Just got a 93 Escort GT to replace my 92 Protege DX

[GasSavers_Erik]

Looks like its time for a tranny swap!

I always thought that all things being equal, DOHC was a little worse for economy because you have more moving parts (more friction).

In the mid 80's Honda had 2 SOHC heads to choose from for their HF CRX's. They chose the 8 valve head rather than the 12 valve head.

I'd love to find a set of cheap roller rockers for my 87 Civic.

I worked on a 1999 Saturn with SOHC 1.9L and noticed that it had rollers built in to the bottoms of the hydraulic valve lifters.

[jj94auto]

What about this link here? Maybe there is hope.

http://www.pansypatrol.com/the-gas-mileage-mod/

[1cheap1]

Great post, I have a 95 Protege Lx 5 speed with 151k on the clock. At 65mph i am close to 3000 rpm, 62mph at 2700 rpm. At 24 to 2500 rpm going 57mph. With this info i should be able to lower the rpm in fifth. My 95 is a 1.5 sohc. Was thinking also to get coil overs to replace the struts and lower the car about 2 inches. My 89 240sx automatic in electric overdrive cruises at 65 mph at 2400 rpm. Changing the 5th gear is going to make me very happy!

[jj94auto]

Originally Posted by Erik

Looks like its time for a tranny swap!

I always thought that all things being equal, DOHC was a little worse for economy because you have more moving parts (more friction).

In the mid 80's Honda had 2 SOHC heads to choose from for their HF CRX's. They chose the 8 valve head rather than the 12 valve head.

I'd love to find a set of cheap roller rockers for my 87 Civic.

I worked on a 1999 Saturn with SOHC 1.9L and noticed that it had rollers built in to the bottoms of the hydraulic valve lifters.

Thanks...looks like we posted at the same time.

[jj94auto]

Originally Posted by 1cheap1

Great post, I have a 95 Protege Lx 5 speed with 151k on the clock. At 65mph i am close to 3000 rpm, 62mph at 2700 rpm. At 24 to 2500 rpm going 57mph. With this info i should be able to lower the rpm in fifth. My 95 is a 1.5 sohc. Was thinking also to get coil overs to replace the struts and lower the car about 2 inches. My 89 240sx automatic in electric overdrive cruises at 65 mph at 2400 rpm. Changing the 5th gear is going to make me very happy!

Yes, I have noticed your mazda before. Great numbers. I made my numbers over 1 gallon of gas in the city (with only 2 traffic stops though) and my wife and baby in the back.

Funny thing is, there were 2 quarts of lucas stabilizer in there and 2 quarts of 20w50.

What I don't understand is the final drive ratio?

If just the 5th gear is swapped, it won't effect the final drive ratio will it?

I have to swap the tranny as another posted stated.

Most of my commuting is in the city anyways. I drive 13 miles to a train station, and 13 miles back 5 days a week.

If you look at the gear ratios, I'll be better off in 1st and 2nd gear with the LX/Escort GT tranny anyways...it's just the 3rd and 4th gears that are shorter.

The 5th gear swap sounds great..heck I could pull it for free from my protege or get the even longer probe one.

I don't see how that is going to help me with my final drive ratio though or with my city driving.

However, I do like to get into 5th gear at as low an rpm as possible without lugging my engine.

Can someone help me out with understanding a final drive ratio in layman's terms?

Also, could someone let me know if I am on the right track with the lx\escorts 1st and 2nd gears being longer and better for fuel economy but worse in 3rd and 4th gears.

Can someone let me know if the longer 5th gear will balance this out...or is the fact that the final drive ratio is so much longer a fuel economy killer?

Thanks

[theholycow]

I'd also be interested in clarification on "final drive ratio". It seems to differ depending on who you ask.

Some people seem to think it's the ratio in the differential.

Others think it's the complete ratio between the crankshaft and the pavement in high gear. I always thought so until the last year or so when people have talked about it the other way. Obviously, for this definition of that phrase, changing out 5th gear for a taller one will change the final drive ratio.

[jj94auto]

Originally Posted by theholycow

I'd also be interested in clarification on "final drive ratio". It seems to differ depending on who you ask.

Some people seem to think it's the ratio in the differential.

Others think it's the complete ratio between the crankshaft and the pavement in high gear. I always thought so until the last year or so when people have talked about it the other way. Obviously, for this definition of that phrase, changing out 5th gear for a taller one will change the final drive ratio.

Yes that would be very useful.

Everyone seems to imply that its the ratio in the diff.

I hope that the latter applies!

[theholycow]

I can tell you this: Volkswagen uses the term "Final gear" to mean the differential. That much is for sure. From http://www.vw.com/rabbit/completespecs/en/us :
Transmission Gear Ratios:
1st: 3.78
2nd: 2.12
3rd: 1.36
4th: 1.03
5th: 0.77
Reverse: 3.60
Final I: 3.65

Note that it says "Final I"; this is because another similar model (the GTI) has a two-speed differential that has a different ratio for 5th and 6th gear than 1-4...crazy Germans.

Anyway, the issue is merely semantic. When you change your 5th gear, it doesn't change your differential, but it does change your RPM at a given speed in 5th gear -- so when you're cruising on the highway, you don't have to buzz along at a million RPM having run out of gears long before you ran out of torque.

[GasSavers_Erik]

IMHO- The "final drive" is the ratio of the differential gear set only. I can see how you would also calculate in the rest of the gear sets to get a "final drive ratio" for each gear that you are in. Most manuals give the ratio of the final drive only and then they also give the ratios of the individual gear sets. You can combine both figures to get the final drive ratio.

If you have all of the ratios (final and individual gear) and you know the stock tire size, you can figure the rpm in top gear at 60mph without even seeing the car.

[1cheap1]

94auto, i have found if you start off in traffic in 2nd gear then shift into 4th gear will help. If you travel the same route every day then map it out for the duration of the lights, then compare it to any alternate routes through residential side streets if any. The idea is to keep moving at any speed and avoid many stops. I do this in my home city. Changing that 5th gear does not look so hard. I will go to the junk yards where there are LOTS of Fords to choose from. In the last 2 years i have only found 1 95 protege.