Successfully unsuccessful Neon gear swap

[grswat]

Greetings. I recently picked up a 96 Neon SOHC auto trans to use for running my 100 mile/day courier route and for me or my wife to drive when we are going somewhere solo. I had heard that there were some different transfer gears available for the 3 spd auto and did some research. I found that the Neon came with a 1.04:1 ratio and that a lot of late 80's Chrysler's had a .91:1 gear set. I was able to find an 87 Plymouth Horizon in the junkyard with that gear set and only paid $10 for the gears so at least my investment wasn't much. Prior to the gear swap I was getting 31-34 mpg. I did the swap and dropped my 70 mph rpm from 2900 to 2400 so I was expecting a good increase. I have filled up twice and got 31.9 and 32.9 so I didn't exactly gain anything. At the very least the engine isn't as noisy and screaming at highway speeds and the acceleration didn't seem to drop much. I predict that on a long highway run the increase would be much better.

[mcrews]

lowering rpms is always a good thing.

[Frank Lee]

I don't see a gas log, and it is winter. Two trips is not enough to pass judgement on the efficacy of this.

[Daox]

The temperature is fluxuating so much at this time of year to get any good numbers.

[ksa8907]

Does the speedometer read correctly or is it under reporting miles?

[arcosine]

Dropping from 2900 to 2400 without the gear swap would of had more of a gain! Which way the wind is blowing makes a 5 mpg difference on my car.

[Fat Charlie]

I'm with ksa8907. I don't know how that car calculates mileage, so I don't know if it's reporting the right numbers. How regular is your route, grswat? Is there a part that you know what your car always reads a certain distance, and is that the same?

[grswat]

I agree that 2 fuelups are not a for sure thing but was hoping for significant immediate improvement.

Yes the speedo/odo read correctly the gears are before the speed sensor.

My route is the same everyday, probably about 85 miles of interstate and 10 in town with very little traffic (at 4 am) but a dozen lights or so. I'm just dividing miles by gallons at fuel up to calculate.