High RPMS - The 1947 - Present Chevrolet & GMC Truck Message Board Network

69ChevySB · 01-20-2003, 10:50 PM

Hi there folks, I was wondering what I could do to get lower rpms at higher speeds....when i'm goin down the freeway or highway it sounds like my motor is gonna explode because i'm going like 75 and my rpms is like 3500-4000 at that speed...what can I do to prevent my rpms from going so high? Maybe it's because I have a 3 speed on the floor and it feels as if I need another gear to throw it in...would it make a difference if I put a 4 speed in, or automatic transmission? Thanks.

mooneyes · 01-20-2003, 10:58 PM

a 4 speed or automatic ( unless an overdrive) wont make a difference..you need either a rearend with higher gears ( numerically lower) or an overdrive tranny

Truckstr · 01-20-2003, 10:59 PM

It's the gearing.

The combination of a low (high numerical) rear and 1:1 top gear ratio tranny amount to high RPM at normal highway cruising speeds.

You can change the 'effective' rear gear ratio by going to really tall rear tires, but IMO the only correct way to do it is with a higher (lower numerical) rear gear AND/OR a overdrive tranny.

What's your budget?

Jeff

spinning wheels · 01-21-2003, 12:08 AM

Try taller tires

71GMC_3/4T · 01-21-2003, 12:22 AM

Put on a 4 speed shifter knob?

Sorry....

Change the rear axle gear ratio.

01-20-2003, 10:50 PM	#1
69ChevySB dropped69 Join Date: Jan 2003 Location: Grand Canyon State Posts: 120	High RPMS Hi there folks, I was wondering what I could do to get lower rpms at higher speeds....when i'm goin down the freeway or highway it sounds like my motor is gonna explode because i'm going like 75 and my rpms is like 3500-4000 at that speed...what can I do to prevent my rpms from going so high? Maybe it's because I have a 3 speed on the floor and it feels as if I need another gear to throw it in...would it make a difference if I put a 4 speed in, or automatic transmission? Thanks.

01-20-2003, 10:58 PM	#2
mooneyes Registered User Join Date: Jan 2002 Location: Slippery Rock PA USA Posts: 1,692	a 4 speed or automatic ( unless an overdrive) wont make a difference..you need either a rearend with higher gears ( numerically lower) or an overdrive tranny __________________ Ken Lyons, Slippery rock pa 68 short step 327 t10 4 gear 72 2wd blazer project 70 lwb 305/700r driver 78 caprice project 02 cavalier D.D ( hate it!!)

01-20-2003, 10:59 PM	#3
Truckstr Registered User Join Date: Nov 2002 Location: Lebanon, Tennessee Posts: 1,372	It's the gearing. The combination of a low (high numerical) rear and 1:1 top gear ratio tranny amount to high RPM at normal highway cruising speeds. You can change the 'effective' rear gear ratio by going to really tall rear tires, but IMO the only correct way to do it is with a higher (lower numerical) rear gear AND/OR a overdrive tranny. What's your budget? Jeff __________________ Jeff '67 short Fleet; my ongoing project. '66 long Fleet; my original "baby." Live life or bust trying.

01-21-2003, 12:08 AM	#4
spinning wheels Registered User Join Date: Sep 2001 Location: Hacienda Heights, California USA Posts: 474	Try taller tires __________________ '72 GMC custom camper 350/350

01-21-2003, 12:22 AM	#5
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	Put on a 4 speed shifter knob? Sorry.... Change the rear axle gear ratio. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO

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