My RPMs are only 2,000 when going 80mph. what is up with that?

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92' White Pontiac Firebird V8 305 TBI

 

Sounds like you are the lucky owner of a 2.77 rear.

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1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, MSD coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley module, ported plenum,
Ported Daytona Yellow stock base, Moroso valve covers, other stuff,
Streetdampr, Ruger P95DC, hot wife, new oil filter, !cats, !TBC, !AIR.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

That sounds normal if it is an automatic. I do not know about the standard. My GTA will cruise at about 1600 RPM @ 55MPH on overdrive. At 80 MPH it will be about 2100 RPM.
Can't remember exactly the numbers but that is a ballpark figure.
This is with a 3.21 rearend.

[This message has been edited by Ozzy88GTA (edited September 08, 2001).]

 

what is 2.77 rear?? is it good or bad?

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92' White Pontiac Firebird V8 305 TBI

 

That's the gear ratio of your rear end. Basically, the higher gears (numerically lower) offer higher top speed and better gas milage(result of low RPM cruising). Lower gears (numerically higher) such as 3.73:1 will offer better acceleration, lower top speed and lower gas milage.



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-Dan
-1990 3.1L RS
-Mods? no
-Slow? yes
-Currently collecting parts for T5 swap

 

Not always, with my particular cam my mileage improved very slightly going from a 2.73 to a 3.54.

 

92,

Jethro is on the right track - you have a low-ratio ring/pinion gear set. However, the 2.77:1 axle wasn't available in 1992, since the axles in that year were all Saginaw units, not Borg Warner. The ratio is probably 2.73:1.

That's great for cruising fuel economy, and for higher top-end, but not so good for accelleration. You can compensate for the low ratio by altering the stall characteristics of the torque converter, and still have decent highway fuel mileage. You and I are lucky enough to live where we can actually drive 70-80 MPH (or more if we feel like it) for hours on end without having to brake for a nine-lane-wide parking lot.

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Later,
Vader
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"Click - Click - BOOM!"
Adobe Acrobat Reader

[This message has been edited by Vader (edited September 09, 2001).]

 

With a 3.06 first gear in a 700R-4, it's way too easy to put in too big(numerically high) rear end. I have 3.08s, and don't plan on swapping any time soon, and wouldn''t think of going any more than 3.42-3.45. I'm assuming that the poster of this topic won't be hitting the strip often enough that would justify the change in mileage and what speed the power band is at. just my two cents

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'84 Berlinetta, LG4, 700R-4, starwars interior, falling headliner, T/A t-handle shifter, trans cooler, more to come in time and $$ www.hipergp@aol.com

 

im assuming you have an automatic...im saying this because i have a LB9 w/ a 3.08 rear,and in 5th gear i run 80MPH at 2000rpms
if you do have an auto,yup you got 2.77's

Andy

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