2nd Gen Non-Engine/Transmission &th gear for 4:11 folks when empty

[richardleonard]

This is more of a wish that something real. . I really wish I could have a "7th gear OD" on my 4x4 CTD 6 speed to use during times I am not towing - daily runner to and from work... <SIGH> I get 17. 5 mpg around town and on trips unless I run at 70+ mph but at times envy the 3:54 folks and their 20 MPG,, specially since the cost of diesel is more than premium gas in this area of Virginia...

 

[Shovelhead]

Ask and Ye shall receive... ... ... ...



Gear Vendors Overdrive



Also check US Gear

 

[richardleonard]

Lets do the payback numbers

Lets see here,, roughly I am looking at spending approximatly $3500 plus or minus a few bucks to raise my fuel milage to lets say 21 mpg from 17. 5 mpg. . Given that fuel is now in the $1. 759 per gallon range in my area so over say 100 miles that would save me approximatly 1 gallon of fuel. . Then taking it one step more,, divide 3500 by the savings ($1. 759) per 100 miles,, it would come out to 1,000,000 miles to pay for this upgrade..... Am I being to anal about this??????? :--)

 

[Dkevdog]

This was kicked around quite a bit very recently here on the boards. If I can recall, the consensus was that the auxillary transmissions do not bring about the increase in mileage you are after. Save your money and buy the diesel fuel, or swap your rear end gears out to 3:54 or better yet, 3:73. Even if you can't find a swap and buy new, it is a fraction of what the auxillary trans will cost.



Kev

 

[richardleonard]

GRIN

After doing the numbers for the transmission it was very clear that was not the way to go,, even changing out differential gears would have a long pay back because I believe that cost was up wards of $1K or so...

 

[Koa Man]

Simplest way to get higher gearing is bigger tires.

 

[dremelts]

Originally posted by Dkevdog

This was kicked around quite a bit very recently here on the boards. If I can recall, the consensus was that the auxillary transmissions do not bring about the increase in mileage you are after.

Kev

Just to follow up on what Dkevdog said: the reason that you're not going to get the increase in mileage that the calculations say you should is because of the friction losses in the aux. gear box. Some of the power going into the aux. gear box is being used to generate heat which is just wasted energy.



The other arguement for the aux. gear box is its UNDER-drive capability so that you can save your clutch when backing your trailer into a campsite. But there too, you have to consider how much backing up you do and just how much you're taking off the life of the clutch when you do backup. You would probably have to save two clutch jobs over the lifetime of the aux. gear box for it to pay for itself. I don't think the savings add up in this case either.

 

[BigDan]

The only reason I would use the GV unit would be the higher top speeds.



With 4. 10's in 6th running 265's I top out at 103mph



If I had the GV unit I would top out at 133mph



If I had the GV unit with 315's I would top out at 145mph



I dont think there are any 315's rated for 145mph though



P. S just for fun



If I had 3. 54's gears GV unit 315's A/T my top speed would be 168mph. :--)



I might need an extra push out of the mighty cummins though, like some injectors and a turbo

 

[Shovelhead]

I agree that the cost savings won't be there.

But the cost/savings & up-front $$$ wasn't part of the 1st post.



Also if cost/savings was the bottom line we'd all probably be driving little electric cars. :{

 

[dremelts]

Originally posted by Shovelhead

But the cost/savings & up-front $$$ wasn't part of the 1st post.

I think cost savings was precisely what the 1st post was about: he was envious of the 3. 54 gear folks who are getting better mileage than he is.

 

[richardleonard]

Saving Money?? not likely in the short run

Yes, I am a bit envious of the 3:54 guys getting 20 plus or minus mpg but none of the solutions are without some down side. . the additional transmission or changing the gears are costly,, putting taller tires makes the speedodometer read incorrectly but does change the gear ratios and may give better fuel milage... It was a grand experment in thought anyway... I still get better fuel milage than the Dakota I had before my CTD and the CTD is about 3000 lbs heaver. . I was just thinking out loud that it would be nice to have a 7 gear OD for us 4:10 guys when we run empty...

 

[klenger]

From my expereince, the millage difference between the 3. 54's and the 4. 10's isn't anywhere near 3 MPG. Be carefull not to compare someone else's best milage to your average milage. Remember that the taller gears only help at highway speeds, and only when empty. I suspect the real difference is closer to 1 MPG depending on what your ratio of highway to city driving is.



I have been keeping track of total hours on my truck since new. I have about 23,000 miles and just short of 700 hours on it. That calculates to about 33 MPH average speed over the life of the vehicle. How much do you really think that my milage would improve by switching from 4. 10's to 3. 54's with an average speed of 33 MPH.



