3:31 Gearing

[cliffy49]

Looking into the possibility of a new to me TV. I just looked at a 2012 F250 with a 6.7 and 3:31 gears.

What I would like to know is if anyone here tows with this set-up and how it works. I realize that 3:31s are not normally the ideal choice for towing but since this is a diesel, it may be different. I realize that 4:10s or 3:73s would be a better choice. Buying used you do not always have a choice of the perfect unit.

The truck appears to have towed since it does have what I guess are part of the mount for a fifth wheel hitch in the bed. Also it appears to have the tow package just not the best set of gears.

Not trying to start a feud as to what is best, just trying to get comments and advice on this set-up. Thanks in advance for all of the help.

[4x4ord]

Could the contradiation in my posts be on account of statements I made that were intended to be understood as sarcastic?

Yes we agree that with deeper gears more weight can be towed.

The weight of the hypothetical trailer I used in the example of a 3.55 srw towing against a f450 was a 15000 lb trailer.

I am trying to point out that for lighter RVs such as a 15000 lb RV there is no advantage to deeper rear gears.

The theoretical story of the f350 srw being able to slightly out pull a f450 from 40 mph all the way to 70 mph with a 15000 lb rv in tow on any grade from level to 7% serves to demonstrate that fact.

[Grit_dog]

4x4ord wrote:
I think Grit Dog figured it out.... you have a different idea of what "better" means than I do. Do you honestly think that a new Powerstroke towing a 6000 lb RV through 4.30 gears will tow better than if that same truck had 3.31 gears? If so I would really like to know how you define "better"? Why do you suppose Ram and Ford offer these different gears if they could simply put 5.80 gears in all their trucks and have the "best" ratio for towing anything?

No, I think you could tow that figurative trailer that your using for an example with one of Robertryans Austrailain wonder trucks.

You've contradicted yourself enough in this thread to last a lifetime. We get it.. You can tow a little with a lot of power and a shorter final drive ratio. That's not news.
BUT you can tow MORE with the same power and deeper gears. Not news either.

[4x4ord]

dodge guy wrote:
If I was in the 450 I would just let you go on your way and stay back. I would hate it if you kept looking over at my trucks dash board at 50+ mph!

How do you know what I'm looking at?

[dodge_guy]

If I was in the 450 I would just let you go on your way and stay back. I would hate it if you kept looking over at my trucks dash board at 50+ mph!

[4x4ord]

I'm going to go at this only this one last time. I've got 3.55 gears and 20" wheels. If I'm towing my little rv down the highway at 65 mph I know the engine needs to produce roughly 130 HP.
I have the option of locking out one or both my overdrive gears. So I can run the engine at:
2620 rpm in 4th
1960 rpm in 5th
1525 rpm in 6th

Lower gears are always better so I should have gotten an f450 with 4.30 gears but at least I have the option of locking out both overdrive gears to make things easiest on my truck. How many gears should I lock out?

Say I hit a 4% grade and my truck is holding 65 mph in 4th gear at 2620 rpm. I notice right beside me is an f450 pulling an identical trailer to mine. I do the math and discover he's going up this hill in 5th gear at 2570 rpm.
Now say the hill gets a little steeper oh boy the f450 is starting to loose speed so I back off the accelerator just a touch to slow down with him. At 50 mph the F450 downshifts and his engine revs to 2675 rpm, and he starts to accelerate. I floor it to try to keep up and my truck drops to third gear and I'm running at 2675 rpm....Now we are neck and neck both of us with our foot to the floor. We pass a sign on the side of the highway and it says 7% grade.

Should I say boy I wish I had bought an f450 or does the "best" gear ratio for towing depend on the weight of my trailer?

[Lynnmor]

4x4ord wrote:

Huntindog wrote:
First off, when one is into these big trucks... Fuel economy is a secondary consideration to performance for most.

Second, just looking at the highway cruising gear of the trannys performance, misses a lot.

I have changed a R&P or two lowering the gear ratio in each case.
It totally changes the personality of the vehicle. It accelerates better in EVERY gear, and the engine BRAKING is better as well.
In short it is like a totally different truck.

Certain components such as brakes, u joints and the tranny will live an easier life, likely resulting in lower long term repair costs

Cool....I guess I should start driving with my transfer case in low range.

It is quite clear now that your only purpose is to argue. I think that is the definition of a troll. And yes, you should never take YOUR truck out of low range and low gear.

[Huntindog]

4x4ord wrote:

Huntindog wrote:
First off, when one is into these big trucks... Fuel economy is a secondary consideration to performance for most.

Second, just looking at the highway cruising gear of the trannys performance, misses a lot.

