What set helps gas mileage the most

[Incommando]

Hi Bulldog,


I got 23 mpg with jeep truck in 70s and my CJ gets 23 mpg hwy now... Had 3.54 gears with 3 spd on T-18 (4th is granny)

Wow...I must have an odd-ball because on my T-18 FIRST gear is the granny...

Such simple mods equal doubling your MPG ( I have owned numerous FSJ's & CJ's) ? Wonder exactly why the factory didn't do it that way?

 

[MN CJ7]

Wow...I must have an odd-ball because on my T-18 FIRST gear is the granny...

Such simple mods equal doubling your MPG ( I have owned numerous FSJ's & CJ's) ? Wonder exactly why the factory didn't do it that way?

Not sure what your post is saying....

My POINT is the T18s are road driven like a 3 speed Transmission

Unless you have propeller axle gears like 2.72, granny gear is not used on pavement. ALOT of CJs do have way too tall of axle gear with tall tires.

Further, If I can get decent mileage with a 3 gears on the road, many CJs have 4 speeds like 176, some have Overdrive , and some even have 5 speeds that are used on the roads.... Tires, Transmission , Axles all need to match in a "range" for proper operation...... even that "range" can be slanted to: torque or mileage...

I guess if this level of success was SIMPLE we would all have it... Its a 35 year old system that can be tweeked or you can be happy with 10 mpg or like my jeep was single digits when I first got it.

Hard to Polish a Turd.....or no reason to polish a turd, waste of money & time.
If you have 190K on a engine and poor compression.... why try to trick it out.... That is why we ask for back ground info on jeep and worker/owner capabilities and even tools avail... Then we pick a game plane....

Now if you have some tech to offer would love to hear it.

Hope that helps you out some.

 

[Incommando]

Not sure what your post is saying....

My POINT is the T18s are road driven like a 3 speed Transmission

Unless you have propeller axle gears like 2.72, granny gear is not used on pavement. ALOT of CJs do have way too tall of axle gear with tall tires.

Further, If I can get decent mileage with a 3 gears on the road, many CJs have 4 speeds like 176, some have Overdrive , and some even have 5 speeds that are used on the roads.... Tires, Transmission , Axles all need to match in a "range" for proper operation...... even that "range" can be slanted to: torque or mileage...

I guess if this level of success was SIMPLE we would all have it... Its a 35 year old system that can be tweeked or you can be happy with 10 mpg or like my jeep was single digits when I first got it.

Hard to Polish a Turd.....or no reason to polish a turd, waste of money & time.
If you have 190K on a engine and poor compression.... why try to trick it out.... That is why we ask for back ground info on jeep and worker/owner capabilities and even tools avail... Then we pick a game plane....

Now if you have some tech to offer would love to hear it.

Hope that helps you out some.

I was joking when I pointed out that you called the 4th gear on the T-18 the granny ( your words not mine) instead of 1st gear. That is what the little smiley is for... but from reading the posts I can see that there may well be a language barrier involved here.

My tech suggestions were listed previously. Extreme mileage increases are rarely repeatable by others following the same "recipe." Moderate increases often come at the expense of moderate to severe driveabilty issues that most people are not willing to tolerate ( in my post I refer to this as "other drivers are going to hate you." ) The on-road performance of a 33" tire/3.54 gear ratio is one example of compromises some people are willing to live with while most folks think stink. The acceptability of a 28" tire and 3.54 gears is ok while the 33"/3.54 combo is often criticized for both poor performance and poor mileage. It would take going to 4.10's with 33's to equal the factory performance with 28's/3.54's. The RPM at 65, for example, is 2761 in the stock configuration and 2713 for the 33/4.10 combo. They remain very similar throughout the RPM range. Going even 3.73's and 33's actually numerically lowers the final drive ratio over the stock set-up, causing lower RPM's than stock at a given speed, not higher. Putting higher numerical gears in to compensate for an increase in tire size generally returns you to stock performance ( depending on ratios chosen) not super performance be it in speed or efficiency.

Folks with questions about tire size vs. gear ratio and RPM at a given speed should try this site Grimm Jeeper and play with actual numbers for a realistic look at what specific changes will do.

 

[MN CJ7]

Incommando,

I do not know you, nor have I shared threads and help with.... so I think your joking and miss quote is not proper.... The paragraph reads like this and was same info you just repeated......

I was also invited to help by the poster...

Hi Bulldog,

Saw you tried to send a PM, sorry I just leave it full, and stay on the forum pages for the most part.... Please tell us more about your capabilities??? and what you can do mechanicly? and have you worked on cars/jeeps in the past... Please tell us more about your CJ, how well is it running, miles on it, compression test, overall health, pictures....




I got 23 mpg with jeep truck in 70s and my CJ gets 23 mpg hwy now... Had 3.54 gears with 3 spd on T-18 (4th is granny) and I changed to 3.73 and less lugging so now I can change to the 18r slot, and recurve my dist and rejet my carb to take advantage of my gear change..... It all works together..... 3.54 is right on the edge with 33" tires but it can be done.... 32" might be better. Driving with vac gauge after you work can teach you to drive for mpg MAX.. Changeing gears is expensive and i did not do, had shop do it. I also had front ring gear with 2 theeth damaged, wanted lockers ft/rear and wanted 3.73 or 4.10 gears. Granny gear allowed me to go 3.73 and still have some low gears for off road.... my hyw mileage is excellent...but i tweeked pretty good see bio...

I used the word 3 speed with the 4th gear being granny, never said 4th was granny. Actualy the R on T-18 does change on different versions...

The poster has 3.54 gears most likely..... only going to cost $1000 for each axle to change the ratio.... So unlikely Poster is going to change the gear ratios. Still much better than the 2.72 or 3.33 gears that are pretty common in the CJs.

This is a new engine, tweeked, few can run like this... 3.54 gears and 33" tires I would not call this a dog or lacking in power.... By the way in the 2nd gear at 4400 rpms that was like 60 miles per hour in second gear of the ROAD 3 speed with granny being the 1st gear, starting in 2nd and using 2,3,4 as the road gears..... have to be careful not to confuse comando. I never use these Stock stuff except MSD CDI, Borla Header, Weber Carb, 80s alumium Jeep Intake, stock cam, lifter, rockers, hardened valve seats. My speedo is like 15 mile per hour off at the hwy speeds, so you will have to use grim or similar.

Jeep Main Album :: Working Gears II video by fjguercio - Photobucket

see if this works?

My Jeep is a peppy as my buds with a FI 4.0 and 5 speed.... they were very similar... so it can be done.....

 

[Petescj]

Just a reminder to keep it civil guys.