Overdrive or Taller Gears for Fuel Savings

[MChildress]

My 1983 Ford 6. 9 diesel came with a 3. 08 gear 4 SPD. That thing would top out at 75 in third and the RPMS would not max out in fourth at over 100 mph. I pulled a 24 ft x3 axle gooseneck with it and never had any problems on the flat ground around here. I'm just wondering how high a gear these engines will push with the horse power we have now.

 

[Jrissler]

Same here. I have a ole 6. 9 with a 4 spd. and it would top at 100mph in 4th. was great. Why do they put more power out and then slow the rears down?? Thats why they give you 6 gears to chose from.

Is it suppose be cool that you can say that you can pull every hill in high gear?? Yea I agree that toppin the hill in high is cool but not just because it has a high gear that does about 25 mph wide open!!! did I under estimate that speed just a lil??



A lil story about my 01 and my bro-in-laws 02. trucks are the same except his had 4:10 and my has 3:55 rears. both were stock at the time and we both had small 16' trailer behind I was pullin about 3000 lbs. and he was pullin about 1000 lbs. got to the big hill and I dropped mine into 5th and let the big dogs run but with the speed we were runnin he could not yet drop out of 6th so he had to stay in 6th and I came out around him and got out ahead of him pretty good. Was the same on every hill, I would drop a gear and pull away from him.



Moral of the story?? How come do they think that slower gears are made for towing?? I know you do need low gears for takin off, but can't they still give us a good high gear?? If I need lower gears I have a lil lever on the floor that will give 6 low low gears in that case.



Off my purch!!!! I shut up now!!!

 

[Jrissler]

Man I got 13 mpg coming in from OH last night, Maybe it will get better!!!!

 

[Bernie]

Wel, it looks like I will wait ...

I got an e-mail back from AAM today:



Your interest in AAM product is much appreciated. AAM will have a 3. 42 ratio available for your vehicle in early 2007. All AAM differential components are available through qualified distributors.



You can contact me in early 2007 for update regarding 3. 42 availability. In addition, you can contact our distributors for product. Let me know where you live and I will provide a distributor/s near you.



So, I will wait and try them when they become available. It won't be as great a drop as an overdrive, but it should cost a lot less. I can also keep my old gears. Should I hate it, I can change back.

 

[klenger]

I wonder if the new gears will require a new carrier housing. For the Dana axles, the carriers were different between the 3. 54 and 4. 10.

 

[ilovetrains]

At least you got a response. My email was viewed a week ago, but no response.

 

[JohnsonG]

I got an e-mail back from AAM today:



Your interest in AAM product is much appreciated. AAM will have a 3. 42 ratio available for your vehicle in early 2007. All AAM differential components are available through qualified distributors.



You can contact me in early 2007 for update regarding 3. 42 availability. In addition, you can contact our distributors for product. Let me know where you live and I will provide a distributor/s near you.

3. 42's... pick up . 31 over 3. 73... . around 8. 5% not sure if the change is worth the 8. 5 %... . Might be worth it if you had to replace bad gears...



Just hope we don't have to take out a second mortgage to get them...

 

[DPKetchum]

On my 93W250 I went from 3. 54? or 3. 55 to 4. 10s front and rear of course with OUT new carriers.

 

[Diesel Power]

not trying to steal the thread, but this is what has netted me and my customers best mpg on avg.

all amsoil fluids=3mpg@ 55

bigger tire 305 65 17=1 mpg @ 55

power enhancements=3-5mpg @ 55

built auto transmission=2mpg @ 55

i say 55mph because that was where i was able to do my best comparison and most consistent, i also have a 305hp 04'. everyones results will vary because of driving habits, but this is what i hear most from customers at this speed, some more than others. i personally have seen on my race truck a 5mpg increase from 18 to 23 on avg @ 55-60mph, i have the amsoil, power stuff, and the transmission--i still dont have the tires, but those who do report between . 5-1mpg. hope this helps

 

[klenger]

Adding up the above numbers, you are getting 8-10 MPG improvement with all the mods? Fuzzy math maybe.

 

[JHardwick]

I don't buy any of it. There are times towing heavy when I am sure I am getting better milegage with 4:10's and 6spd than 3:73 and an auto ... ... ... ... . way better! Even though I am spinning big revs! It all depends on what you bought a big truck for ... ... ... ... if you want to commute and get groceries, do the airplane gears ... ... ..... I'm just not into that "status thing".

