Stock TTB coils sit at roughly 377 lb/in without A/C and 430 lb/in with A/C — replace them with a matched pair, not one side at a time, and budget 2-4 hours per truck with a rental internal spring compressor.
Front coils on a TTB Bronco II carry the truck and absorb the secondary impacts that the TTB beam doesn't handle in its pivot. When they sag — and after 30+ years, they sag — the truck sits low, eats bump stops over speed bumps, and rides like a buckboard because the dampers are working past their intended stroke. The fix is a fresh pair of coils. Don't replace one side. Springs settle as a pair, and a mismatched set will pull the truck and put uneven load on the radius arms.
Buying springs means deciding ride height first. Stock-replacement coils restore factory height — around 377 lb/in rate, no A/C — and feel like the truck did when it was new. A 2 to 2.5 inch lift pair (Skyjacker FC25, Duff, or Rough Country) sits the truck higher, runs a stiffer rate, and clears 31x10.50 tires with a small trim. Going beyond 3 inches with coils alone is a fight: the TTB beam rotates downward, camber goes negative, and you need cut-and-turn beam work plus an adjustable alignment bushing to keep the front geometry honest. For a daily-driven Bronco II, 2.5 inches is the sweet spot.
The actual replacement is straightforward but requires one specialty tool: an internal coil spring compressor that fits through the bottom of the spring perch. Auto parts stores rent them for free with a deposit. Don't try to swap TTB coils with external clamshell compressors — the geometry doesn't allow safe purchase on the coil.
Lift the front, support the frame on stands behind the radius arms, and remove the front wheels. Disconnect the lower shock mount and let the axle droop. Disconnect the sway bar end link on the side you're working on. Pop the brake hose bracket off the frame so it doesn't pull. Compress the coil with the internal tool, then jack the axle down until the spring is free to come out. With the spring out, inspect the upper isolator pad — replace it if cracked or hardened. Install the new spring, slowly release the compressor, and reconnect the shock and sway bar. Repeat on the other side.
| Part | Vendor | Est. price |
|---|---|---|
| Stock-height replacement coils — pair (Moog 81067) | Rock Auto / NAPA | ~$140 |
| Skyjacker 2.5-inch lift coils — pair | Summit Racing / 4WP | ~$220 |
| James Duff 2-inch lift coils — pair | James Duff Inc. | ~$230 |
| Spring isolator pad — upper | Rock Auto | ~$14 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.