I am planning on working on my rear axle and differential as soon as I get a short time off.
Any ideas on how to improve it? Should I replace it with another 76 differential or should I look for another year that provides a better ratio?
Differential improvements for a 76
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baltobernie
- Patron 2020
- Posts: 3466
- Joined: Sun Nov 25, 2007 6:00 pm
- Your car is a: 1973 Spider [sold]
- Location: Baltimore, MD
Re: Differential improvements for a 76
What do you mean by "better"? If your '76 has its full compliment of smog equipment, you probably will want to stick with the OE axle, a 4.33 ratio. In 1978, Fiat changed the rear axle ratio from 4:33 to 3:90, probably to satisfy the owners in its biggest market, North America. This higher ratio delivers less acceleration, but improved fuel mileage and less wear-and-tear on the highway. Before doing anything, you should measure or identify what you've got in the car now, as many (most?) Spiders have had major surgery sometime in their lifetimes. Here is a 10/39 rear, with a 3.90 ratio.
If you have a 4.33, you'll see 10/43 here. If you have enough engine power, you can pull a 3.90 ratio and get a smoother, quieter highway ride without a noticeable change in performance. The speedo gear on the outside of the transmission must match the rear axle ratio, or your speedometer and odometer will be off. You may also need to change the panhard and/or rear link bars, depending on what's in there now.
If you have a 4.33, you'll see 10/43 here. If you have enough engine power, you can pull a 3.90 ratio and get a smoother, quieter highway ride without a noticeable change in performance. The speedo gear on the outside of the transmission must match the rear axle ratio, or your speedometer and odometer will be off. You may also need to change the panhard and/or rear link bars, depending on what's in there now.