North American Turbocoupe Organization

3.90 Gears...
Kuch Offline
Senior Member
So my 88 has the stock 3.55's in it, I come from the old school thought that a steeper gear helps, especially in a heavy TC and a lower torque 2.3. I know the 3.73's are kinda common in the auto TC's, but doesn't seem like much of an advantage over the 3.55's. 4.10's almost seem too much on the street, so how about some 3.90's in the 8.8? My 64 Galaxie runs 3.89's on the street and seem about perfect. According to Summit, there are 3 brands, ranging from $199 to $248 for a set of basic gears. Has anyone tried these at all? Thoughts?
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4, ported E6, 255LPH, Kirban, Stinger Exhaust, MGW shifter, K&N, Gillis valve, BP1.5, PIMPx, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low

Jeff K Offline
A 3.90 will render the already high ratio 1st gear nearly useless. Stock PCM goes into open loop over 3000 RPM, so cruising at over 65 MPH or so will put you in open loop = significant MPG reduction.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized

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