Thread: Rear end swap

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My 2 cents worth----I built a 27 T roadster with a 350/350 in it. It just didn't have tha punch that a car that light should have. I put a cam and a new 4 barrel in/on the 350 engine. ---better, but still 15 points short of awesome. Then I swapped out the rearend gears (they were 2.79:1 or 3.08:1)---nor sure which, for a set of 3.55:1 gears. GOOD LORD!!! WHAT A DIFFERENCE!!! It finally acted and felt like a hotrod. And the car still operated commendably at highway speeds.---Brian

Like Brian said ........

The 3:55's are a great all around set-up but work especially well on the street with lighter cars with a bit of torque as well. With 30" rear tires and 1:1 final drive the car will cruise 70 mph at 2,800 rpm. It turns out that for these types of cars with auto trans a perfromance converter is locking in right around there as well.

Kitz

No other modification gives you so much bang for your buck and seat of the pants feeling of performance as a gear swap to a lower ratio (higher numerically). Conversely, when we hot rodders put tall tires on the back to get that rubber rake or big and little look, it knocks performance way down.

The days of running 4:11's, 4:56, or 4:88 gear sets are pretty much gone as we now like to take our cars on the interstate and it is no fun turning 4 grand trying to keep up with traffic. So, as mentioned, gear sets in the 3:50, 3:55, 3:70-ish range are a good compromise, especially if you are running an overdrive tranny and/or tall tires.

My Kid just ordered 3:80's for the T he is building, but he is running 30 inch tires, and his cam doesn't come in until 2500, so it should be a workable ratio. I'm running 3:00 in mine also with a 30 inch tire, and might have to swap gears down the road once I drive it a little. My cam profile is much milder than his, so maybe my power band will be ok.


Don

My 34 currently has 2.73 ('81 Corvette) rear gears and while I have no problem with power and pickup, I admit 3.55 would be a treat, but only if I were to change out the trannny form a TH400 to a 700r4. With the current combo Th400/2.73 I get 10mpg around town and 15 hiway. If I would go to a 3.55 +/- I would probably have to change the trans to get the same or better mpg.

My wife has a Mountaineer which is AWD with the 5.0L engine and a 3.55 rear and on the hiway we average 21 mpg. For a vehicle that size with those components, that ain't bad.