Disadvantages of having a lower 5th gear?

[BlownStangGT]

I would like to know if there are any type of disadvatages of having a lower 5th gear. I got my new 5.0 mustang mag and I read all about the new tremmecs, they come with an optional .64 5th gear. Well, I have been limping my t-5 since November and I am tired of rebuilding them since this will be my 5th t-5 rebuilt in 5 years (some were under warrenty) I am going to go ahead and save for a tremmec. Anyways, I will have 3.73s gears in my car and would love to get the cruise rpms down to like 2,000 at like 70-75 with the 3.73s. So if someone made a tremmec with a deeper 5th what would be the disadvantages? Im coming from 2.73s right now and I love cruising hte highway at 2k or less rpms. But I hate how doggy they are around the street. So please fill me in

 

[Grn92LX]

The lower 5th geared tremec also has a lower first gear. Keep that in mind. And with 273's you dont need a lower 5th gear. You'll be around 2500rpm cruise at about 70-75 with 373's and the stock .68 ratio 5th. Would you rather have more pull or cuise lower on the hwy? I'd prefer more pull over 200rpm less crusing rpm. I believe its a 2.87 first vs a 3.27 first in the tremec 500 and 600

 

[85_SS_302_Coupe]

I'd love to have a custom trany with a low 5th for gas mileage, and the first 4 gears for racing.

 

[Michael Yount]

My car has the World Class T-5Z from Ford Racing, according to their catalog, and my calculations, it has the .625 ratio 5th gear. It is a long gap from 4th to 5th, but it does make highway cruising tolerable. My car has shorter tires than a Stang, so with 3.73's it's like a Stang with 3.90's. At 65 mph, I'm around 23-2400 rpm. 23-25 mpg. My combo is built for lots of torque down low - so it doesn't mind the gear at all. Yours seems basically stock, so it should be fine with that 5th gear.

By the way the correct terminology when going from a .68 to .63 would be to call it a "higher" gear, not lower. Higher means lower numerically; a "lower" gear means higher numerically.

 

[85_SS_302_Coupe]

Yea what Michael said...lol

I was thinking today that i got that mixed up.