related components are loaded and unloaded, and it happens countless times during a normal drive. The bearings inside the universal joints take a beating as well, since the driveshaft spins at thousands of rpm each time the vehicle is driven. Add a smoky burnout or two or run over some debris, and the shaft itself can become bent and out of balance, which will eventually lead to universal joint failure or premature wear of the pinion bearing of the rear end, or the output shaft bearing or yoke bushing of the transmission. In our case, we weren't sure what was causing the vibration in our van as the universal joints seemed to be tight and in serviceable condition. While under the van, however, we did notice several dents in our driveshaft indicating it could have been damaged by road debris. Since the driveshaft spins at a relatively high rate, a bend in the driveshaft can cause a pretty severe vibration which can only be repaired by straightening and rebalancing the shaft, or re-tubing the driveshaft altogether. With this in mind, we pulled the driveshaft from the vehicle and took it to our local driveshaft shop, Central Florida Driveshaft, to have it repaired. Once at Central Florida Driveshaft, the staff placed our shaft in one of their driveshaft lathes to check it for straightness and balance. Spinning the shaft on the lathe, it was quickly apparent that our driveshaft was severely bent and would require major repair. In some instances the shaft can be straightened, but in our case the driveshaft would have to be cut apart and rebuilt with a new tube. Fortunately, Central Florida Driveshaft has new driveshaft tubes, ends, universal joints, and even yokes to make repairs easy. For our driveshaft they recommended replacing the tube, and to save us a few bucks they offered to use a second-hand tube that was in good shape. In addition to rebuilding driveshafts, most driveshaft shops can shorten, rebalance, and repair driveshafts in addition to installing new universal joints. On other project vehicles we've even had them make a driveshaft from scratch based on our measurements.  1 We picked up this ’78 Dodge...  1 We picked up this ’78 Dodge Tradesman van as a cool driver and inexpensive alternative to typical A-, B-, and E-Body Mopars. The van’s 360 runs good, and the vehicle is in overall great shape, but we noticed a driveline vibration that needs to be addressed before it causes damage. Narrowing the problem down to the driveshaft, we decided to pull the shaft and take it to our local shop, Central Florida Driveshaft, to be rebuilt.  2 Always set the parking...  2 Always set the parking brake to keep the vehicle from moving—or in our case, a wooden block. Remember that “park” gear will only hold the vehicle if the driveshaft is in place. Also, place a drain pan under the transmission tailshaft to catch any transmission fluid once you pull the slip-yoke out.  3 Having an extra 727 slip-yoke...  3 Having an extra 727 slip-yoke around is helpful as it can be installed to prevent leaks and to keep dirt from getting in the transmission while the driveshaft is being repaired. This is one we shattered in one of our race cars, but it still works for our purpose here. Unlike the local parts store which may only offer one choice, most driveshaft shops keep a variety of quality parts in stock, including American made universal joints. Mopars used two distinct sizes of u-joint, commonly referred to as the big and small u-joint. Since often a rear differential swap results in a pinion yoke that doesn't match the driveshaft, most driveshaft shops offer adapter u-joints which go from one size to the other, saving the time and expense of changing the yoke or driveshaft. Central Florida Driveshaft offers same-day driveshaft service in most cases, ensuring your ride isn't off the road any longer than necessary to complete repairs. Since our driveshaft needed to be rebuilt with a new tube, we followed along to show you what is involved in rebuilding a Mopar driveshaft. After it was initially determined that our driveshaft was pretty severely bent, the team at Central Florida Driveshaft quickly cut the ends off of our old shaft and found a secondhand driveshaft that was in good shape to use as a replacement. Since the majority of driveshaft damage occurs at the ends, mostly due to abuse and worn-out or dry u-joints, longer shafts can be cut down and used in shorter applications by welding on new ends. Having the right equipment is necessary to keep the driveshaft aligned and straight during the rebuild process, and the driveshaft must be rebalanced once the work is complete by welding weights to the outside of the shaft. The crew at Central Florida Driveshaft completed the work on our driveshaft and installed new, American made u-joints in a couple of hours. And after reinstalling our repaired driveshaft, our van drives great with no more vibrations. Now we can concentrate on getting our cool cruiser ready for this year's Hot Rod Power Tour by searching the