Also, I'm sure I get better milage towing (which is when you are using the most fuel) because I'm running in the "sweet spot" of about 2200 RPM. With 3. 54's I'd either be in 5th gear at about 2600 RPM or in 6th gear running over 70 MPH to keep the RPM's up.

 

[richardleonard]

Originally posted by klenger



Also, I'm sure I get better milage towing (which is when you are using the most fuel) because I'm running in the "sweet spot" of about 2200 RPM. With 3. 54's I'd either be in 5th gear at about 2600 RPM or in 6th gear running over 70 MPH to keep the RPM's up.

This is getting way out of hand,, sweet spot??? and now MPG comparisons... all this in response to me being envious of the 3:54 guys... Actually I wouldn't trade in my CTD 4:10s for anything,, I love being able to set cruise at 70 and not have it change for hills or anything else...

 

[Jumbo Jet]

No one calculated the residual value of the GV in considering the cost to own and operate.



I have a GV with 4. 10 gears and an automatic. The GV will help save the transmission - gives me a better gear ratio than the 3. 55 for cruising empty, and climbs hills like a mountain goat when I have my 8,000+ lb. trailer behind it. Mine only cost $2,100 - I installed it myself.



Best fuel mileage I've gotten so far was on a trip from Ontario, CA to Oklahoma City @ 79mph - 24. 5 mpg running empty with a bed cover on.



Otherwise, I get 21 or so running empty and average 17 around town without the GV engaged.



Running 65 to 70 mph with the trailer, I average 9 to 12 mpg according to how much head winds I encounter.

 

[richardleonard]

Cost of a GV

I looked at the cost - $2795. 00 for a CTD 4X4 as a bolt in. . still a looooong payback just based on fuel milage alone,, no I didn't figure in the additional residual value for resale - only operating costs...

 

[Dkevdog]

Any savings in "wear" on your standard transmission is null and voided by the fact that you now have a "second" transmission to maintain, repair and spin.



I agree with Ken than you shouldn't make MPG comparisons between trucks unless they are identically equipped and you are the one driving them. Driver influence is still by far the largest factor in mileage, and I'm somewhat skeptical of some of the mileage claims I've heard.



I am after a set of 3:55's not as much for mileage as I am for the other benefit- not running out of gear so fast. And for what it's worth, I have gotten better mileage out of the sweet spot than I have running in it, both empty and loaded.



Let the :-{} continue.



Kev

 

[rweis]

I have the 2002 3500 auto 3. 54 and will eventually pull a pretty heavy trailer.



Now pull 8k about once a month for about 200 miles one way.



The question I have is on the stress of 3. 54 vs 4. 10.



I put a Hytec cover on the diff last weekend and syn fluid. Looking at the gears to make sure they are meshing properly, and by the wear marks they are.



The internals (bearings, carriers) seem fairly substancial.



Just wondering what the difference in the stress level of towing heavy is to the diff.



As far as torque, with the 3. 54 I tow w/ O/D out about 65mph at about 2200 rpm. Stock transmission that will eventually go to an XXX rebuild / upgrade. Beefier transmission but same diff.



When I upgrade the hp from 235 to 350, beefier engine, same diff.



Should the diff be upgraded to a 4. 10 to handle heavier loads?



Thanks,



Bob Weis

 

[Dkevdog]

Bob- From another post about this whole gear ratio discussion, I quote from Rusty :

Yes, one can tow with a 3. 73 or a 3. 54, but for equivalent rear wheel torques, drivetrain torque loadings will be 9. 0% higher with the 3. 73 or 13. 7% higher with the 3. 54 than it is with the 4. 10's.



When you talk about towing a heavy trailer, how heavy?? If I remember correctly, the difference in GCVW rating between identically equipped trucks with the 3:54 to 4:10 is only 500lbs. Not enough for me to make a difference. I personally wouldn't be too concerned with the wear on the rear end from HP upgrades. Towing is hard on any rear end, but the Dana 80 on a 3500 is pretty stout.



Kev

 

[athompson]

Originally posted by richardleonard

I love being able to set cruise at 70 and not have it change for hills or anything else...

Me too! And I have 3. 55s with 315s! And I still hunt for 7th gear. Actually, I set the cruise at 80 and the only time I have to slow down is when the ricers get in the way.

 

[JBlock]

THe Trailer Towing difference is 2000 pound

Trailer Towing difference is 2000 pound on automatic (Dana 70), on a 2001 CTD 2500 4x4 the differnce in towing capacity is 2000 pounds 9xxx, verse 11,xxx for 3. 54 verse 4. 10 in Dana 70. I thought 3. 73 would be nice but based on the Dana 70 in the automatic you gain a 1,000 pound.



The real jump is to go with dana 80 like the six and five speed to get towing capacity. :-{}