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    3/07/2015 7:16 PM  #1

    terry
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    From: vandalia, illinois
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    Final gear ratio question

    Below is a quote from Jerry from another thread.  Someone tell me the differenc in final gear ratio between the T-5 and the AOD?????

    The gear you choose should depend on how you're going to use the car.  I started with a 3.55 gear which is a  fun sport gear, but my near stock 5.0 & T5 just doesn't need the rpm. I changed to a 3.25 for those long bash trips on the interstate. For my car, it was the way to go... the 3.25 is lot more comfortable at 78mph, plus I gained 2 mpg consistently.   If you're gonna hot rod around town, the 3.55 may be a better choice.

    Last edited by terry (3/07/2015 7:16 PM)

     

    3/07/2015 7:22 PM  #2

    barnett468
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    Re: Final gear ratio question

    terry wrote:

    Below is a quote from Jerry from another thread.  Someone tell me the differenc in final gear ratio between the T-5 and the AOD?????

    most aod's are .067

     

    Last edited by barnett468 (3/07/2015 7:28 PM)

     

    3/07/2015 7:38 PM  #3

    lowercasesteve
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    Re: Final gear ratio question

    This should give you a good idea of T5 ratios.http://www.allfordmustangs.com/Detailed/349.shtml

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    3/07/2015 8:08 PM  #4

    terry
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    Re: Final gear ratio question

    I was looking after I posted this earlier.  Looks like they are pretty closley matched .67 to .68  I am still mulling over changing my 3.00 to 3.25 or 3.55 just havent decided which.

    65 with 302 HO  AOD 3.00 gears runs 1750 at 60 mph

       •Thread Starter
     

    3/08/2015 6:18 AM  #5

    TKOPerformance
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    Re: Final gear ratio question

    What size tire are you running?

     

    3/08/2015 6:39 AM  #6

    terry
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    Re: Final gear ratio question

    215/45-17

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    3/08/2015 10:09 AM  #7

    Jeff in GA
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    Re: Final gear ratio question

    I have had two different '65s, both with T5s. My first had an '85 T5 with 3.35 first and 0.68 OD with 3.50:1 in the pumpkin. My current car has the Motorsport T5 with 2.95 first and 0.63 OD with 3.25:1 gears. It is not exactly an apples apples comparison, but if I did it again I'd go with the 3.50:1. Good luck.

    1965 Mustang 2+2 EFI
     

    3/08/2015 12:30 PM  #8

    devovino
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    Re: Final gear ratio question

    terry wrote:

    I was looking after I posted this earlier.  Looks like they are pretty closley matched .67 to .68  I am still mulling over changing my 3.00 to 3.25 or 3.55 just havent decided which.

    65 with 302 HO  AOD 3.00 gears runs 1750 at 60 mph

     I think that top quote looks familiar. Either way, how do you like to aforementioned combination (3.00 w/ 302) Do you feel at 60-65, there is a lack of exceleration if you got into it?  Why are you considering re-gearing?
     

    All men die, but not all men truly ever live.
     

    3/08/2015 12:30 PM  #9

    ultrastang
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    Re: Final gear ratio question

    With an overdrive transmission in overdrive, the rear end ratio will have a lesser final drive equivalent than what its rear end ratio actually is.

    If you had a T-5 with a .68:1 overdrive gear and a rear end ratio of 3.55:1, the final drive equivalent would be as if the rear end ratio was 2.41:1. Final drive equivalent is figured by multiplying the O.D. ratio by the rear end ratio. (.68 x 3.55 = 2.41).

    If the T-5 had a .63:1 overdrive ratio, the final drive equivalent would be 2.24:1.

    In the production days of the '87-'93 5.0L Mustangs with a T-5 (3.35 1st gear), the most common stock ratio in their 8.8" rear ends was 2.73:1. There were lower (numerically higher) optional ratios available but, both my '89 and '90 5.0L GTs with a T-5 had factory 2.73 geared rear ends. Final drive equivalent on them was 1.86:1 (which was very under geared in the rear).

     

    3/08/2015 4:11 PM  #10

    terry
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    Re: Final gear ratio question

    devovino wrote:

    terry wrote:

    I was looking after I posted this earlier.  Looks like they are pretty closley matched .67 to .68  I am still mulling over changing my 3.00 to 3.25 or 3.55 just havent decided which.

    65 with 302 HO  AOD 3.00 gears runs 1750 at 60 mph

     I think that top quote looks familiar. Either way, how do you like to aforementioned combination (3.00 w/ 302) Do you feel at 60-65, there is a lack of exceleration if you got into it?  Why are you considering re-gearing?
     

