F100 Driveshaft Transformed into Mustang Custom Build
The video shows converting an old 1981 F100 driveshaft into a custom-length driveshaft for a 1965 Ford Mustang. The build involves shortening and trimming the donor shaft, swapping/installing U-joints and a flange/yoke, welding and finishing, then balancing and installing the finished shaft.
Build Sequence
1. Remove and inspect donor driveshaft
Take the F100 driveshaft off the donor vehicle (or from storage). Inspect tube, splines, yokes and U-joints for wear and damage; decide which components will be reused.
2. Measure required finished length
Measure the Mustang pinion-to-transmission flange distance with the suspension at ride height and determine the required driveshaft center-to-center or overall length. Account for slip and travel.
3. Cut and prep the donor tube
Mark and cut the donor tube to the measured length using a chop saw or cutoff wheel. Square and clean up the cut ends for welding; prep mating surfaces by removing paint and rust.
4. Fit and tack-weld yoke/flange
Fit the driveshaft yoke or weld-on flange to the prepared tube. Tack-weld in multiple places to maintain alignment and check concentricity and fitment to the vehicle flanges or U-joint.
5. Final weld and heat control
Complete full welds around the joint in short passes to avoid warping. Allow cooling between passes and grind smooth if needed while keeping the tube balanced and straight.
6. Install U-joints and hardware
Press in new or serviced U-joint caps, install snap rings or retaining hardware, and torque flange bolts to spec. Grease U-joints if serviceable.
7. Balance the driveshaft
Take the completed driveshaft to a shop for dynamic balancing or use a driveshaft balancing setup. Add balancing weights as required to remove vibration.
8. Finish, paint and reinstall
Apply rust inhibitor or paint to the shaft, install the driveshaft onto the Mustang with proper bolts and torque, check for driveline angle and test drive for vibration.
Frequently Asked Questions
Is welding on the driveshaft safe?
Welding is common for custom driveshaft work when done correctly. Use proper welding technique, avoid overheating (which can warp the tube), ensure concentric alignment, and have the shaft balanced afterwards. If unsure, have a professional perform or inspect the work.
VIEW FULL ARTICLE →Can I use an F100 driveshaft in my '65 Mustang?
Yes, a donor F100 driveshaft can be repurposed if shortened and refitted with the correct yoke/flange and U-joints. You must verify spline/yoke compatibility or use a welded flange to match the Mustang pinion or transmission flange.
VIEW FULL ARTICLE →How do I determine the correct driveshaft length?
Measure center-to-center or slip-yoke engagement distance on the vehicle at ride height with the suspension sagged. Allow safe slip travel (usually 1–2 inches) to avoid bottoming out under suspension movement.
VIEW FULL ARTICLE →What size U-joints do I need?
You need U-joints that match the yoke dimensions used on the modified shaft and the vehicle's companion flange. The video recommends measuring the yoke width and bearing cap diameter and sourcing the correct U-joint size (commonly 1310 or 1350 sizes on classic Fords), but verify before purchase.
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Parts Used (7)
Two U-joints (inboard and outboard) or a 4-cap replacement set; size must match yokes (confirm 1310/1350 as required).
Flange or replacement yoke welded to the shortened tube to match the Mustang pinion/shaft or transmission flange.
Appropriate filler for shaft material (mild steel rod/wire) used to weld flange/yoke to tube.
Bolts for flange, snap rings or retaining hardware and grease for U-joints.