Rear End Ratios

[Daniel]

I came across some notes on all the Ratios from early to late Spiders since people are always
talking about changing them around i thought of posting the info for everyone .

Ring & Pinion
12 x 39 = (3.58:1) only came with Automatics

10 x 39 = (3.90:1) 1978 - 1985 5 Speed Transmission

10 x 41 = (4.10:1) Mid 70s

10 x 43 = (4.30:1) Early 70s

9 x 40 = (4.44:1) Late 60s

[pleiades]

For that Automatic ratio, what years would that apply to?

Steven

[Ernie]

Daniel,

It's possible you have early and mid 70s reversed.

Regards,
Ernie

[Daniel]

Automatics first came out in 1979 .

About the Early and Mids you might be right i am sure some 1 will look it up and post a correction they always
do here .


Daniel

[pope]

: 1967-70 4.10:1 (1438 engine)
: 1971-78 4.30:1 (1592,1608,1756 engines)
: 1979-on 3.90:1 (1995 engine)
: 1979-on 3.58:1 (auto transmission)

The 4.44:1 only went in the sedan versions not the spider. The other problem is that people are replacing pinion gears from every year, so you may see gears in cars from other years. Kinda like cross breeding, you forget what the original was. Fiat also kinda crossed over the year line a little using the remaining gears in the next years model. Ex. some 4.1:1 were used in early 1971 and so on.

Hey Daniel..I miss the Bandit name you used to use.

[racydave]

Me too Bandit! Howbout gettin some taller tires?

[Daniel]

Hey Pope


I think the 1756 Super Brava in 1978 had 390s ? not sure 100% but thought it did come with that .

Yes Taller Tires will make the Gearing feel Taller if you can find anything ! but 13" stock size
tires are very hard to find last purchase i made of 13" Tires i had 1 size to select from i
didn't shop around . Taller would make the handling bad to much side wall flex it's amazing
how much tires can change the handling of a car . I try'd a few Tire sizes and brands in the past
it's amazing how much tires can change the feel of the car .


Signed Daniel AKA Bandit

[pleiades]

So here's another question then -what is the difference in a rear axle with a sealed rear diff cover VS. one that has a rear diff cover that is bolted on?

[Ernie]

It's my understanding that the spring perches are at different heights.

The radius rods are the same length. But, the panhard rod is different on early vs. late cars. I'm not sure what problem that might cause if you try to put a late axle assembly in an early car or vice versa, though.

Then, there's the problem with the speedo drive on the transmission. It's matched to the differential ratio. The speedometer will be out of whack if you don't change the drive gears.

Ernie

[pope]

Hey Bandit,

Super Bravas?.........What the heck do I know about Super Bravas. LOL I just know Spiders

[pleiades]

It's my understanding that the spring perches are at different heights.

The radius rods are the same length. But, the panhard rod is different on early vs. late cars. I'm not sure what problem that might cause if you try to put a late axle assembly in an early car or vice versa, though.

Then, there's the problem with the speedo drive on the transmission. It's matched to the differential ratio. The speedometer will be out of whack if you don't change the drive gears.

Ernie

That's helpful info - first I need to figure out which I have - Currently on my car is an axle with no bolt-on cover on the back. (it's an 81) - My '81 parts car has a bolt-on cover on back, so I'm confused about which one is the early rear-end and which one is the late rear-end.

That being said, which one has the higher spring perches?

[So Cal Mark]

the axle with the rear cover is the late one

[Daniel]

Super Bravas?.........What the heck do I know about Super Bravas. LOL I just know Spiders

Hey Pope

Super Brava's came out in 78 it was the cross over from the 131 1 series i think it was a USA only name
and it didn't last long in 79 the were just called Brava's besides they weren't all that "SUPER" anyways !
just a ADF Carb 1800 87 HP in stock form they were Super slow ? and didn't handle as good
as a spider !


Daniel

[pleiades]

the axle with the rear cover is the late one

Thanks Mark - I kind of guessed that was the case, as the images in my service manual seem to indicate that. Guess that helps explain my speedo being off and the car seeming to have VERY SHORT gears.

Steven