I have a 1979 f100 with a 1989 mustang 5.0 ho auto with 275/60/50 tires... Wat will be best gear ratio for speed???

 

I assume you mean 275/60-15.

Over what distance? An eighth-mile or quarter-mile? Or freeway cruising?
What tranny does it have? AOD or C4?
What is the target RPM?

 

What he said ^. What are you going to do with it? "For speed" is a broad term. Speed off the line? Speed cruising 80 down the freeway? Speed going for the the fastest land speed record on the salt flats?

 

I want to be able to cruise and still be able to be pretty quick like in a quarter mile like some thing in the middle.....

The tranny is aod and um not to sure about the rpms...

I was told that 410 gears will make the truck faster.....

 

An AOD, if I recall correctly, has a 0.67 overdrive. Pair that with a 4.10 rear gear and it'll have a 2.75 rear gear which is really good for freeway driving. Theoretically, it'll have a high top speed but it'll have to have enough HP to push a Dent with the aero of a barn door more than 120 mph.

Moving on....an AOD first gear is like 2.40. With a 4.10 rear gear, that gives ya 9.85 multiplier which is decent, but not exactly a rocketship although it will help launch out of the box quicker than with a numerically lower rear gear. A better first gear ratio is in the 13s... like a 3.27 first gear and a 4.10 rear rear which equates to 13.4. That's on par with the latest muscle.

Be mindful with a 2.4 and 4.10 cuz stock AODs weren't exactly known for launching a 4,000-4,500 lb behemoth off the line.

 

Wat gears would u reccomend for me to wrk.the best with my truck?????

 

Simply put, 4.10's with an overdrive, or 3.50's without an overdrive, would get you down the road. I say 3.50's because they are very common. They make a 3.73 gear for the 9", but you'll more than likely have to build it yourself or find someone that's already done it.

 

Concur with 4.10 rear gears... just be mindful that you've got a passenger car-based AOD... not a 5.4L truck-sourced 4R70W which, acccording to Ford in 2003, can handle more than 500 ft.lbs of torque.

 

My brother know about putting in the gears so I dont have to wrry about that I was was also looking into 3.75 and 3.90 gears would u guys still reccomend the 4.10?????

 

Do the math... Engine RPM Calculator

A 0.67 fourth gear and a 3.90 rear gear results in a final drive ratio of 2.61. A 275/60-15 is about 28 inches tall. At 70 mph, that's right at 2200 RPM and 80 mph it is 2500 RPM.

I would consider a 3.90 if the highways around me are on the flatlands. If you've got rolling hills, ya might be dropping into third alot to maintain your desired speed.

Ya need to factor in your engine's RPM sweet spot... too low and it'll be a dawg... if on the border, then it'll be frequently shifting in and out of 4th.