yet another gear thread!

Black04Stang · July 7th, 2008, 07:48 PM

i'm thinkin about 4.10s on my car but i havn't really heard anything from anyone with a auto trans... if any of you have this done let me know how it is as far as long highway trip, rear end heat, and rpms at like 80-85. thanks in advance!

thorpedo26 · July 7th, 2008, 08:38 PM

with an auto more people will choose 4:10's over 3:73's but its still personal preference. Theres a sticky at the top of the 99-04 section to look at if you havent already that will hep with further questions.

2kGT · July 7th, 2008, 09:01 PM

4.30s for an auto, 4.10s for a manual.

Black04Stang · July 7th, 2008, 09:36 PM

is there anything i can buy to beef up my trac loc too?

Black04Stang · July 7th, 2008, 10:38 PM

have any of you heard of driveline critical speed? i was reading that with the 4.10s at 76mph your driveline is spinning critically fast and you should be getting alot of vibrations and such.

RyanGT · July 7th, 2008, 10:44 PM

4.10s are fine, almost everybody gets them. Your differential will be fine unless you have serious power, and are running radials or slicks on a track.

Garhfer · July 7th, 2008, 11:31 PM

Originally Posted by Black04Stang

have any of you heard of driveline critical speed? i was reading that with the 4.10s at 76mph your driveline is spinning critically fast and you should be getting alot of vibrations and such.

uhm, that's funny because at like 76mph my car does shake a little, and I have 4.10's uhmm... I swapped out my tires and all and it still does it... my rotors and all are brand new too... maybe that's the reason... I was trying to figure it out I figured it was because of my tires or rotors but now I'm kind of lost.... lol

03SonicBoom · July 8th, 2008, 07:54 AM

Originally Posted by Black04Stang

have any of you heard of driveline critical speed? i was reading that with the 4.10s at 76mph your driveline is spinning critically fast and you should be getting alot of vibrations and such.

Every rotating shaft has a critical speed. It's just the nature of the material. Simple solution, don't drive at 76mph. Jump up/down 1 or 2 mph and it should stop.

cliffyk · July 8th, 2008, 08:17 AM

In 5th with a 3650 the driveshaft spins at 1.61 times engine speed, with 4.10 and lower gears the driveshaft can really get humming at speeds over 75. With the OEM 3.27 gears at 80 the engine's spinning 2200 rpm and the driveshaft at 3540 rpm. With 4.10s the driveshaft will be spinning around 4400 rpm at 80.

An aluminum driveshaft can help a lot as generally, and within reason, a lesser mass rotating object of given dimensions will exhibit a higher critical speed...

Roos85 · July 8th, 2008, 10:26 AM

Originally Posted by cliffyk

In 5th with a 3650 the driveshaft spins at 1.61 times engine speed, with 4.10 and lower gears the driveshaft can really get humming at speeds over 75. With the OEM 3.27 gears at 80 the engine's spinning 2200 rpm and the driveshaft at 3540 rpm. With 4.10s the driveshaft will be spinning around 4400 rpm at 80.

An aluminum driveshaft can help a lot as generally, and within reason, a lesser mass rotating object of given dimensions will exhibit a higher critical speed...

You sound like an engineer explaining this

DeMello · July 8th, 2008, 10:28 AM

Originally Posted by cliffyk

In 5th with a 3650 the driveshaft spins at 1.61 times engine speed, with 4.10 and lower gears the driveshaft can really get humming at speeds over 75. With the OEM 3.27 gears at 80 the engine's spinning 2200 rpm and the driveshaft at 3540 rpm. With 4.10s the driveshaft will be spinning around 4400 rpm at 80.

An aluminum driveshaft can help a lot as generally, and within reason, a lesser mass rotating object of given dimensions will exhibit a higher critical speed...

holy fuck lol

cliffyk · July 8th, 2008, 11:23 AM

I am, BSME MIT '71...

Black04Stang · July 8th, 2008, 03:29 PM

so what your tryin to say is, if im gonna get 4.10s and i wanna go faster than 75 or 80 i should invest in either a carbon fiber, or aluminum driveshaft?

oh2swapped · July 8th, 2008, 03:32 PM

there a guy rolling around by me with an auto GT and he has 4.56's in his

KhaosGT · July 8th, 2008, 03:34 PM

Originally Posted by cliffyk

In 5th with a 3650 the driveshaft spins at 1.61 times engine speed, with 4.10 and lower gears the driveshaft can really get humming at speeds over 75. With the OEM 3.27 gears at 80 the engine's spinning 2200 rpm and the driveshaft at 3540 rpm. With 4.10s the driveshaft will be spinning around 4400 rpm at 80.

An aluminum driveshaft can help a lot as generally, and within reason, a lesser mass rotating object of given dimensions will exhibit a higher critical speed...

oh no ive gone crosseyed

03SonicBoom · July 8th, 2008, 03:35 PM

Originally Posted by Black04Stang

so what your tryin to say is, if im gonna get 4.10s and i wanna go faster than 75 or 80 i should invest in either a carbon fiber, or aluminum driveshaft?

No, what he's saying is if you avoid 76 mph you'll be fine. Critical speed on a rotating shaft is only at a specific speed (multiple speeds but the first harmonic is the worst and most likely the only one to worry about). Get above or below 76 mph (the critical speed) and the vibrations will go away.

cliffyk · July 8th, 2008, 03:47 PM

Originally Posted by 03SonicBoom

No, what he's saying is if you avoid 76 mph you'll be fine. Critical speed on a rotating shaft is only at a specific speed (multiple speeds but the first harmonic is the worst and most likely the only one to worry about). Get above or below 76 mph (the critical speed) and the vibrations will go away.

