Recent Topics
What’s the odds..
by Eric Smith
06/19/18 09:51 PM
Who can relate?
by Reddy45
06/19/18 09:43 PM
No more oil changes
by goodtimes
06/19/18 09:19 PM
Separating toddlers from their parents?
by fdcg27
06/19/18 08:50 PM
gm 8.6 truetrac
by Spitter
06/19/18 08:45 PM
New addition to my garage: 2000 Corvette FRC
by MrHorspwer
06/19/18 08:34 PM
Rockauto 5% off
by Spitter
06/19/18 08:32 PM
fumoto oil valve
by Santo
06/19/18 08:19 PM
Grand solar minimum...
by ridgerunner
06/19/18 07:57 PM
Pentofrost coolant $10 Autozone
by PD001
06/19/18 07:49 PM
The things you find cleaning Garage 30+ btls slob
by digger327
06/19/18 07:20 PM
Castrol GTX Magantec 0w20 - 6 pack $21.99 - Amazon
by 04SE
06/19/18 07:07 PM
Havoline Pro DS 5w20 $3.15/quart - Amazon
by 04SE
06/19/18 07:06 PM
Needing New Dipstick
by Geauxtiger
06/19/18 05:11 PM
'98 Mercedes E300TD Rotella T5 10W-30 5k miles
by KenO
06/19/18 04:35 PM
Premium guard oil filters
by Jaha24k
06/19/18 04:09 PM
76 super motor oil- synthetic blend 5w-30
by Jaha24k
06/19/18 04:07 PM
Who makes the Mopar 5038041AA filter?
by Quattro Pete
06/19/18 03:55 PM
Ruger Mini-14, yay or nay?
by 28oz
06/19/18 03:51 PM
USPS long long delivery to BlackStone Labs
by Pajero
06/19/18 02:58 PM
Newest Members
Shassis, Santo, aligoodn, memyself, MichiganKid419
65274 Registered Users
Who's Online
79 registered (77GrandPrix, 2015_PSD, BigCahuna, Aero540T, 7 invisible), 1333 Guests and 42 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
65274 Members
67 Forums
285627 Topics
4766614 Posts

Max Online: 3590 @ 01/24/17 08:07 PM
Donate to BITOG
Page 1 of 2 1 2 >
Topic Options
#4517754 - 09/16/17 11:20 AM Understanding gears
Camprunner Offline


Registered: 02/19/08
Posts: 1034
Loc: MA.
I was wondering about rear end gear ratios for example my 2013 Mustang GT has a 3:73 rear axle ratio so does that mean that the rear wheel turns 3:73 times for every one revolution of the engine? I know that 3:73 is a lower gear then the other ratios for the Mustang being 3:55 or 3:33 and it gives you more acceleration off the line with the negative being lower fuel millage. But I don't quite understand how to explain it? Is 3:73 where one wheel turns 3:73 times with one complete engine revolution?

Thanks!

Top
#4517757 - 09/16/17 11:27 AM Re: Understanding gears [Re: Camprunner]
4WD Offline


Registered: 09/21/10
Posts: 6366
Loc: Texas
Ring 41 teeth - pinion 10 teeth 41/10= 4.10 gear ratio

Top
#4517758 - 09/16/17 11:28 AM Re: Understanding gears [Re: Camprunner]
69GTX Offline


Registered: 09/23/15
Posts: 3815
Loc: Connecticut
Google is your friend

If your ratio is 3.73, the drive shaft turns 3.73 times for each turn of the rear wheel.
_________________________
----------------

2001 Lincoln Cont 4.6L DOHC/ 39K mi / QS HM 5w30 / FUG XG2
1999 Camaro SS M6 /19K /Mobil 1 0w40 /Fram UG /GM MTL-ATF
1969 Ply GTX/RRs

Top
#4517764 - 09/16/17 11:45 AM Re: Understanding gears [Re: Camprunner]
spasm3 Offline


Registered: 05/30/10
Posts: 8646
Loc: North Carolina
3.73 turns of the drive shaft for each 360 of the wheel/axle.
_________________________
13 elantra 68k 5w30 QSUD
03 chevy avalanche76k synpwr 10w30
01 saturnsc1 185k synpwr rebuilt
17 mazda cx-5 3900 miles m1 0w20/0w40 mix

Top
#4517772 - 09/16/17 11:53 AM Re: Understanding gears [Re: Camprunner]
Alex_V Offline


Registered: 04/10/16
Posts: 1155
Loc: Campbellsville, KY
It's the ratio of input vs. output speed of the differential - 3.73 tevs of the driveshaft to one of the wheels. Whether that correlates to engine RPM's depends what the transmission is. A manual transmission with no overdrive, in high gear? Yes. Non-overdrive automatic? Slightly higher engine speed. Overdrive? Engine RPM will be lower to the tune of whatever the transmission's OD ratio is.
_________________________
I like Chevy and Valvoline.

'13 Cruze, 1.4T, 112K
'85 GMC C3500, 454, 130K
'82 Mercedes 300CD, OM617 turbo, 167K
'67 Suburban, 350, 331K

Top
#4517774 - 09/16/17 11:54 AM Re: Understanding gears [Re: 69GTX]
ArcticDriver Offline


Registered: 01/27/17
Posts: 1139
Loc: USA
Originally Posted By: 69GTX
Google is your friend

If your ratio is 3.73, the drive shaft turns 3.73 times for each turn of the rear wheel.


I say half right.

