Vintage Mustang Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
143 Posts
Discussion Starter #1
I have a 66 stang and am dropping in an 8" rear. It is an I6 but is being tricked out a bit with the aussie head, new holley carb, headers, etc. It should put out around 200+ horses. I was wondering if I should go as low as 3.80 gears. I originally thought 3.55 would be ideal but have heard others saying that 3.80 would be ideal. I don't plan on doing very much highway driving but I will be doing some. Also, the unit I am looking at is Posi and I was wondering if this will get you a but more go off the line as well? Will the added traction make any difference in pickup?

Thanks

Tim
 

·
Registered
Joined
·
759 Posts
I'm currently installing a 3:00 traction-loc as I wanted the car to be friendly in the highway. 60 MPH will be about 2600 RPM with automatic, 3:25 @ 60MPH will be around 3300 RPM. All this is also affected by your final drive in tranny.
 

·
Moderator
Joined
·
7,010 Posts
Having the limited slip rear will help you off the line if traction is a problem. With the stright 6 it might or might not be an issue. The 6's do have a lot of torque...so I'm guessing it will help.

Regarding the gear ratio...I have 3.55s. Personnally, I wouldn't even want 3.55's if I didn't have overdrive. I'd go with 3.25's. You don't want 3.80's.

Phil
 

·
Registered
Joined
·
201 Posts
I have 3.80 and there is no way I would consider using it for any type of highway driving unless I was to switch over to an AOD tranny.
 

·
Registered
Joined
·
143 Posts
Discussion Starter #5
Well I guess I should have mentioned that I am installing a T5 tranny from an 87 mustang with overdrive.
 

·
Registered
Joined
·
1,963 Posts
I just returned from a nearly 6000 mile road trip with 3.50's on a 3-spd stick (1:1 in top), and I can tell you it's very liveable. We cruised at 70-75 mph all day. With an O.D. top, I'd go even lower. That is, 3:80's would be no problem. Now whether 3:80's would make your first gear a useless granny gear, I don't know.

Posi will not cut your E.T.'s with a 200 hp six. It will avoid embarassing one-wheel burnouts, though.

One other thing that I have discovered is that traction bars are a necessity if you want to do any clutch dumps. I had to break a spring mount off the axle housing to find that out. ::

7
 

·
Registered
Joined
·
10,287 Posts
Ernie, I have 3.25 gears and by math and tach it turns about 2650 @ 60mph
 

·
Registered
Joined
·
2,614 Posts
if your going to be running a T5, i think you can get away with the 3.80's if you dont mind spinning some rpm on the freeway.

i'l tell you though, i run 3.55's with my c4, and i HATE it on the freeway, i avoid it with a passion. especially seeing as how here in the bay area if your going 75 your getting run off the road !
 

·
Registered
Joined
·
7,295 Posts
I just installed a set of 3.80's this weekend with my C4. but I am also running a 3000 rpm stall and need to keep the rpm's up while on the highway. I have a set of 2.70's i just yanked out of the 8"-er iy ya want those!! ::
 
1 - 10 of 10 Posts
Top