Also, you might get lucky and have an only minimal problem, not going 76 is easy too...

That said, an aluminum driveshaft (carbon fibre is a waste of $$) is near the top of my "next mod" list. It's about the cheapest and easest way there is to reduce driveline inertia.

Smoothgrandmama · July 8th, 2008, 03:50 PM

GET 3.73's for your auto. . . . unless you drive only 65 on the highway

2kGT · July 8th, 2008, 09:27 PM

This entire thread is the largest collection of utter bullsh1t I have ever heard. Except for the part where I said get 430s for your auto.

Yella01Stang · July 24th, 2008, 10:26 PM

Lol, 4.10+ is the only way to go n/a...Autos could go steeper

July 7th, 2008, 07:48 PM	#1
Black04Stang Newbie 2004 Mustang GT ? Join Date: Jul 2008 Location: London, KY Posts: 17	yet another gear thread! i'm thinkin about 4.10s on my car but i havn't really heard anything from anyone with a auto trans... if any of you have this done let me know how it is as far as long highway trip, rear end heat, and rpms at like 80-85. thanks in advance!

July 7th, 2008, 09:01 PM	#3
2kGT Regular Join Date: Oct 2007 Location: Upstate SC Posts: 489	4.30s for an auto, 4.10s for a manual. __________________ Accufab 75mm tb & plenum MRT h-pipe Flowmaster catback FRPP king cobra clutch FRPP aluminum driveshaft FRPP 4.10 gear TA Perfromance girdle Steeda tri-ax shifter Moser 31 spline axles FRPP C Springs

July 7th, 2008, 10:44 PM	#6
RyanGT Enthusiast 2000 GT Join Date: Dec 2006 Location: Washington Posts: 823	4.10s are fine, almost everybody gets them. Your differential will be fine unless you have serious power, and are running radials or slicks on a track. __________________ 2000 Black convertible GT: KB 15psi, and other goodies...

July 8th, 2008, 08:17 AM	#9
cliffyk Regular Join Date: Feb 2007 Location: Saint Augustine, FL Posts: 382	In 5th with a 3650 the driveshaft spins at 1.61 times engine speed, with 4.10 and lower gears the driveshaft can really get humming at speeds over 75. With the OEM 3.27 gears at 80 the engine's spinning 2200 rpm and the driveshaft at 3540 rpm. With 4.10s the driveshaft will be spinning around 4400 rpm at 80. An aluminum driveshaft can help a lot as generally, and within reason, a lesser mass rotating object of given dimensions will exhibit a higher critical speed... __________________ -cliff knight- My Mustang GT Multi-fuel: Burns gas and rubber...

July 8th, 2008, 11:23 AM	#12
cliffyk Regular Join Date: Feb 2007 Location: Saint Augustine, FL Posts: 382	I am, BSME MIT '71... __________________ -cliff knight- My Mustang GT Multi-fuel: Burns gas and rubber...

July 7th, 2008, 09:36 PM	#4
Black04Stang Newbie 2004 Mustang GT ? Join Date: Jul 2008 Location: London, KY Posts: 17	is there anything i can buy to beef up my trac loc too?

July 7th, 2008, 10:38 PM	#5
Black04Stang Newbie 2004 Mustang GT ? Join Date: Jul 2008 Location: London, KY Posts: 17	have any of you heard of driveline critical speed? i was reading that with the 4.10s at 76mph your driveline is spinning critically fast and you should be getting alot of vibrations and such.

July 8th, 2008, 03:29 PM	#13
Black04Stang Newbie 2004 Mustang GT ? Join Date: Jul 2008 Location: London, KY Posts: 17	so what your tryin to say is, if im gonna get 4.10s and i wanna go faster than 75 or 80 i should invest in either a carbon fiber, or aluminum driveshaft?

July 8th, 2008, 03:32 PM	#14
oh2swapped Regular 02 Mustang GT 17.8@16.44 Join Date: Sep 2007 Location: Land O Lakes FL Posts: 289	there a guy rolling around by me with an auto GT and he has 4.56's in his __________________ NEXT TO SEX, MY MUSTANG IS BEST

July 8th, 2008, 03:50 PM	#18
Smoothgrandmama Editor Join Date: Apr 2007 Location: Willis,Texas Posts: 1,856	GET 3.73's for your auto. . . . unless you drive only 65 on the highway __________________

July 8th, 2008, 09:27 PM	#19
2kGT Regular Join Date: Oct 2007 Location: Upstate SC Posts: 489	This entire thread is the largest collection of utter bullsh1t I have ever heard. Except for the part where I said get 430s for your auto. __________________ Accufab 75mm tb & plenum MRT h-pipe Flowmaster catback FRPP king cobra clutch FRPP aluminum driveshaft FRPP 4.10 gear TA Perfromance girdle Steeda tri-ax shifter Moser 31 spline axles FRPP C Springs

July 24th, 2008, 10:26 PM	#20
Yella01Stang Regular Join Date: Nov 2007 Posts: 77	Lol, 4.10+ is the only way to go n/a...Autos could go steeper __________________ 2001 GT Stang "Bullitt #5583 wanna-be" Best ET 13.8 104mph (b4 motor/gear) D.S.S. ProMod ShrotBlock, DiabloSport Predator, Steeda TriAX, FRPP 4.10s & D-shaft, FRPP 24# injct, Flowmasters, 03 Cobra Brakes, one awesome tune & much more ;]

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