Transmission Upgrade, Miles per Gallon, and Future Plans

[bretamo]

I have committed to installing a quality turbo kit next year, which will allow my stock-like set up to maximize street performance and miles-per-gallon. With the stock CAM I look to have a daily driver that has decent gas mileage, but can get a boost to 450hp when I need it.

That given, I am wondering if the T-56 6-speed transmission would be a good addition.

I drive about 100 miles a day, with about half of that on the hghway either in 4th gear (45-55mph) or in 5th (65-75mph).

The T-56 has gear ratios of 2.97 2.07 1.43 1.00 .80 .62, and I am curious about that ".80" 5th gear. I am wondering if the T-56's 5th gear would give me a bit of a break on gas mileage when I steadily drive in that 45-55mph range?

I do have some concerns. What would the T-56 do to my stop-light-to-stop light driving (the 2.97 gear 1st gear), and will my speedometer be accurate?

I'd appreciate a comment or two from anyone who installed the T-56 in their near stock-like Mustang.

Thanks in advance.

 

[Mustang5L5]

A set of steep gears will cure that low 1st gear. Use some 3.73's or 4.10's and you won't have a problem but you will need to use 6th to keep a low OD. Then again you may have the HP levels needed to push the t-56. A lot of guys who have issues with the steep gearing don't have the 400HP/400TQ that the trans was geared around.

I don't know about gas milage though. Honestly a 450HP 5.0 Mustang isn't exactly going to sip gas. A lot of claims of good mileage (~25MPG) come from guys who do strictly highway driving in the highest gear...which sounds like your situation. Once they get around town and start shifting it goes right down to nothing.