sound off 3.55's or 3.73's

[Snikt89GT]

You might try checking your rpm again. 3-400 rpm difference is pretty steep between an actual 70mph and 80mph.

What year tranny do you have? Correct speedo gears? You sure you have stock 3.08:1's? You don't think they could have been changed?

Speedo accurate? Tach accurate?

I'll check it again the next time I drive, i'm positive it was 2,500RPM at 80MPH though. I checked the speedo with a friend on the phone and it's accurate, don't know how to check if my tach is accurate?

The previous owner said they were the stock 3.08s and it doesn't look like they have been changed.

I have an 89 1/2 - 93 T5 tranny with 8T driven gear

 

[5spd GT]

Cool, those rpms sound closer to a 3.55 or 3.27 gear ratio.

Do you have the right speedo gear in it?

 

[Black1987Stang]

Howdy, What kind of TKO? 5th gear ratio? What size tires? XXX/XX/XX? Let me know...and I'll do the math for you

I got a problem for u 5spd....I got 26 inch tires, (255-50-16) 373s im pretty positive, and a t-5, last 3 digits is 169 which is 87-89 year...my tranny came out of another stang.....if u do the calculations in 4th gear I do have 373 gears...BUT if u do the calculations with the 5th gear (.68) from that year tranny and the speed/rpms im going i should be at 2450 rpms (5th gear) give or take...but instead im at 3,000rpms instead...I kept trying different ratios to put in as the 5th gear and says it would be a .82 5th to be at 3,000rpms ....when i put it in overdrive from 4th it drops 400-500 rpms does that seem normal? cuz it seems like it should lug down alot more into 5th but it doesnt.....at 2,000rpms in 4th gear im at 43mph and when i put it in 5th at 2,000rpms im at 54mph figure that one out, from everyone else im seeing they gain around 20mph from 4th to 5th shift at a given rpm where i only gain like 10mph.....btw i have a red speedo gear

 

[PjctWhiteNotch]

go with the 3.73 you won't be disapointed
or the 3.55 route for some highway use, but my car has a 3.73 and its fine on the highway. i spell like shi* so bare wit me.

 

[90_Red_LX]

I guess I'm about the only one who seen little difference with 3.55s over 3.73s so stuck in the steeper gear. 200 rpm would make no difference at 60mph to me, hell 2500rpm would be fine with me, but 4.10 would be too steep for traction. The only major difference I would see between 3.55s and 3.73 is if you were running out of gear just before the traps, or needed a little more gear to get through the traps better.

 

[onefstsnake]

3.73's

I turn about 2700rpm at 70mph
But didnt the 93 WC T5's have a different ratio in the tranny?

 

[Snikt89GT]

3.73's

I turn about 2700rpm at 70mph
But didnt the 93 WC T5's have a different ratio in the tranny?

Late 89 - 93 had the same tranny (300 ft lb capacity vs 265). All of 85-93 though had the same .675 5th gear ratio

 

[onefstsnake]

Late 89 - 93 had the same tranny (300 ft lb capacity vs 265). All of 85-93 though had the same .675 5th gear ratio

hmm wonder why mine is almost 500rpm off. Im not reading off the stock tach.

Tires are 26" and definately 3.73's

 

[onefstsnake]

double post

 

[stangjunkie]

i would say to go with 3.55 thats what i did... granted i do alot of highway driving even so its a great all around gear.

i skipped over the post about people arguing however things to consider..... i swapped my speedo gear to the proper one orated to me in concensus by stangnet guys and ford guys, when i was showing 55mph i passed a radar that clocked me at 50mph...

also stock tach's have quite a bit of innacuracy... so maybe a few hundred rpm here and there not so important if you are on a stock tach

if this has been said or doesn't matter just ignore me

 

[89white50]

with my 327's 70mph is 2200...maybe i have a 4 banger t-5, but my car was completely stock, and everything i've changed so far has been original so i cant see why it would be.

 

[90]

honestly i know im new here, but i can put down 5th gear, 69-74 mph (my speed-o is off about 8mph) at exactly 2k.. with 3:73... if i hold 2k its vary quite, if i go over its loud and under starts a bog like sound.. with 17" street slicks / 5lug swap (dont know if that matters ?)

 

[Black Sun 5.0]

Semi-hijack here: What is preferred for a supercharged
5-speed? 3.55 vs. 3.73?

 

[srothfuss]

depends on the SC and the total setup of the car but in general.

Roots/Twin Screw = 3.55's or lower

Centrifugal = 3.73's

 

[Black Sun 5.0]

OK. I already have heads, cam, intake, exhaust, pretty much all the general bolt on's. I think I'll be going with the SC-Trim.