internet for a disco ball, fender flares, TV aerial, and side pipes! While we were at Central Florida Driveshaft we asked what the most common driveshaft failures were. According to the staff, lack of proper lubrication is the single largest cause of the failures they see, with abuse being a distant second. As you can see from the above examples, bad things can happen when a universal joint comes apart, and adequate lubrication can stop most failures. Central Florida Driveshaft recommends the u-joints be greased at each oil change and checked regularly for sloppiness or wear. If a problem is caught in time, it will require simply having new universal joints installed. If not caught in time, the problem could lead to failure of the u-joint and driveshaft and damage to other components of the vehicle or even injury to occupants. So, when's the last time you lubricated and inspected your u-joints?  4 Once removed, be sure to...  4 Once removed, be sure to hold the caps on the rear u-joint by wrapping tape around the u-joint and driveshaft. Failure to do this can result in the caps falling off and the needle bearings being scattered about the floor. If this happens, it’s difficult to find all of them or get them back in the cap properly, so it’s easier just to tape the u-joint.  5 Once removed from the vehicle,...  5 Once removed from the vehicle, we could see several dents in our driveshaft, likely caused by running over some major debris. Though it is possible to straighten driveshafts that are slightly bent, we think this one will need to be re-tubed.  6a After removing the slip-yoke...  6a After removing the slip-yoke from the front of the shaft...  6b ..The driveshaft is placed...  6b ..The driveshaft is placed in a specially made lathe where it can be checked for straightness and balance.  7 As soon as our driveshaft...  7 As soon as our driveshaft began to spin, it was apparent that it was too severely bent to straighten. The only option here is to cut the ends of our existing shaft and install them on a different tube.  8 Luckily, Central Florida...  8 Luckily, Central Florida Driveshaft keeps various sizes of new tubing in stock, as well as a variety of old driveshafts with varying levels of damage. They saved us a little money by cutting the ends off and shortening a used driveshaft so they could install our ends.  9 The driveshaft ends can...  9 The driveshaft ends can now be fitted to the new (or in our case, used) tube to ensure a proper fit prior to welding. The driveshaft is actually three pieces, a center tube and two ends, that are welded together to form the driveshaft.  10 Once the ends are fitted,...  10 Once the ends are fitted, the shaft is placed in the lathe again where the ends are welded in place. This is somewhat of an art as the driveshaft is turning at a low rpm, adding one more variable to the welding process.  11 With the ends welded,...  11 With the ends welded, the shaft can be balanced using equipment installed on the same driveshaft lathe. This is a specialty piece of equipment, allowing complete driveshaft servicing and repair on a single piece of equipment to save time.  12 The dynamic balancing...  12 The dynamic balancing a driveshaft is very similar to balancing automotive wheels and tires. As the shaft is spun, the balancing unit determines how much weight is needed and in what location.  13 Weights are initially...  13 Weights are initially held in place with tape while the driveshaft is spun for balancing, then once the best balance is achieved they’re tack-welded onto the shaft. Central Florida Driveshaft balances their shafts to better than OEM standards, ensuring each driveshaft operates smoothly. If we install this driveshaft and have a vibration, we should look elsewhere for the source.  14a Balanced and ready for...  14a Balanced and ready for service, Central Florida Driveshaft installs new universal joints and the slip-yoke, then liberally greases the u-joints using the installed grease fittings...  14b ...Most universal joints...  14b ...Most universal joints have a grease fitting either in the body or in one of the caps. We prefer the fitting in a cap so that the body of the u-joint isn’t compromised by the hole.  15 As a final step the driveshaft...  15 As a final step the driveshaft is painted, making our used tube look far better. New driveshafts are painted as well, both to inhibit rust and for aesthetic purposes. With this final step complete we’re ready to reinstall our shaft and take the van for a cruise.  16 Trucks and vans are nice...  16 Trucks and vans are nice because you often don’t even need to jack them up to complete jobs like this. We had our driveshaft installed in a few minutes and were ready to go for a drive.  17 Our groovy van now cruises...  17 Our groovy van now cruises comfortably with no driveline vibration thanks to the new driveshaft. This is just one of many maintenance items we’ll take care of before driving our new purchase in this year’s Hot Rod Power Tour.
|
|
|