In the last write-up on this car we executed a large suspension transformation that resulted in a significant improvement to the car’s handling capabilities. It removed the nose dive on braking and the exaggerated squat on acceleration. The changes brought the ride height to a reasonable level and provided roll stiffness that vastly improved the steering response and road feel.
Much of the improvements were things that eliminated the overly compliant factory bushings and inadequate factory bracing. With the additional stiffness and more precise locating of suspension points came indicators of the wide tolerances typical of a mass produced drive train. This manifested itself as some drive train clunks, particularly between the transmission and rear differential.
The owner and I had considered what options were available. Some that occurred to us unfortunately would be a substantial financial investment. So the owner did a lot of research and came up with a modification that would prove to be nearly miraculous. His research uncovered a company called Shaftmasters that produces replacement driveshafts for 2005 and up Mustangs. They convert the heavy two-piece steel stock shafts to a single-piece light aluminum version.
Certainly there are other companies out there with similar options, but this outfit’s solution is particularly attractive because it uses neither adapter plates nor flanges that can easily be installed out of alignment. I have plenty of experience with driveshafts that use those methods and it can be very tricky to line up without misalignment occurring. The Shaftmasters drive shaft is a direct bolt-in design where alignment is not a variable.
I was particularly impressed with the quality of their driveshaft when I unpacked it in preparation for installation. The welds and finish were excellent. It was also impressive that they packed a set of replacement bolts for the rear flange, along with anti-vibration Vibra-tite, and a twelve-point socket for installation.
With everything sorted out we got the Bullitt Mustang up on the lift and had time to look over all the suspension upgrades that we had installed prior. Everything was still in excellent shape and tight as it should be. I was using a friend’s shop and he had not had an opportunity to see this project car so we went stem to stern going over all the parts and improvements that made the Bullitt the sweet handling car it had become.
Then we got down to the project at hand first unbolting the drive shaft at the transmission flange. Four twelve-point bolts hold it on and we used a battery powered half-inch drive impact gun to loosen up the bolts. A large screw driver was inserted in the rear U-joint to ensure the torque from the impact wrench wouldn’t spin the shaft assembly. The transmission flange actually has eight threaded holes so the four that were originally used to bolt to were marked so that they would be re-used when the new driveshaft went in.
Then we did the same at the rear flange that had six six-point bolts to remove. After that we zipped out the two bolts holding the carrier bearing assembly to the driveshaft tunnel, easing the center of the shaft down onto the exhaust for support while we finished removing the front bolts.
At this point the driveshaft was completely free and could be slide to the rear between the exhaust pipes and removed. It is always surprising just how heavy a driveshaft assembly is. The new shaft being made from aluminum tubing and minus a carrier bearing was considerably lighter
Even without the benefit of a flexible center the Shaftmasters driveshaft went in easily the same way the stock shaft had been removed. The front flange was bolted up using the original bolts and Vibra-tite from the kit was applied on their threads prior to bolting them up. They were snug, but not tight. We would save that final step for after the rear flange was bolted together.
We stretched the joint so that the rear flanges would meet enough for us to get the two bolts snugged up. Then we applied Vibra-tite to the other four bolts supplied in the kit and bolted them up to the rear. The two bolts we first put in were removed and had their threads coated with Vibra-tite as well before they went back in.
The rear bolts were also torqued, but there was not sufficient room to get a socket and torque wrench in place so we used a twelve-point box wrench and brought the torque up as evenly as we could using another wrench on the end to add torque.
We then boxed up the old driveshaft and fasteners and took the Mustang out for a test drive. I was impressed with the lack of vibration and almost complete elimination of drive line clunk.
The Bullitt’s owner remarked that “Thanks again for installing the driveshaft. It’s about 80% quieter than it was, still knocks a little in 1st or 2nd shift but I can live with that for now. I’ll eventually chase it out of there one way or another. The car seems a bit smoother, not as much harshness, seems smoother.”
So there you have it, a very effective change and improvement to a really enjoyable Mustang.