anyone else run LOW cruise RPM's? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tom · 11-22-2002, 05:53 PM

Well I just figured my RPM's at speed once my 2004R swap will be finished. 1377rpm at 50mph, a little over 2000rpm at 80mph. WOW! Thats LOW. And this is with 3.54 rear gears. Does anyone else run this low of RPM's? Do you have any problems with it this low? Gas milage pretty good?

**swervin ervin** · 11-22-2002, 07:08 PM

Tom,

I run right at 2000 rpm at 70 or just a hair over, with 3.73 gears and 27" tires. This is with my .70 OD ratio. But the lockup converter lowers it about 200 rpm.

Check this page.

http://www.73-87.com/convers_calcus/equation1.htm

And here's the best one on the net for stuff like this.

http://www.bgsoflex.com/auto.html

Big Paul · 11-23-2002, 06:31 PM

At 80MPH it cruises around 2600RPM. 700r4, 3.42 rear.

gchemist · 11-23-2002, 08:38 PM

Gear 1_ 2_ 3_ 4_
500_ 4.1 _ 7.7 _ 12.6 _ 18.0 _
1000_ 8.2 _ 15.5 _ 25.2 _ 36.0 _
1500_ 12.4 _ 23.2 _ 37.8 _ 54.0 _
2000_ 16.5 _ 30.9 _ 50.4 _ 72.0
2500_ 20.6 _ 38.7 _ 63.0 _ 90.0 _
3000_ 24.7 _ 46.4 _ 75.6 _ 108.0 _
3500_ 28.8 _ 54.1 _ 88.2 _ 126.1 _
4000_ 33.0 _ 61.9 _ 100.8 _ 144.1 _
4500_ 37.1 _ 69.6 _ 113.4 _ 162.1 _
5000_ 41.2 _ 77.3 _ 126.1 _ 180.1 _
5500_ 45.3 _ 85.1 _ 138.7 _ 198.1 _

18 MPG on my 305 smog pump.

My truck likes OD at least 1800 RPM or higher. Anything lower and it bogs down.

Txstruck · 11-23-2002, 11:09 PM

Lets see:

55mph=~3100rpm w/4.56 gears and STILL gets 25-27mpg!

11-22-2002, 05:53 PM	#1
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,748	anyone else run LOW cruise RPM's? Well I just figured my RPM's at speed once my 2004R swap will be finished. 1377rpm at 50mph, a little over 2000rpm at 80mph. WOW! Thats LOW. And this is with 3.54 rear gears. Does anyone else run this low of RPM's? Do you have any problems with it this low? Gas milage pretty good? __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

11-22-2002, 07:08 PM	#2
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Tom, I run right at 2000 rpm at 70 or just a hair over, with 3.73 gears and 27" tires. This is with my .70 OD ratio. But the lockup converter lowers it about 200 rpm. Check this page. http://www.73-87.com/convers_calcus/equation1.htm And here's the best one on the net for stuff like this. http://www.bgsoflex.com/auto.html __________________ Mike 1985 Chevy C-10

11-23-2002, 06:31 PM	#3
Big Paul Iamnotanofficerofthelaw Join Date: Feb 2002 Location: Turlock, California Posts: 352	At 80MPH it cruises around 2600RPM. 700r4, 3.42 rear. __________________ ~Paul~ '96 C1500 Silverado- Vortec 5.0L/Exhaust/Stock '87 S-10 Ext Cab- 2.8L/700r4 KIA Caught fire 12/7/03

11-23-2002, 08:38 PM	#4
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Gear 1_ 2_ 3_ 4_ 500_ 4.1 _ 7.7 _ 12.6 _ 18.0 _ 1000_ 8.2 _ 15.5 _ 25.2 _ 36.0 _ 1500_ 12.4 _ 23.2 _ 37.8 _ 54.0 _ 2000_ 16.5 _ 30.9 _ 50.4 _ 72.0 2500_ 20.6 _ 38.7 _ 63.0 _ 90.0 _ 3000_ 24.7 _ 46.4 _ 75.6 _ 108.0 _ 3500_ 28.8 _ 54.1 _ 88.2 _ 126.1 _ 4000_ 33.0 _ 61.9 _ 100.8 _ 144.1 _ 4500_ 37.1 _ 69.6 _ 113.4 _ 162.1 _ 5000_ 41.2 _ 77.3 _ 126.1 _ 180.1 _ 5500_ 45.3 _ 85.1 _ 138.7 _ 198.1 _ 18 MPG on my 305 smog pump. My truck likes OD at least 1800 RPM or higher. Anything lower and it bogs down. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

11-23-2002, 11:09 PM	#5
Txstruck Registered User Join Date: Nov 2002 Location: Dallas Posts: 459	Lets see: 55mph=~3100rpm w/4.56 gears and STILL gets 25-27mpg! __________________ Steve 86 K30 4x4 6.2L Diesel\TH400\NP208 - 14bolt FF rear w/detroit locker and Dana60 front w/detroit locker- both with 4.56 gears "Runs on Mud"



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