which rear? '80 or '76?

[maytag]

So, it looks like I've got a decision to make.
I'm parting an '80, and using some of it on my '76 (including the 2l motor)

If I understand correctly, the '80 will have shorter gears (lower-numerically) in the rear than the '76.

I'm a little askeered that if I go to the '80 rear, I might find that I lack the acceleration that I'm enjoying right now. But on the other hand: I drove mine about 40 minutes on the freeeway the other day, and 5k rpm gets monotonous!

any of y'all have any experience you can share?

thanks!

[So Cal Mark]

I prefer the 76, and not only because it's a stronger diff. I like the 430 gears and buzzing down the fwy is just fine with me; these motors like high rpm and that's where they make power

[maytag]

...these motors like high rpm and that's where they make power

Well, in the case of myu particular motor at the moment: It's ALSO where they LEAK OIL!!!

[azygoustoyou]

Okay, I'll be looking for the answer here. I have one of each and would like to know which way to go.

[maytag]

interestingly; the '80 appears to be hub-centric capable, as well.

Mark: What ways would the '76 be stronger? what all changed?

and the gearing: you mentioned 4:30 on the '76. Am I remembering correctly that the '80 is a 3:20? is that correct? I mean, that is a SIGNIFICANT difference.

[So Cal Mark]

the late rear ends were 3.9 for a manual and 3.58 for an automatic

[maytag]

ok. thanks for the clarification. So, not quite as drastic as I had imagined.
So if I do the math correctly: we're talking about a 10% difference in RPM/MPH.

so say, 4500K rpm instead of 5000. which is a big deal... but maybe not as big a deal as the lost 'pep' at the go pedal. ??

[So Cal Mark]

depending on tire diameter, 4500 is about 80mph with the 430 diff

[pope]

I have had both rear ends on my car and will tell you that you do notice the quicker acceleration of the old style pig. The new style is better at highway speed. The newer style is beefer in construction, in that the wheel axles are thicker and they bolt on to the housing where as the earlier versions were held on by spring c-clips.
The bolt-on pig of the earlier version is easier for maintainance.

I am back to the 78-on version and will stay that way, but its your call.

[maytag]

I have had both rear ends on my car and will tell you that you do notice the quicker acceleration of the old style pig. The new style is better at highway speed. The newer style is beefer in construction, in that the wheel axles are thicker and they bolt on to the housing where as the earlier versions were held on by spring c-clips.
The bolt off pig is of the earlier version is easier for maintainance.

I am back to the 78-on version and will stay that way, but its your call.

Pope: how do you use your car? And what HP mods have you done?

Here's where I'm at: I'd love to see as close to 150hp as I can, when I'm done with the motor. And while I'll drive it a couple times a week, it's primarily a toy. And will probably see a track-day or 4 every summer.
So honestly, I can't decide. Which seems to be my dilemma with a lot of things these days.

[mdrburchette]

The best of both worlds would be the 4:10 from a 70 model but they are being collected by the vintage and SCCA racers. This one would give you the performance range you are looking for. I'd rather have the lower end umph for track days or autocross and make sure the engine can handle higher rpms so I'll stick with my 4:30.

[MNspiderman]

stick with the 76 rear. Fiats are not high speed cars. So you might as well have a car that can take off and accelerate good.

[Mathew26]

Well I feel I need to throw my 2 cents in on this subject. This will be quick. As for which rear end to use....
I have seen a stock FI automatic car out run the 5 speed turbo cars. So I wouldn't be so worried about the acceleration of your rear end as I feel the cars can always make up for that. My suggestion is go with the 390 out of your '80. Unless you live in the mountains I think you'll be happier this way.

[pope]

Maytag,
Just wild, mild, street use and its stock F.I.

[spiderrey]

I had a stock automatic car, and I didnt feel I could out run anything.