Doubleaction

Hey guys, I just recently bought a 98 z28 and when im cruising on the highway at 80mph im at 2500rpm. This is not my first Camaro and I know that isn't normal. The previous owner didn't own the car for more than a month due to receiving it on a trade so doesn't really know whats done to it other than he says it may have a mildly built trans and a rebuilt rearend. It does have 315 Nitto 555's on it which im thinking it might have a different gear in it. Kind of stupid since the cars suspension isn't that good, nor is it frame tied. Could it be that it has 4.10s or a higher type gear that is causing this? I know its in overdrive because the rpms go even higher if I take it out.

FasTimeSS

iTrader: (47)

Sounds like it has 3.42s in it what trans is it? Give some more details

ZEEYAL8R

my 94 z is the same way. sounds like 3.42s to me.

FirstYrLS1Z

iTrader: (4)

M6 or A4 ?

Doubleaction

Its an a4

1 FMF

iTrader: (1)

http://www.f-body.org/gears/

A4 cars with 4th gear ratio being 0.70, and rear axle ratio of 3.23, 84mph shows 2500 rpm in 4th gear. a 3.42 rear axle ratio shows 80mph at 2500 rpm.

the other thing is if the axle ratio was changed, the computer needs to be flashed with that new ratio otherwise your speedometer is off. you need to use gps on the highway to verify your speedometer is correct before you try figuring out anything- unless you pull the axle cover and count teeth or identify the ring gear.

FirstYrLS1Z

iTrader: (4)

In the/your original post,you mentioned overdrive. 4th gear(.70) is overdrive,but you didn't state whether that was with convertor unlocked or locked. There could be a difference of 300rpm for that.

Doubleaction

Thanks guys.

I don't know what you mean by the converter locked or unlocked. Its just in overdrive and at 80mph I'm at 2500rpm.

FirstYrLS1Z

iTrader: (4)

Convertor locked-no typical torque convertor slippage-acts like a M6 direct drive clutch
Convertor unlocked-convertor is acting like a typical non-lockup convertor and 'slipping'-engine rpm/torque convertor input rpm is higher than torque convertor output rpm.

jimmyblue

iTrader: (11)

Sounds exactly like my A4 with 3.42s and 17" rims.

01ssreda4

iTrader: (96)

Sounds like a stock 3.23 gear to me. Sounds normal or very close to. Whats all the fuss about?

ZEEYAL8R

i payed attention to my 94 z today on the highway cause i had this thread on my mind, i was cruising down the highway at 75 mph, 2750 rpms. auto car.

joecar

mph * 336 * (gr) / td = rpm

80 * 336 * (0.696 * 3.23) / 25.66 = 2355
80 * 336 * (0.696 * 3.42) / 25.66 = 2493

DemonicZ

I have a 98Z A4 2.73s on stock 16s and turn 2600@80mph I don't hit 3000rpm until 95

joecar

Not if you have 2.73.

edit: sounds like you have 3.56's:
80 * 336 * (0.696 * 3.56) / 25.66 = 2596

1981TA

iTrader: (7)

I don't see what the fuss is either.

3.73s, M6, 2000 RPM @ 80 MPH in 6th. The engine seems happier in 5th at that speed, but oh well.