 

[Bernie]

not trying to steal the thread, but this is what has netted me and my customers best mpg on avg.

all amsoil fluids=3mpg@ 55

bigger tire 305 65 17=1 mpg @ 55

power enhancements=3-5mpg @ 55

built auto transmission=2mpg @ 55

i say 55mph because that was where i was able to do my best comparison and most consistent, i also have a 305hp 04'. everyones results will vary because of driving habits, but this is what i hear most from customers at this speed, some more than others. i personally have seen on my race truck a 5mpg increase from 18 to 23 on avg @ 55-60mph, i have the amsoil, power stuff, and the transmission--i still dont have the tires, but those who do report between . 5-1mpg. hope this helps

The problem is, I care about real world driving, which means traveling at the speeds that the other vehicle around you are traveling. Traveling at 55 MPH on a 65 MPH road is unsafe. All of the traffic around you is moving 75 MPH, and to keep with the flow of traffic so should you.



And, what I don't get is when I add up all your numbers you are getting 9-12 MPG better than stock. That would mean your truck is getting about 25 to 28 MPG?



Not to mention, you have an auto trans. You have a taller final drive overall.

 

[Bernie]

I don't buy any of it. There are times towing heavy when I am sure I am getting better milegage with 4:10's and 6spd than 3:73 and an auto ... ... ... ... . way better! Even though I am spinning big revs! It all depends on what you bought a big truck for ... ... ... ... if you want to commute and get groceries, do the airplane gears ... ... ..... I'm just not into that "status thing".

Alright, I give. What do you mean by "airplane gears"?



I use my truck for work and for play (to tow my race car(s) around).



Work: I call on Fire Departments and sell them the equipment they need to do their job. Between carrying equipment for demonstrations, delivery, and service I often have heavy loads in the bed. My last truck was a Tundra, and I kept overloading it. Probably about 35k to 40k miles a year with use like this. You could call it "commuting" or getting "groceries", but the "groceries" I often carried overload a 1/2 ton pick up (not always, but enough to look at a 3/4 ton)



Play: I race just about any car I can get my hands on in just about any race series I can get to. These range from ice racing with my ice race car and trailer (combined at about 3000 lbs), to towing two cars on an open trailer to the Targa Newfoundland race (34' long, combined weight of about 11k lbs). This represents about 8k to 10k miles a year for me.



As you can see, I will give up some towing millage for economy the rest of the time. I also understand that going to 3. 42s will make the towing a little more work. However , at no time did I feel like I needed more power towing with the 3. 73s, so I am confident that going to the 3. 42s the towing will still be good.

 

[JasonCzerak]

The problem is, I care about real world driving, which means traveling at the speeds that the other vehicle around you are traveling. Traveling at 55 MPH on a 65 MPH road is unsafe. All of the traffic around you is moving 75 MPH, and to keep with the flow of traffic so should you.



And, what I don't get is when I add up all your numbers you are getting 9-12 MPG better than stock. That would mean your truck is getting about 25 to 28 MPG?



Not to mention, you have an auto trans. You have a taller final drive overall.

at 7200-7400#'s (fuel weight) @ 60mph I have hand calculated 25mpg. Juice on 1 or off (1 on one direction 0 on the other). EZ on 1.



it's not all that impossible to get to 25. Now factor in a smaller truck, short box for example.

 

[Bernie]

at 7200-7400#'s (fuel weight) @ 60mph I have hand calculated 25mpg. Juice on 1 or off (1 on one direction 0 on the other). EZ on 1.

Thanks, but again 60 MPH is not a real world driving speed. If you are driving 60 MPH on a highway that is moving 75 MPH, you are creating an unsafe condition. Being a rolling road block (and assuming everyone around you will adjust to you) is just as unsafe as the driver who is doing 90 MPH (on a road traveling 75 MPH) and assuming everyone around him/her will adjust to them.

 

[JasonCzerak]

Thanks, but again 60 MPH is not a real world driving speed. If you are driving 60 MPH on a highway that is moving 75 MPH, you are creating an unsafe condition. Being a rolling road block (and assuming everyone around you will adjust to you) is just as unsafe as the driver who is doing 90 MPH (on a road traveling 75 MPH) and assuming everyone around him/her will adjust to them.

