Ford F-250 7.3 Gas Engine Axle Ratios

dodge guy wrote:

Hannibal wrote:
We just returned from a trip with our F-250 FX4 7.3L 10spd 3.55 towing our TT in sig. More than plenty of power. Backing into the side yard through grass and soft ground with plenty of grunt just above idle. In 4 Lo, I have to ride the brake. The only thing 4.30 gears would do is reduce fuel efficiency and make it sound like I needed another gear at the top end.

what gear is the truck running in at 65-70 both towing and non-towing?

Running empty, it shifts to 10th at 50~mph to run 1200~rpm. Towing 60mph, it likes 8th. I don’t know yet if it’ll shift to 9th or 10th towing 65-70. Traffic is thick in central Florida and, with Covid, we haven’t been out much or for very far.

Does tow mode automatically lock out 9 and 10, or do you force it to do that? Still towing in OD, not bad!

dodge guy wrote:

Hannibal wrote:
We just returned from a trip with our F-250 FX4 7.3L 10spd 3.55 towing our TT in sig. More than plenty of power. Backing into the side yard through grass and soft ground with plenty of grunt just above idle. In 4 Lo, I have to ride the brake. The only thing 4.30 gears would do is reduce fuel efficiency and make it sound like I needed another gear at the top end.

what gear is the truck running in at 65-70 both towing and non-towing?

Non towing at 65-70 will always be in 10th gear unless of course the engine needs to work to climb grade.
My 7.3 3.55 is at 1600 RPMS at 70 mph.

In tow mode, 9-10 are locked out and every gear is used on take off regardless of demand, no gear skipping like running empty.

Hannibal wrote:
We just returned from a trip with our F-250 FX4 7.3L 10spd 3.55 towing our TT in sig. More than plenty of power. Backing into the side yard through grass and soft ground with plenty of grunt just above idle. In 4 Lo, I have to ride the brake. The only thing 4.30 gears would do is reduce fuel efficiency and make it sound like I needed another gear at the top end.

what gear is the truck running in at 65-70 both towing and non-towing?

We just returned from a trip with our F-250 FX4 7.3L 10spd 3.55 towing our TT in sig. More than plenty of power. Backing into the side yard through grass and soft ground with plenty of grunt just above idle. In 4 Lo, I have to ride the brake. The only thing 4.30 gears would do is reduce fuel efficiency and make it sound like I needed another gear at the top end.

mich800 wrote:
There seems to be a common misconception about these higher gear transmissions. People seem to think these transmissions row through every gear sequentially under all circumstances. The big advantage is the ability to use different gear patterns based on load requirements. It is not just the bookend gears that make the difference. It is the ability to maximize fuel economy and performance under widely different acceleration and load scenarios.

Only the GM/Ford 10 speed and ZF/Chrysler 9 spds skip ratios. The 8HP70 ZF based Chrysler does go through every gear sequentially, even light throttle empty.

I think we're both making the same point (correct me if I'm wrong), which is when every gear ratio is used on a 10 spd, the rear end ratio becomes irrelevant. Except starting out from a dead stop as I mentioned above.

dodge guy wrote:
If that’s the case then why do the manuf’s offer different ratios. I know for a fact that a few hundred RPM makes a difference when towing. 300 lower in one gear can really help.

For starting out on a hill, or "startability" in towing industry. Also the reason why an equal horsepower diesel has significantly higher towing capacity, they have more than double the startability of a gas.

"Gradability" is what I was talking about, the ability to maintain speed climbing a hill. That's where gear ratios does not matter with 8 / 10 spds.

With 4 speed auto, it was a huge deal. If you couldn't make a grade in 2nd, you'd be crawling along @ 30 mph in 1st...

mich800 wrote:

RoyJ wrote:

dodge guy wrote:

kellem wrote:

dodge guy wrote:

kellem wrote:
Bought my 7.3 gas strictly for towing our 30 ft trailer and the 3.55 gears doesn't acknowledge a trailer is in tow.

4.30, 3.73, 3.55....10spd makes them feel the same.
Tremor sitting on 35" tires, maybe 4.30 is justified. Imo

But how do you know different gears won't make a difference towing your trailer?

It would be marginal towing at only half the trucks capacity.

Exactly! But if towing more weight that’s when the deeper gears make a difference!

With 8 / 10 spd transmissions, the only places it makes a difference is starting out in 1st, and ability to use top gear.

Other than that, in gears 2 - 9, with such close ratio, there's enough overlap your towing experience is identical.

i.e. the 4.30 truck in 6th would be within a few hundred rpm of a 3.55 truck in 5th, and a given road speed.

There seems to be a common misconception about these higher gear transmissions. People seem to think these transmissions row through every gear sequentially under all circumstances. The big advantage is the ability to use different gear patterns based on load requirements. It is not just the bookend gears that make the difference. It is the ability to maximize fuel economy and performance under widely different acceleration and load scenarios.

I agree, with Chryslers 8 and 9 speed transmissions you will never use all the gears. In fact the 9 speed trans in the Cherokee withnthe 3.2 V-6 doesn't even use first gear in normal driving, and you will never see 8 and 9 unless you get the car up to 90-100-120mph! First gear is only used when you put the 4WD shift dial in low gear, then it will use Frits gear in the transmission as your low range. Knowing the ins and outs is why I still say deeper gears when towing heavy is still necessary with the new multi speed transmissions.

RoyJ wrote:

dodge guy wrote:

kellem wrote:

dodge guy wrote:

kellem wrote:
Bought my 7.3 gas strictly for towing our 30 ft trailer and the 3.55 gears doesn't acknowledge a trailer is in tow.

4.30, 3.73, 3.55....10spd makes them feel the same.
Tremor sitting on 35" tires, maybe 4.30 is justified. Imo

But how do you know different gears won't make a difference towing your trailer?

It would be marginal towing at only half the trucks capacity.

Exactly! But if towing more weight that’s when the deeper gears make a difference!

With 8 / 10 spd transmissions, the only places it makes a difference is starting out in 1st, and ability to use top gear.

Other than that, in gears 2 - 9, with such close ratio, there's enough overlap your towing experience is identical.

i.e. the 4.30 truck in 6th would be within a few hundred rpm of a 3.55 truck in 5th, and a given road speed.

There seems to be a common misconception about these higher gear transmissions. People seem to think these transmissions row through every gear sequentially under all circumstances. The big advantage is the ability to use different gear patterns based on load requirements. It is not just the bookend gears that make the difference. It is the ability to maximize fuel economy and performance under widely different acceleration and load scenarios.

lenr wrote:
My opinion--yours will vary: Ford reference only.
Back in the days of the 4R100 transmission with its first gear ratio of 2.71 launch was a problem. When Ford came out with the 5R110 they split the old 1st into 2 ratios with the top 3 gears staying the same ratio. With a new 1st gear of 3.09 launch was improved. The 6R140 went to 3.97; more improvement. The 10R140 uses a 4.615 ratio. It is hard for me to believe that launch would be a problem with any axle ratio.

It is not a problem. But the point is, while 10 gear ratios can make up for a lot in final drive ratio difference, it is still easier on the drivetrain, more efficient and less stress with the gear reduction happening in the finals.
Will the new drivetrains handle it with taller gears? Appears so. GM doesn’t even offer anything deeper than a 3.42 on any diesels now. But that doesn’t change physics and to each their own how they choose to spend their money.
If I’m buying an expensive new gasser truck that doesn’t get good fuel mileage empty (comparatively) anyways, I’d skip and buy a diesel, but short of that, I’d get the deep gears and get my money’s worth in performance out of the truck.