Which is BEST & Difference Between 3.55s & 3.73s

[chrismc101]

I got an '86 GT 5.0 and gears is one thing that I will in the near future replace. Just in reading 5.0 and Mustang magazines, I see sum perfer 3.55 and sum perfer 3.73.

There may be times where I go to Piedmont track which is about 1 hour 20 minutes away, but that won't be everyday driving. My daily commute to work is only 20 minutes. So, she will be a in town, street runner. Of course I wanna keep gas mileage in mind, but I wanna quick performance. Correct me if I'm wrong, but changing gear won't gain or loose in HPs.

So tell me everybody, which is the best gear for me to get in my 86?

[Gearhead999]

Since you have a 5 speed with O/D, I would opt for the 3.73 gear. It will be slightly stronger from a standing start.

[Ieatcamaros]

Do a search in this forum for 3.73 gears. This topic has been brought up a million times. There are so many different opinions out there. IMO, I like the pull of 3.73's over the 3.55's. It's not a whole lot of difference, but just enough to tell. The gas mileage difference is slim. If you have an auto, I'd say put in at least 4.10 gears. The reason is because the aod has a 2.40 1st gear and you need all the help you can get out of the hole. I have a t5 and I went from 2.73's to 4.10's. The difference as far as cruising would be like losing 5th gear on the highway. So if you have a stick car, then drive down the highway in 4th gear at normal speed and see if you can stand the rpms. Putting in 3.73's would be like cutting about 2-300 rpms off the cruising rpm with 4.10's. Putting in 3.55's would cut about another 100 rpms off. So you see that there is not much difference on the top end. To hardcore racers those few rpms can make a huge difference by the time you get to the finish line. That is why the ratios are so close together. It is the low end that makes all the difference. With an aod and 2.73's your final drive ratio is 6.55. With 4.10's the final drive goes up to 9.84. Make sense?