I have changed a R&P or two lowering the gear ratio in each case.
It totally changes the personality of the vehicle. It accelerates better in EVERY gear, and the engine BRAKING is better as well.
In short it is like a totally different truck.

Certain components such as brakes, u joints and the tranny will live an easier life, likely resulting in lower long term repair costs

Cool....I guess I should start driving with my transfer case in low range.

Now that is just being silly. Most have a 2.62-1 low range. That would really change your effective ratio a lot. Too much to drive at highway speeds.
I have rebuilt a few of todays chain driven TCs as well. They are not really meant for constant use.

[4x4ord]

Huntindog wrote:
First off, when one is into these big trucks... Fuel economy is a secondary consideration to performance for most.

Second, just looking at the highway cruising gear of the trannys performance, misses a lot.

I have changed a R&P or two lowering the gear ratio in each case.
It totally changes the personality of the vehicle. It accelerates better in EVERY gear, and the engine BRAKING is better as well.
In short it is like a totally different truck.

Certain components such as brakes, u joints and the tranny will live an easier life, likely resulting in lower long term repair costs

Cool....I guess I should start driving with my transfer case in low range.

[Huntindog]

First off, when one is into these big trucks... Fuel economy is a secondary consideration to performance for most.

Second, just looking at the highway cruising gear of the trannys performance, misses a lot.

I have changed a R&P or two lowering the gear ratio in each case.
It totally changes the personality of the vehicle. It accelerates better in EVERY gear, and the engine BRAKING is better as well.
In short it is like a totally different truck.

Certain components such as brakes, u joints and the tranny will live an easier life, likely resulting in lower long term repair costs

[4x4ord]

I think Grit Dog figured it out.... you have a different idea of what "better" means than I do. Do you honestly think that a new Powerstroke towing a 6000 lb RV through 4.30 gears will tow better than if that same truck had 3.31 gears? If so I would really like to know how you define "better"? Why do you suppose Ram and Ford offer these different gears if they could simply put 5.80 gears in all their trucks and have the "best" ratio for towing anything?

[dodge_guy]

4x4ord wrote:

Grit dog wrote:
^Haha, yeah maybe not the best saying to use when talking transmissions and gears! Lol
Either way, 4xford, the confusion is your interpretation of "best" compared to others'.
I understand what you're saying and you're talking "best" balance maybe between ultimate capability and unloaded economy.
But that does not negate that deeper gears will pull harder all other things considered. You can cherry pick when a taller gear will be in the powerband for a given speed and pull harder and compare that to a lower gear, but that does not consider the fact that as torque multiplication increases so does pulling power. Period.

I think we understand each other although I would say that even towing a light trailer (such as many RV's) at highway speeds a truck is only needing 130 hp. So, it is better to have the engine run at 1400 rpm, where it can easily make that power, than have it turn at 1800 rpm where it is capable of making 300 hp.

:S you just refuse to acknowledge that the lower gearing will tow better no matter what!

[4x4ord]

Lynnmor wrote:

4x4ord wrote:
Thanks for the translation. I agree that 3.31 will work just fine and in fact will work even better than a deeper ratio when towing lighter trailers.......That is why it is offered.

You still don't understand, the 3.31 gear is not "offered" it is one of two gears that Ford selects depending on tire size and several options. The only measurable increase in power is with the 3.55 and 18" wheels that are included with those few options. Either way, not worth several pages of banter for the small difference.

I think you're trying to say you agree with me but you still want to argue? Anyway I agree with you that the difference is small and the arguing is not worth it.

[4x4ord]

Grit dog wrote:
^Haha, yeah maybe not the best saying to use when talking transmissions and gears! Lol
Either way, 4xford, the confusion is your interpretation of "best" compared to others'.
I understand what you're saying and you're talking "best" balance maybe between ultimate capability and unloaded economy.
But that does not negate that deeper gears will pull harder all other things considered. You can cherry pick when a taller gear will be in the powerband for a given speed and pull harder and compare that to a lower gear, but that does not consider the fact that as torque multiplication increases so does pulling power. Period.

I think we understand each other although I would say that even towing a light trailer (such as many RV's) at highway speeds a truck is only needing 130 hp. So, it is better to have the engine run at 1400 rpm, where it can easily make that power, than have it turn at 1800 rpm where it is capable of making 300 hp.

[Lynnmor]

4x4ord wrote:
Thanks for the translation. I agree that 3.31 will work just fine and in fact will work even better than a deeper ratio when towing lighter trailers.......That is why it is offered.

You still don't understand, the 3.31 gear is not "offered" it is one of two gears that Ford selects depending on tire size and several options. The only measurable increase in power is with the 3.55 and 18" wheels that are included with those few options. Either way, not worth several pages of banter for the small difference.