Thread: Rear end swap

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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.

I put 3.73 in my '34. With the lower 1st gear in the 700R4, it gives me the same grunt as 4.56s behind an old Muncie. Then the overdrive gives me the equivalent of 2.61s in high gear.

I am running 2:90 something chevy and turn 2200 rpm @ 65 mph on the interstate. I get over 17 mpg and thats great but... The car doesn't really respond untill 3000 rpm, it takes that long for the motor to pull that car off the line. If I am doing 60 and stomp it, that sucker really comes alive but that sucks. It's boring sometimes!!!