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Old 02-04-2009, 01:44 PM   #10 (permalink)
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Originally Posted by pfederighi View Post
Now on to transaxles again... What's the drivability like with a 3.52 transaxle with 13" wheels? Is it comparable to anything else on the road or that I've driven (the small cars I've driven are: '79 Mazda GLC, '80 VW diesel Rabbit, '83 Nissan Sentra, early '80s Plymouth Horizon automatic, early '90s Geo Metro automatic, '95 Geo Metro)?
The only way to truly figure that out is to run the numbers of those cars using an RPM/tire size/gear ratio/final drive calculator, and compare engine power.

Does anyone know the economy difference between an XFi with 13" wheels and a 3.52 with 13" wheels?
It'll be less than the 5.2% top gear steady state improvement I measured by going from stock to the 3.52 final drive. I don't know anyone else who has tried to systematically figure out the improvement from an XFi tranny swap, so the best you can do is estimate.

Would it be worth an extra $125 or should that money be saved and when my tires wear out (which may be a while since they're new), go to 14" rims and get close to the same effect?
Only you can answer that - do the calcs based on how much you drive, how much you reasonably expect to improve fuel economy (you can only estimate), and what you think fuel is going to cost in the future.

Also keep in mind that when you go to taller tires, you'll be increasing ground clearance and frontal area, which have aero penalties.

Also, would I possibly be hurting my economy by going to a 3.52 .. I imagine that with a 3.52 I would probably have to downshift to 3rd
Again, you can answer this definitively by using a calculator, eg:

Calulators from

And compare to what RPM you're currently using in 4th to get up those hills.
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