Gear Swap: 3.27's to 3.73's

Dan95-5.0

Active Member
Jun 14, 2003
1,110
0
36
Manitoba, Canada
I'm going to get some 3.73's soon to replace my 3.27's to wake up my AODE. i'm curious to how much of an improvement i will get over the factory 3.27's? Also what speedo gear do i use? i have the factory 16 inch rims but with 245's. I will be getting the FMS gears because i can get a good deal from my work. what else should i need when i get this swap done?

thanks
 
The gear swap was probably the best mod that I have done. I went with the 3:73's as well. I really wish I would have gone with the 4:10's. As for the speedo gear I am not sure. I think I used a 23 teeth one but I have 17's. I don't think the wheel sizes makes a difference.
 
my car came stock with the 327's as well and then i put in the 373's . i noticed a world of difference with the 373's, but i kinda wish that i went with 410's as well to get that little extra umph out of the hole. other than that im completely happy with them.
 
Dont waste your money on those rebuild kits, they aren't worth it. The gears should come with a pinion shim, pinion nut and crush collar, get a bottle of friction modifier for the posi, a pinion seal and pinion bearing. The 23 tooth speedo gear will get you close, but to get the car dead on, your going to need a 21 tooth speedo gear and a yellow 7 tooth (fox body) trans gear.

Joe
 
the tire size dosnt matter when you change gears and getting the speed gear, as long as the speed gear si the correct ones for that gears size. the fms catalog and the mustang unlimted catalog have charts to get the correct speedo gear
 
thanks for the help.

i plan on a adding a blower in the far future so i'd rather just buy gears just once.

Joes95GT- thanks for giving me a list of what to get and not to get. that really sumed it up for me.

Quick95GT- thats why i'm not to sure about either 3.73's or 4.10's. i'm worried if the 3.73's aren't going to be enough. but seeing how i plan on getting a blower 3.73's would be the better choice of the 2.

i guesse i'll order the gears this week then

theres a guy in the corral classifieds selling new gear sets. heres a link
http://www.corral.net/forums/showthread.php?s=&threadid=434807
 
Dan95-5.0 said:
Joes95GT- thanks for giving me a list of what to get and not to get. that really sumed it up for me.

Quick95GT- thats why i'm not to sure about either 3.73's or 4.10's. i'm worried if the 3.73's aren't going to be enough. but seeing how i plan on getting a blower 3.73's would be the better choice of the 2.
Your welcome. Another thing, if you plan on getting blown, I would not go with 4.10's for many reasons. First, without a chip, you will nail the limiter in 1st gear, and that can get ugly if done too many times. Secondly, if you plan on drag racing the car, your going to need to buy 28 inch tires because you will find that you need overdrive with a 4.10 and a 26 inch tire. 4.10's are a great gear for an N/A car, but for a blown car a 3.73 is the way to go. A 4.10 and a 28 inch tire will perform the same (close enough) as a 3.73 and a 26 inch tire. Sure, you will get more performance from the 4.10 in N/A form, but to me, it's just not worth it.

Joe
 
Joes95GT said:
Your welcome. Another thing, if you plan on getting blown, I would not go with 4.10's for many reasons. First, without a chip, you will nail the limiter in 1st gear, and that can get ugly if done too many times. Secondly, if you plan on drag racing the car, your going to need to buy 28 inch tires because you will find that you need overdrive with a 4.10 and a 26 inch tire. 4.10's are a great gear for an N/A car, but for a blown car a 3.73 is the way to go. A 4.10 and a 28 inch tire will perform the same (close enough) as a 3.73 and a 26 inch tire. Sure, you will get more performance from the 4.10 in N/A form, but to me, it's just not worth it.

Joe

Exactly what he said. You will hate the 4:10's with the blower. I have seen 4.6's get away with it but with a 5.0 it will be taxing your engine too much. 3:73's is definitely the best choice with the blower. I wouldn't go as high as 3.55's you will be disappointed.
 
If you want your speedo as close as you can get it... here is what you do to calculate. . .it is not all about "just get the 21 tooth, just get the 23 tooth" ---negative. Lets take my car for example. I HAD 4.10s in the rear end and that was too steep for the stock speedo drive gear. So i pulled the tranny, cracked the tailshaft housing off, and put a black 6 tooth drive gear. You take the # of drive gear teeth x gear ratio x # of revs per mile(rear wheels) divided by 1000 and that is the # of teeth needed on your driven gear. Mine was 6 x 4.1 x 805(which were275/40) / 1000 = 19.803a 20 tooth was the closest i got. Now that i have 3.73s it is 18.0159.... so an 18 tooth is pretty close for me. Hope this helps ya out.