    This is me thinking out loud
    I think the 3.00 with an aod actually bogs the engine down at highway speeds in OD.  I think if I bring the gear ratio down to say 3.25 or 3.55  it will run better overall.  Hoping I can bring my fuel mileage up a few mpgs.  I just think this car should get better fuel mileage than 16 mpg considering the setup. A few people I've talked to suggested  that the bogging down actually hurts performance.  

       •Thread Starter
     

    3/08/2015 4:33 PM  #11

    Brents65
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    Re: Final gear ratio question

    ultrastang wrote:

    With an overdrive transmission in overdrive, the rear end ratio will have a lesser final drive equivalent than what its rear end ratio actually is.

    If you had a T-5 with a .68:1 overdrive gear and a rear end ratio of 3.55:1, the final drive equivalent would be as if the rear end ratio was 2.41:1. Final drive equivalent is figured by multiplying the O.D. ratio by the rear end ratio. (.68 x 3.55 = 2.41).

    If the T-5 had a .63:1 overdrive ratio, the final drive equivalent would be 2.24:1.

    In the production days of the '87-'93 5.0L Mustangs with a T-5 (3.35 1st gear), the most common stock ratio in their 8.8" rear ends was 2.73:1. There were lower (numerically higher) optional ratios available but, both my '89 and '90 5.0L GTs with a T-5 had factory 2.73 geared rear ends. Final drive equivalent on them was 1.86:1 (which was very under geared in the rear).

     
    Do you mean 3.73?  I had an 89 that was a 3.73-  I thought that was the most popular ratio.

    65 mustang coupe, 351W, C6-  2800 stall, B&M blower, 9inch- trac-loc 3.70 gears
     

    3/08/2015 4:59 PM  #12

    GPatrick
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    Re: Final gear ratio question

    My 85 GT had 2.73's as well as my 93 LX 5.0.  If you were lucky you could find a 3.08 manual car.  I think a number of the automatic cars came with 3.27's.  With the small rear in the '85 (8.8" was not used until 86) I put in 3.45's and it became a fun car.

     

    3/08/2015 5:07 PM  #13

    MS
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    Re: Final gear ratio question

    Barnett, you must get really great mileage with that .068 !!!

    My T5 had 0.67:1.  Pretty sure my TKO 600 is same or maybe 0.68:1 if that is any noticeable difference.  At 70 MPH I am at 2,000 RPM with the 3.50:1 rear end and 245x45/17 tires.   Cruise is exactly same as my 2015 Mustang GT in sixth gear and it has 3.55 ratio rear end.

    I wish I was running a little higher RPM.  My old 3.70 rear gear was best overall.   If you have a stockish engine, you can run the 3.0 or 3.25.  If you have any kind of cam in it, you will be sluggishly moving down the highway at 70 MPH with a 3.50 or less.  Even my 427 with over 500 hp would run alot better at a little higher cruise RPM.

    Last edited by MustangSteve (3/08/2015 5:11 PM)

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/08/2015 5:29 PM  #14

    Tubo
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    Re: Final gear ratio question

    Terry as you never drive your 2+2 to a Bash(Noooo Vandalia don't count) going with the more performance geared 3.55 will keep you happy. Leave the 3.25's fer the guy's who do the long distance cruising, and like the 26+ mpg.

    Tubo

    If it ain't broke, I haven't modified it Yet
     

    3/08/2015 5:58 PM  #15

    terry
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    Re: Final gear ratio question

    Tubo wrote:

    Terry as you never drive your 2+2 to a Bash(Noooo Vandalia don't count) going with the more performance geared 3.55 will keep you happy. Leave the 3.25's fer the guy's who do the long distance cruising, and like the 26+ mpg.

    Tubo

    OUCH!!  that smarted just a tinge!!  I'll get even you just wait!!!

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    3/08/2015 6:34 PM  #16

    DC
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    Re: Final gear ratio question

    I agree that you need to go for smiles not miles! I only have one car with less than 3.73 and there is a gear  set laying on the bench for it which is a 3.90. I think we need 8 speed tranny's so we can have it all.

     

    3/08/2015 7:44 PM  #17

    josh-kebob
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    Re: Final gear ratio question

    terry wrote:

    Tubo wrote:

    Terry as you never drive your 2+2 to a Bash(Noooo Vandalia don't count) going with the more performance geared 3.55 will keep you happy. Leave the 3.25's fer the guy's who do the long distance cruising, and like the 26+ mpg.

    Tubo

    OUCH!!  that smarted just a tinge!!  I'll get even you just wait!!!

    t,
    says the guy who used your lift to fix his fuel issue............just sayin.......

