correct RPM for 5 speed?

[kensmith]

I was on the freeway and at 70 MPH and I was taching 4,000 RPM in 5th gear. Does that seem right? 1978 124 spider.

[Gregors]

Seems pretty close to me. I'm not sure what your pumpkin is in a 78, but in my 75 it is the 4.3 to 1 so it has to rev pretty high. The more ive driven tho, the more I realize how much my engine likes to rev between 4 and 5k.

Ive done a lot of sound proofing thought, and it doesnt seem near as loud as it did when I got it

[mdrburchette]

That's about right. Like Gregors says, they're made to rev.

[Exit98]

4200 RPM at 70 MPH per my GPS

[puddin]

THE HIGH WHINE AT 70 MPH FOR AN HOUR COMMUTE TO WORK IS A LOT TO TAKE-- I FOUND SOME 185/80/13 TIRES THAT DROPPED ABOUT 500 RPM

[wikkid]

THE HIGH WHINE AT 70 MPH FOR AN HOUR COMMUTE TO WORK IS A LOT TO TAKE-- I FOUND SOME 185/80/13 TIRES THAT DROPPED ABOUT 500 RPM

's ok - we can hear you just fine

[So Cal Mark]

ya gotta yell over the high whine! 185/80 sorta look like pizza cutters don't they?

[puddin]

na -- kinda give the car a slight lean forward. i also noticed that if you draft a 18 wheeler at 70 + mph it quiets things down and get better gas mileage but for some reason it pisses the driver off.

[Eastlight]

I just returned from a 2000 mile round trip beginning in S. NJ to southern Georgia and back, total of 9.5 tanks of gas used by my '80 Spider (carburator). I was tacking about 4000 rpm at 75mph (GPS indicated speed). Nice that from Virginia to Georgia and back, most posted highway speeds are 70mph and no tolls after Maryland.
Don't think I'll make the trip again in my Fiat since at that speed the wind whistling around the convertable top makes a lot of noise during the 15 hour drive (only stopping for gas and lunch). I enjoyed the 2-lane highway around Macon, GA, which was hilly, curvy, light traffic and easily managed by the Fiat at 70mph.
Will post the only difficulty I had under "electrical" (thanks to my sister ).

[fiat2000]

I have a 79 5 speed with an automatic rear end, at 60mph I'm only reving at 3000 rpm, and i have the 205/60/13 wheels. 5000 rpm gets me just over 100 mph! and the cars wants to keep going!!

[mdrburchette]

Does it have any umph on the bottom end? Mine's got the 4:30 rear end and it revs on up there but it doesn't bother me to buzz around at 75.

[baltobernie]

See if you can get Erskine to bring his purple Spider to FFO or Dixie; it has the auto rear, 2-liter stock except twin 40's. Really nice to drive, you'll see.

[mdrburchette]

He brought it in '09. I'll have to ask for a ride this year.

[puddin]

excuse my ignorance but the "auto rear end" ??

is that an automatic trans?

or some sort of two speed rear axle???

are you referencing the auto differentals being 3.90 and that's why it has a lower cruise rpm??

[baltobernie]

Yes, I'm referring to a rear differential from an automatic transmission Spider, which came with a 3.56 ratio vs. 4.3 (pre-'78) or 3.9 ('78+) manual transmission cars. Tire size of course also affects final drive ratio. The cars originally came with tires approximately 73" in circumference. Bigger than that, RPMs decrease, and acceleration suffers, and vice versa.