HA! exactly. perfect. yep 100% agree! I rarely do 60. But where I can, and were I do have the time. I do 60.



Over all, I get 18-19 city/highway/boxes_set_on_kill_toying_around.



But it doesn't change the fact that if you do the speed limit, you can get good millage. But yes. If you feel you must go slower then traffic. You sure are retarded. You should be able to get tickets for going too slow...



But then again the cops around here, despite the big huge white and black signs "do no cross double white lines". don't pull people over for crossing them, right in front of cops..... Ever since my move to 6 miles from work, and never on the highway during 7-9am and 4-6pm. my stress levels have dropped alot

 

[Diesel Power]

The problem is, I care about real world driving, which means traveling at the speeds that the other vehicle around you are traveling. Traveling at 55 MPH on a 65 MPH road is unsafe. All of the traffic around you is moving 75 MPH, and to keep with the flow of traffic so should you.



And, what I don't get is when I add up all your numbers you are getting 9-12 MPG better than stock. That would mean your truck is getting about 25 to 28 MPG?



Not to mention, you have an auto trans. You have a taller final drive overall.

i hardly drive at 55 anymore eather but it was only for comparitive reasons and yes if you go from 18-23 you get a 5mpg increase, i did however once get 26mpg, but that was long time ago before they changed all the diesel fuels

 

[GeoffParker]

I have the Gear Vendor on my 2005 QC G56 6sp Dually... ... If you travel at 70mph or higher the GV is awesome for reducing RPM, noise and better fuel economy... ... . If you travel at speeds of 65mph on flat land you are okay using the GV but you are stressing the system when you drop below that... ... . The GV is not effective with the G56 transmission at splitting the lower gears as they are just all too close together... ... The only effective use is as a 6th overdrive, which is why I bought it.



If you get the GV call their corporate office in California and ask them who the best and most experienced installer is in your area... ... The guys at the corporate office know their stuff... ... . Also make sure whoever shortens your driveline is an expert... ... The way it is welded and balanced makes a huge difference in the drivability.



I had a horrible experience initially when Camping World in Wilsonville, OR installed mine almost a year ago... ... The installer goofed and hooked up one wire incorrectly that caused my automatic transfer case to engage and thus bind up when the GV unit was doing a self test... ... . That problem got solved after 3 trips back to Camping World.



The other problem was a shudder that would happen in first gear..... Camping World tried to tell me that the high torque of the Dodge was the problem when in fact the driveshaft was the real problem... ... . I ended up having a driveline shop I trusted redo the driveline and then had another shop they recommended do the install and alignment... ... After that shudder was gone and all is well.



I never tow with my GV engaged as I also have a PacBrake PBXR which I leave on all the time I'm not using the GV... ... The GV and exhaust brake cannot be used at the same time... ... . Also you can't engage 4wd when using the GV and it would be of no use anyway.



The GV is very spendy and don't expect to pay for it in fuel savings unless you keep your truck forever... ... Driving at high speeds over 70mph you will smile everytime you engage it!

 

[Lektrikman]

Overdrive or taller gears

Geoff, Thanks for the comments. Did you realize any change in mileage when running with the Gearvendors engaged? I am interested in an overdrive so I can cruise with the interstate traffic, which is seldom at 65 where the truck seems comfortable. My 05 CTD mileage seems to really drop off when cruising above say 65 mph, which is a bit unrealistic out on the "boulevard". Thanks again, Lektrikman

 

[GeoffParker]

I had the GV installed at 3,000 miles which was well before the engine had loosened up... ... . Now that I have the GV I use it whenever conditions allow..... Which really means I don't have any real way to compare before and after mileage... ... Mileage does suffer at higher speeds on these trucks as you are really working to push through the wind... ... The sweet spot on mine for maximum fuel economy is 55mph... ... . I have recently had my trucked flashed and the fuel economy on the computer has improved (not sure if that is actual or just hopeful)... ... Today at 70mph with the GV engaged it displayed 19-21mpg... ... . Don't buy the GV and expect to pay for it with fuel savings anytime soon... ... If you use it properly it will extend the life of your engine and transmission as they do turn fewer RPM's... ... If you run 65 or less with the GV engaged in 6th you are stressing the clutch and transmission..... Hope this helps.