     

    3/08/2015 8:01 PM  #18

    Tubo
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    Re: Final gear ratio question

    josh-kebob wrote:

    says the guy who used your lift to fix his fuel issue............just sayin.......

    j-kb, I just hope you have a lift ready fer me when the time comes, Hehheh.
    I'm guessing that you will host a Bash some time, and that I will be there.

    Tubo


     

    If it ain't broke, I haven't modified it Yet
     

    3/08/2015 8:12 PM  #19

    Steve69
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    Re: Final gear ratio question

    I started with built up 302 larger cam and had a 4 speed with a 4.56 axle.   I got sick of that in a hurry.   I went to a 3.25 gear with the 4 speed.   It still revved pretty high at 70 mph.   I switched to the T5Z and kept the 3.25 gears.  It runs great.  Doesn't chug or feel like its lugging.  When I punch it there no problem smoking the tires and it takes off Great.  Never checked the Gas Mileage.    Im running a 275-40-17 tire in the rear.  Steve69
     

     

    3/08/2015 9:30 PM  #20

    MS
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    Re: Final gear ratio question

    Steve69 brings up a good comparison. A car that is driven locally or on short trips may exhibit different manners than one you are living with on a long, constant highway cruise through various different terrains.

    I really believe best economy at cruise speed is achieved when the engine is running a little higher in the power band.   Every car and tune is unique as is everyone's perception of their own car's performance.

    Taking your car on a 2,000 mile trip with several days of highway cruising will let you find any shortcomings or tune issues, ratio issues, cooling issues, etc.

    Money you enjoy wasting is NOT wasted money... unless your wife finds out.
     

    3/08/2015 9:48 PM  #21

    TKOPerformance
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    Re: Final gear ratio question

    terry wrote:

    215/45-17

    That's a fairly short tire.  I'd stick with a 3.55 or numerically lower.

    Last edited by TKOPerformance (3/09/2015 3:21 AM)

     

    3/08/2015 10:20 PM  #22

    barnett468
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    Re: Final gear ratio question

    .
    unless your engine revs over around 5000 rpm and you race off the line often i would not 3.55 gears either . . 3.40 max but 3.25 would be best for highway at 70 mph and will still provide decent off the line acceleration . . you can also run a higher stall converter if need be.

    If you are trying to get the most mileage you can do the following:
     
    run a carb with annular boost venturis
     
    run your jetting on the lean side
     
    run an msd 6a box
     
    run a 192 – 195 thermostat.
     
    Set your initial timing and set your advance curve and vacuum diaphragm to provide the most timing your engine wants.
    .
     

    Last edited by barnett468 (3/08/2015 10:25 PM)

     

    3/09/2015 3:30 AM  #23

    TKOPerformance
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    Re: Final gear ratio question

    A 215/45R217 is a 24.5" tall tire.  Doing the math with a 3.55:1 rear gear and a 0.68 5th gear in a T5 you are turning 2,317RPM at 70MPH. 

    If running an AOD the 4th gear ratio is a 0.67, so you're right about the same RPM at 70. 

    I wouldn't consider that to be objectionable highway RPM.  For point of reference, with no OD you'd be turning 3,581RPM, which I would consider quite objectionable.

     

    3/09/2015 5:13 AM  #24

    Steve69
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    Re: Final gear ratio question

    MustangSteve wrote:

    Steve69 brings up a good comparison. A car that is driven locally or on short trips may exhibit different manners than one you are living with on a long, constant highway cruise through various different terrains.

    I really believe best economy at cruise speed is achieved when the engine is running a little higher in the power band. Every car and tune is unique as is everyone's perception of their own car's performance.

    Taking your car on a 2,000 mile trip with several days of highway cruising will let you find any shortcomings or tune issues, ratio issues, cooling issues, etc.

      Thats for sure MS.   When I had those 4.56 gears I had to wear Ear protection when I was on the HWY and was revving around 3800 rps at 55mph.    With the same engine and 3.25, T5Z its like I can hear my passenger talking instead of nodding my head yes...LOL   
     

     

    3/09/2015 5:45 AM  #25

    Jim Bowie
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    Re: Final gear ratio question

    When Mike and I drove down to Texas a few years back, with the 66 coupe, stock 289, 5 speed, with 3.25 rearend we would cruise  just above 2,000 rpm's, aronnd 70 mph, low 20's on fuel milage. I was having issues with rear end for the Montana bash so we put in the stock 2.,89 rear end in and would be cruising just below 2,000 rpm's at 70 mph and lost about 3 mpg on that trip. Went back to the 3.25 and never looked back.

     

     

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