Hey guys! I have a 2003 Mustang GT and was wondering if I could get some input on gear changes. The car has a TKO600 (.82 in 5th) with 4.10's in the back right now. First gear is way too short. Was wondering what gears you guys would suggest I throw in the back! Thanks
A 0.82:1 overdrive suggests the TKO is either a TCET4617 or TCET4618, both of which have a 2.87:1 1st gear ratio. This is actually fairly tall. A TR3650 has a 3.38:1 1st gear and seems to be fine with shorter rear gears.
Is that a typo in your OP? Did you mean to say that 5th gear is way too short (which is why you mentioned the 0.82:1 ratio...)?
If so, consider: A TR3650 has something like a 0.62:1 5th, which is basically 1.323x taller than the 0.82 in the TKO. If you want similar highway RPM to a TR3650 car with 4.10s you're going to need to go down to (mathematically) 3.10 (e.g. 3.27:1 or the stock ratio.) I suspect that's going to suck given the tall-ish 1st gear ratio so you're looking at either 3.55, 3.73 or 3.90. IMO, 3.73s are a decent all-round gear. A 3.73 would knock roughly 10% off your cruising RPM but still give you a decent mechanical advantage in the lower gears.