Performance Transmission Comparison Test - C4 vs. Five-Speed
| Tech Specs - Test Car at a Glance | | Car | '84Mustang: Project Pro Tree Mustang | | Engine | OEM '91 5.0 H.O. short-block | | Cylinder Heads | '71 351W, 1.90 intake, 1.60 exhaust | | Camshaft | FRPP X-303 | | Carb | Carb Shop 750 Holley | | Intake | Weiand Stealth, port-matched, with 1-in four-hole spacer | | Timing | 40 deg total | | Exhaust | Equal-length shorties, 2.5-in H-pipe, Flowmaster three-chamber mufflers | | Rear | Dana 44 with Detroit Locker | | Gears | 4.27 Precision Gear | | Suspension (front) | Koni adjustable struts and four-cylinder coils | | Suspension (rear) | Koni adjustable shocks, Moroso Trick springs, Steeda aluminum lower control arms, FRPP upper arms, airbag | | Lubricants | Amsoil 10W-30, engine; Castrol Type F, C4; Redline Lightweight Shockproof, Tremec; Amsoil 75W-90 gear lube,rear | | Tires | P165 radials, front; M/T 26x10, rear |
On-Track Comparison: C4 vs. Five-Speed | C4 | | Date | 60 FT | 330 FT | 660 FT | 1,000 FT | ET/MPH | Comments | | | 6/28 | 1.596 | 4.840 | 7.648 | 10.112 | 12.214 /107.22 | Shift 6,000, 90 deg, 56%. 29.93, 2,400 ft. Engine 150 deg | | 1.602 | 4.830 | 7.630 | 10.085 | 12.179/107.62 | Shift 6,200, 86 deg, 63%, 29.92, 2,207 ft. Bogged. Liked higher shift point. Air change should equal 12.20. | | 1.602 | 4.847 | 7.648 | 10.102 | 12.195/107.69 | Shift 6,200, 86 deg, 63%, 29.92, 2,200 ft. 11.75 psi in slicks | | 1.592 | 4.829 | 7.626 | 10.078 | 12.167/107.86 | Shift 6,200, 83 deg, 68%, 29.93, 2,054 ft. 12 psi in slicks | | 6/30 | 1.578 | 4.792 | 7.578 | 10.024 | 12.109/108.00 | Shift 6,200, 80 deg, 47%, 29.96, 1,550 ft, 150 deg. Air change should equal 12.137 from last pass on 6/28. | | 1.588 | 4.808 | 7.590 | 10.026 | 12.099/108.68 | Shift 6,200, 77 deg, 45%, 29.98, 1,300 ft. Air change should equal 12.093. | | 7/7 | 1.595 | 4.811 | 7.602 | 10.048 | 12.129/108.35 | Shift 6,200, 74 deg, 69%, 30.14, 1,300. Higher humidity hurts, increased barometer seems to help offset e.t. loss | | 1.599 | 4.819, | 7.607 | 10.050 | 12.128/108.45 | Shift 6,200, 72 deg, 75%, 30.15, 1,000 ft. Air change should equal 12.108 | - All tests with C4 were with 4,700-rpm transbrake launch, 11.5 psi in slicks, 25 psi in airbag. Engine at 40 degrees timing, 85 Max Jet, 160 degrees water temp. Car weight 3,030 lbs, with approx. 47% on rear tires. Struts and shocks full loose.
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The first outing with the stick exposed a serious problem with our rear lower control arm bushings (right). The resulting axle movement broke a rear shock a split second before the 1-2 shift, yet it produced the quickest pass of the night. New bushings (left) and fresh adjustable shocks cured the problem. | 
Project PTM launches hard from the Raceway Park starting line. The stick was a little quicker and provided more fun, while the auto was consistent and just the ticket for weekly bracket racing. | 
The engine is a 302 using a stock roller block and old-school 351 heads. It makes just over 300 hp at the wheels and can propel our Mustang into the 11s. |
| Tremec Five-Speed | | Date | 60 FT | 330 FT | 660 FT | 1,000 FT | ET/MPH | Comments | | | 8/11 | 1.547 | 4.837 | 7.583 | 9.969 | 11.991/111.55 | Shift 6,200, 84 deg, 34%, 29.84, 2,000 ft. Nose bouncing on launch | | 1.542 | 4.843 | 7.598 | 9.987 | 12.015/111.25 | Launch 5,500, Shift 6,200, 80 deg, 47%, 29.84, 1,750 ft. Air should equal 11.975. No change in 60 ft. | | | 1.567 | 4.800 | 7.535 | 9.908 | 11.926/111.69 | | - Launch 4,700, shift 6,000, 68 degrees temp, 70% humidity, 29.88 barometer, 1,000-foot corrected altitude. Air should equal 11.924. Broke rear shock.
- Used same 4,700-rpm launch, 11.5 psi, 25 psi airbag (too much body roll). Engine 40 degrees timing, 85 Max Jet, 160 degrees water temp. Car weight 3,050 lbs, with 48.5% on rear tires. Koni struts one turn tight, shocks full tight.
- Video showed nose bounced on launch and 1-2 shift. Left rear shock broke prior to 1-2 shift on last pass.
| | 8/23 | 1.577 | 4.810 | 7.535 | 9.910 | 11.930/111.65 | Launch 4,700, Shift 6,000, 92 deg, 32%, 29.85, 2,390 ft. Air change should equal 12.019 from last pass on 8/11 | | 1.560 | 4.799 | 7.519 | 9.880 | 11.889/112.21 | Launch 5,500, Shift 6,200, 87 deg 40%, 29.85, 2,100 ft. Air change should equal 11.910 from previous pass | | 1.578 | 4.809 | 7.559 | 9.936 | 11.953/111.94 | Launch 6,000, Shift 6,200, 81 deg, 45%, 29.85, 1,679 ft. Spun bad. Air change should equal 11.861 | | 1.558 | 4.760 | 7.497 | 9.883 | 11.908/111.45 | Launch 55, Shift 62, 73 deg, 53%, 29.89, 1,267 ft. Spun, but pulled wheels. Shift light broke. Air should equal 11.834 | - Replaced damaged LCA bushings, installed new Strange adjustable shocks. Car weight 3,056 lbs. Rear tires at 12 psi
- Airbag now 30 psi (body roll eliminated), Koni struts 1.5 turns tight, Strange shocks on Pos. 6 (out of possible 8). No changes to engine
- Shift light broke on last run, no signal for Third or Fourth gear shift. Overshifted by unknown amount
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| Conclusions | - The five-speed is quicker using the identical launch and shift rpm, but how much?
- At 2,000 feet, the five-speed is 0.176 second and nearly 4 mph better, including 0.05 quicker in the 60-foot; all with destroyed LCA bushings
- With repaired bushings and new shocks, and better suspension tuning for stick launches-at 2,400 feet-improvement was 0.284 second and 4.5 mph over the C4.
- All this was accomplished with 20-30 lbs additional weight.
- The car now runs the same e.t. at 2,400 feet elevation that it ran with the C4 at 600 feet below sea level.
- The potential for the five-speed is 11.70s in better air.
- With traction and suspension tuning, further gains are possible.
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