The explanation was right on the money but the part about Google being our friend is a claim I ambeginning to doubt.
A friend respects your privacy.
grin
_________________________
Multiple Diesel and Gasoline vehicles

Top
#4517785 - 09/16/17 12:06 PM Re: Understanding gears [Re: Camprunner]
Kuato Offline


Registered: 10/23/05
Posts: 7094
Loc: Colorado
Originally Posted By: Camprunner
I was wondering about rear end gear ratios for example my 2013 Mustang GT has a 3:73 rear axle ratio so does that mean that the rear wheel turns 3:73 times for every one revolution of the engine? I know that 3:73 is a lower gear then the other ratios for the Mustang being 3:55 or 3:33 and it gives you more acceleration off the line with the negative being lower fuel millage. But I don't quite understand how to explain it? Is 3:73 where one wheel turns 3:73 times with one complete engine revolution?

Thanks!


Numbers above are correct....a higher ratio, say 4:11 to 1, allows the driveshaft to turn faster than a 3.73, so it is easier for the engine to accelerate the vehicle. You lose (potentially) some top speed and mpg at the expense of that performance.
_________________________
Thick vs Thin test: 15k / 43k miles complete

Top
#4517790 - 09/16/17 12:10 PM Re: Understanding gears [Re: Camprunner]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 18948
Loc: Sunny Florida
Yep. Not as important today with multi speed transmissions. My 2014 RAM has a 3.91 rear gear and with two overdrives it is still happy at highway speeds.
_________________________
"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix

Top
#4517816 - 09/16/17 12:36 PM Re: Understanding gears [Re: Camprunner]
WyrTwister Offline


Registered: 01/13/13
Posts: 1505
Loc: Texas
Originally Posted By: Camprunner
I was wondering about rear end gear ratios for example my 2013 Mustang GT has a 3:73 rear axle ratio so does that mean that the rear wheel turns 3:73 times for every one revolution of the engine? I know that 3:73 is a lower gear then the other ratios for the Mustang being 3:55 or 3:33 and it gives you more acceleration off the line with the negative being lower fuel millage. But I don't quite understand how to explain it? Is 3:73 where one wheel turns 3:73 times with one complete engine revolution?

Thanks!


Drive shaft turns 3.73 times for each revolution of the axles .

Best wishes , :-)
_________________________
Wyr
God bless

Top
#4517819 - 09/16/17 12:40 PM Re: Understanding gears [Re: SteveSRT8]
WyrTwister Offline


Registered: 01/13/13
Posts: 1505
Loc: Texas
Originally Posted By: SteveSRT8
Yep. Not as important today with multi speed transmissions. My 2014 RAM has a 3.91 rear gear and with two overdrives it is still happy at highway speeds.


Tire diameter plays an important part , too . The larger the tire diameter , the further the car travels with each revolution of the tire .

As far as engine rpm , this has the same effect as a slightly lower numeric deferential ratio .

Best wishes , :-)
_________________________
Wyr
God bless

Top
#4517865 - 09/16/17 01:31 PM Re: Understanding gears [Re: WyrTwister]
Kira Offline


Registered: 08/19/10
Posts: 5214
Loc: Champlain/Hudson Valley
Just to punctuate this thread-not to highjack it.

My Dad had a 1970 Mercury Monterey 400-2V (spelled OINK-OINK) which had a 1.75 rear end. It had the C6 transmission.

Even cars with "economy rear axles" (some Cadillacs were so marketed during a gas shortage) weren't as long legged as that Mercury.

Anybody experience a higher rear axle ratio?

Top
#4517875 - 09/16/17 01:46 PM Re: Understanding gears [Re: Camprunner]
02SE Offline


Registered: 12/30/05
Posts: 2727
Loc: The Canyons
I believe the tallest gear set Mercury offered was 2.50:1.

I know of taller custom gear sets in custom differentials, than 1.75:1, but they are in Landspeed vehicles.

Top
#4517936 - 09/16/17 03:26 PM Re: Understanding gears [Re: Camprunner]
eljefino Offline


Registered: 06/15/03
Posts: 32632
Loc: ME
I've always figured the actual proper terminology would be 1:3.73 but the 1: gets dropped in casual notation.

Motor trend etc when they do a car test will list a chart that includes "engine RPM at 60 MPH in high gear" to combine the cumulative effects of overdrive transmissions, tire size, and axle ratio.

Top
#4517959 - 09/16/17 04:14 PM Re: Understanding gears [Re: Kira]
Kuato Offline


Registered: 10/23/05
Posts: 7094
Loc: Colorado
Originally Posted By: Kira
Just to punctuate this thread-not to highjack it.

My Dad had a 1970 Mercury Monterey 400-2V (spelled OINK-OINK) which had a 1.75 rear end. It had the C6 transmission.

Even cars with "economy rear axles" (some Cadillacs were so marketed during a gas shortage) weren't as long legged as that Mercury.

Anybody experience a higher rear axle ratio?


That's the tallest ratio I've heard of. I know some Chrysler products from the 70s had 2.76.

My brother built a 440 into an early 70s Road Runner....727 automatic and 3.21, it would chirp leave long black streaks (as the rear end walked sideways a bit) on the road when it shifted into third gear. At around 120mph.
_________________________
Thick vs Thin test: 15k / 43k miles complete

Top
#4518071 - 09/16/17 06:52 PM Re: Understanding gears [Re: 02SE]
WyrTwister Offline


Registered: 01/13/13
Posts: 1505
Loc: Texas
Originally Posted By: 02SE
I believe the tallest gear set Mercury offered was 2.50:1.

I know of taller custom gear sets in custom differentials, than 1.75:1, but they are in Landspeed vehicles.





As a teen ager , I drove a 1966 Comet 289 . The rear end ratio was numerically slightly smaller that 3 : 1 . Had 14" wheels which partially compensated for the high differential gearing .

Best wishes , ;-)
_________________________
Wyr
God bless

Top
Page 1 of 2 1 2 >