Question about 95 formula stock drivetrain
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Joined: May 2008
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Question about 95 formula stock drivetrain
I test drove a 96 Z28 6-speed convertible back to back with my 95 auto formula when I was debating which one to buy. The Z28 had some mods...I'm not sure what all, but I know it had a diff exhaust and some diff gauges inside. Never lifted the hood cause I wasn't quite that serious about it yet. But the formula was stock, and it was quite a bit faster than the Z28. Mileage was close to the same...but the Z28 didn't have reverse, and seemed a little bit rougher than the formula, and of course was more spendy. But what really sold me was the diff in acceleration..I figured the 6 speed would be faster. That brings me to my question. My formula is an extremely strong running car for stock, and just lately I've been starting to wonder if somebody swapped rearend gears in it. It seems to have a slight bit of rearend slop, more than a 90k mile car should. Between that and the way it pulls I'm wondering if its been geared down. The speedo's always seemed to read a little high compared to our other cars and traffic in general.....at 70mph I'm turning 2000rpm's...at 65 I'm turning 1800...at 60 I'm turning 1600. Are those consistent with stock gearing for my car? Tires and rims are all stock size. It gets great mileage...so if its geared down it hasn't hurt fuel mileage much if any.
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Joined: Feb 2008
Posts: 502
From: Central Mass and NH
I test drove a 96 Z28 6-speed convertible back to back with my 95 auto formula when I was debating which one to buy. The Z28 had some mods...I'm not sure what all, but I know it had a diff exhaust and some diff gauges inside. Never lifted the hood cause I wasn't quite that serious about it yet. But the formula was stock, and it was quite a bit faster than the Z28. Mileage was close to the same...but the Z28 didn't have reverse, and seemed a little bit rougher than the formula, and of course was more spendy. But what really sold me was the diff in acceleration..I figured the 6 speed would be faster. That brings me to my question. My formula is an extremely strong running car for stock, and just lately I've been starting to wonder if somebody swapped rearend gears in it. It seems to have a slight bit of rearend slop, more than a 90k mile car should. Between that and the way it pulls I'm wondering if its been geared down. The speedo's always seemed to read a little high compared to our other cars and traffic in general.....at 70mph I'm turning 2000rpm's...at 65 I'm turning 1800...at 60 I'm turning 1600. Are those consistent with stock gearing for my car? Tires and rims are all stock size. It gets great mileage...so if its geared down it hasn't hurt fuel mileage much if any.
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From: Hell was full so they sent me to NJ
Those numbers would correspond roughly to a set of 4.10's. That assumes stock tire diameter, and that the PCM has been programmed with the correct rear axle ratio. With stock 3.42's, you'd be at about 1,600 RPM at 70MPH in 6th gear.
Jack it up, rotate the wheels exactly one turn, and count how many times the driveshaft turns.
Jack it up, rotate the wheels exactly one turn, and count how many times the driveshaft turns.
Thread Starter
Registered User
Joined: May 2008
Posts: 77
Those numbers would correspond roughly to a set of 4.10's. That assumes stock tire diameter, and that the PCM has been programmed with the correct rear axle ratio. With stock 3.42's, you'd be at about 1,600 RPM at 70MPH in 6th gear.
Jack it up, rotate the wheels exactly one turn, and count how many times the driveshaft turns.
Jack it up, rotate the wheels exactly one turn, and count how many times the driveshaft turns.
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