Changing final drive ratio in automatic, possible?

[PandaBear]

The corolla got such a low MPG (26-29) because of the 3spd auto despite the 1.6L engine, I want to change the gear ratio to improve the economy. Other than switching to a larger diameter tire size that will clear the front, I don't know what else I can do. Any suggestion other than selling it and get another car?

 

[Mr Nice]

I'm sure you can, but it would be expensive to take the trans apart and put it back together.

If it was rear wheel drive, you could simply swap the ring and pinion for around $200

 

[Steve S]

Originally Posted By: LT4 Vette
I'm sure you can, but it would be expensive to take the trans apart and put it back together.

If it was rear wheel drive, you could simply swap the ring and pinion for around $200
parts +labor???

 

[Steve S]

If there was parts for the ratio change you would never see a payback for the job. How much can you get for your car for a trade in or private party? What will a new car cost + license cost you per month? Will you see enough of a savings in your present gas bill to pay for your new car plus its gas bill?

 

[Mr Nice]

Quote:
parts +labor???


$50 for used ring and pinion.....$150 for the labor for a rear wheel drive car.



I agree, you would never recoup your money with that Auto trans due to the cost.

If he really wants to save $$$ on gas, I would sell the 3speed Auto Corolla and find a 5 speed Civic DX or Corolla.

My wifes 1998 Civic (5 speed) easily got 36 city and 41 highway tank after tank.

 

[Steve S]

I would guess it is a fwd.If it were a rear wheel Corolla I would keep it.

 

[eljefino]

Find out if the trans case is the same between stick and auto versions. If so the differential may swap.

Also some FWD ATs have a chain drive; one may have a 33 and 37 cog units on either end that could be swapped. This is more commonly possible on, say, a GM 4t60 that handles a wide variety of weight vehicles.

Personally I would do a 5-speed stick shift swap on the corrolla. The computer won't mind as the 3-speed is all mechanical anyway (except for TCC).

That 3-speed in corrollas/prisms, as well as the versions they dumped in neon expressos and value line cavaliers, are the worst jokes on so-called "economy" cars. Suprised/ashamed CAFE didn't force (subsidize) 4 speeds in them.

IIRC, the chevette had a 4 speed back in the early 80s.

 

[MrCritical]

The engine doesn't have enough torque to support a higher drive ratio (lower numeric) I wouldn't think.

My 3 speed '92 Prizm never got less than 30. Wish I still had it.

 

[brianl703]

The Ford Escort got an electronically controlled 4-speed automatic in 1991. Along with a distributorless ignition and an independent rear suspension. All stuff that many other economy cars did not get for several years after that.

 

[eljefino]

The corolla wagon got a 4 speed auto as well as 1.8 liters instead of 1.6.

To swap this over would be pretty major surgery.

 

[Tosh]

Originally Posted By: Steve S
If there was parts for the ratio change you would never see a payback for the job.

That was also my first reaction. But then I did the math:
27MPG = .037gal/mile; Fuel cost: $4/gal x .037gal/mile = $.15/mile
40MPG = .025gal/mile; Fuel cost: $4/gal x .025gal/mile = $.10/mile
Difference(savings) = $.050/mile

So, if the cost of conversion is $200, the number of miles to break even point is $200/$.050/mile = 4000 miles. For $2000, drive 40000 miles.

 

[tom slick]

you mileage wouldn't go up nearly 50% just from swaping gear ratios. you might go from 27MPG to 30MPG.

 

[Anduril]

Wife's 3-speed Cavalier gets 29 mpg highway. My 4-speed gets 31-32. Around town there isn't much difference, as the OD isn't used. Not worth the swap.

 

[PandaBear]

I wouldn't do a complete swap on this car. While the engine and transmission seems to be in good shape, the body, suspension, interiors are all starting to wear out. Heck, it is a 13 year old econo-box with 173k miles. I just though that there were simple part swap that I could do to save a few bucks (like maybe a bigger diameter tire size).

The car is FWD but with a separate front differential sump (very odd). My guess is that they used to have a 4WD version of the same transmission that they share parts with, hence easy to swap in a different gear ratio.

If I were to do a manual swap, I would do it on my Integra. At least it has a known and common procedure and the engine is fairly worn and even higher mileage (210k with a top end rebuild).