Lower ratio 5th gear

[snakeknuckles]

So on paper here it is (please check my math):
Ratios :
trans : 1-3.667, 2-2.1, 3-1.361, 4-1, 5-.881
rear wheel w3.90: 1-14.30, 2-8.19, 3-5.31, 4-3.9, 5-3.44
rear wheel w 3.56: 1-13.05, 2-7.48, 3-4.85, 4-3.56, 5-3.136

for 15" tire: od=22.5", 60 mph = 896rpm(wheel) = 3082 rpm(engine) w 3.90, 2804 rpm w 3.56

and w .78 fifth gear and 3.56 rear: 60 mph=2483 rpm, and 140mph =5804 rpm

With all that said, I will let you know how she performs with the 3.56 rear. I might wait for the dust to settle on my credit card before getting the new trans...

ps. do I have too much time on my hands?

[djape1977]

my 2 cents

fiat is not a lazy american v8
it's perfectly normal for it to be driven at constant 4-5k rpm

being a drop top, 124 spider is inherently noisy at high speed. by installing a tall ratio rear end you're robbing it of it's best part - short bursts of acceleration and nimble handling on curvy roads. whatever you do to it, it's never going to be a silent high speed cruiser.

[RRoller123]

I get that, but we don't use 5th for short bursts of acceleration on curvy roads. That is for 4th.

[snakeknuckles]

... or 3rd

[snakeknuckles]

So it took me about 6 hr to complete the swap... The diff I got from Bayless seems to be in excellent condition and has the 43/12 ring and pinion. I just drove it around town and so far I am pleased. no perceivable loss in acceleration from stop, cruising 65mph shows 3000 rpm. Just have to relcalibrate speedo now...

[djape1977]

then you must have 300hp engine if there is no loss in acceleration.

[snakeknuckles]

Serbian water must be intoxicating...

[djape1977]

if you're willing to talk about water, how is your water supply? tested for lead recently???

[snakeknuckles]

Whoa... Sorry to drift off topic. I was looking for a polite way to say you are wrong about the performance of a 2l 120hp motor that red lines in the mid 5ks... Don't get me wrong, the 3.56 rear does not make a major change in drivability, but I think it helps. I still haven't put a ton of miles on the car since the switch, but I do think the lower gears are much more useful in town now and the 3000 rpm/65mph cruising is much nicer than 3300. I still plan on some day going for the .78 5th gear as well.
ps. I am waiting for a speedo adapter (Clark Bros aa 10888) which should correct speedo.-I hope I can make that work

[pdx124]

ANother option is to put in a 131 gearbox. I think they have a lower OD ratio.

[fiatfactory]

.