6th gear? Any solutions to better top end?

[giuliot60]

How many of you wish you had a sixth gear in the car?

I'm not racing the car and like to cruise on the highway. Low end is great, I can almost get the car going from a dead stop in 2nd gear and would like to have more options for my top end. My 81 does 60 at about 3K rpms and I would like to get her to cruise at 70 at that rpm. Is that possible with a rear end gear change, transmission or engine mod, or am I just fantasizing?

I have Falken 912s size 195/60/14.

Curious.

[kmead]

You can put an automatic rear end in the car which will drop rpm significantly but sacrifice lower end but being a turbo that will be less of an issue.

[azruss]

i guess my issue with this is you are adding alot of stress to the bottom half of the engine. You are also moving farther away from the rpms that produce the best power. when you add these together, you are forcing your motor to work harder, (ie wear faster) with poorer fuel economy. these motors are designed to work hard in the mid rpm range. This is not an american V8, dont try to make it act like one.

[JammerX19]

The 5th gear ratio is already 0.83. Correct me if I'm wrong, but I thought 6-speed transmissions just provided a smoother gear range but didn't necessarily add a gear with a lower ratio. My frame of reference is my bicycle...went from 8-speed cluster to 10-speed cluster and the final gear was still only 11 teeth.

[FiatMac]

You can put an automatic rear end in the car which will drop rpm significantly but sacrifice lower end but being a turbo that will be less of an issue.

See the charts in my post in the thread below:
http://www.fiatspider.com/f08/viewtopic ... 17&t=19436

The 3.58 ratio automatic rear end will give a speed of approximately 66mph at 3000 rpm. Not a huge gain, and the automatic rear end is not that easy to come by,

[giuliot60]

Thanks Stan. Good diagrams. I guess I did get used to V8s and V6s. I know 4s are supposed to rev higher, but like someone in the older post mentioned, he was able to do 100 in the early 70s car, which I did with my '74 Spider when it was 5-6yrs old.

So I guess I have to focus on more HP, maybe I'll put the turbo back in

[fiat218]

Thanks Stan. Good diagrams. I guess I did get used to V8s and V6s. I know 4s are supposed to rev higher, but like someone in the older post mentioned, he was able to do 100 in the early 70s car, which I did with my '74 Spider when it was 5-6yrs old.

So I guess I have to focus on more HP, maybe I'll put the turbo back in

105 mph top speed in my 72 ,slow

[giuliot60]

I was looking at a Road & Track article from '81/'82 about the Turbo Spider, and they mention that the speedometer is correct at 30mph but is actually doing 56.5mph when it reads 60mph on the speedo. So whoever mentioned that discrepancy, they were correct. The '81 also has 3.90:1 ratio rear (which we all knew anyway), and revs at 3500 rpm at 60 mph according to the article (probably the actual 60 mph, which is worse that I thought), and revs at 6000rpm in 5th gear when hitting top speed of 104 mph. And mind you, that is with the turbo, which mine doesn't have anymore.

[mdrburchette]

So, where in the US can you run over 100 mph? My 72 has a 4:30 and the thing hums nicely around 4k rpm at 70mph. That's where it's the happiest. It seems to get a second breath around this range. It's just something you get used to. These engines are designed to run high rpms.

[fiat218]

So, where in the US can you run over 100 mph? My 72 has a 4:30 and the thing hums nicely around 4k rpm at 70mph. That's where it's the happiest. It seems to get a second breath around this range. It's just something you get used to. These engines are designed to run high rpms.

In north Dakota. Lol I drive 95 to 100 in my 72

[mdrburchette]

Legally? Cool.

[fiat218]

Legally? Cool.

no, not legally lol. u know what i meant

[spiderrey]

Back in 1980 I topped out at 108 in my 71. Cant remember if that was with the 1608 or 2 liter though. Had the auto rear end in my present car and hit 125 not topped out. The only reason I know this is my son was following me in my 03 silverado at the time and told me later. That rear end got sold and car has been sitting for a year waiting for me to clean up and reinstall original rear end.

[giuliot60]

Did you sell the rear because you were able to do 125 with it S-rey?