A green 1973 88-inch Series III gone through end to end: a Forbyn Bros billet spindle and disc brake conversion kit, a booster and vacuum pump, a new high-output gearbox and clutch, and long-travel suspension.
This green 1973 Series III, a right-hand-drive 88-inch diesel, spent the summer of 2022 in my shop, June into August. It came over from England, where it had spent decades working a field, and Series trucks are simple enough that they punish half-done work. So I went through it one system at a time instead of chasing symptoms.
It started at the corners. The original cast iron spindles were fifty years old and had been abused for most of them, so they came out and the Forbyn Bros billet spindle and four-wheel disc brake conversion went in. Forbyn Bros sells it as a complete kit: billet spindle housings, hubs, rotors, and calipers. Every piece got laid out on the bench and checked before any of it went on the truck. It put the spindles and front-end geometry back to new and replaced the drums with discs on all four wheels. To go with it I installed a brake booster and pedal assembly, and because this engine does not make enough vacuum at idle to run a booster on its own, an electric vacuum pump feeds it. New hydraulic lines and hoses went in all the way around.
The driveline got the same treatment. The original gearbox came out and apart for inspection, and a new high-output gearbox went in with a new shifter, a new clutch, a new slave cylinder, and new hydraulic lines. Both swivel housings were rebuilt, both diffs were resealed, and manual locking hubs went on up front with new hub bearings. Long-travel suspension went under it: parabolic springs and long-travel shocks at all four corners, with new shackles, bushings, and heavy-duty steering rods.
Under the hood I cleaned up the engine bay wiring and battery cables, repaired the battery box and made a proper hold-down, sorted the hazard and lighting circuit, flushed the diesel tank, ran new fuel lines, replaced the mounts, and fitted a full exhaust with the downpipe modified to clear the intake. It went back down on powder-coated wheels and all-terrain tires, got an alignment, and the last step was a real test drive. It still looks like a Series III. It just stops, steers, and shifts like one that was put together right.
Before the new unit went in, the original gearbox and transfer case came out and went all the way down to the gear stacks, with the case pieces laid out, so every gear and its teeth could be inspected instead of guessed at. Those teardown photos are in the gallery below.
How it came in, stock and tired, before the brakes, gearbox, wiring, and suspension work.
