Effective gear ratio stock tremor on 35’s?

[Evan_Carolina85]

I have very limited understanding of gear ratios but I am trying to wrap my mind around this scenario :

you buy a new 6.7 tremor stock with 35’s and 3.55 gear ratio , is the effective gear ratio 3.55?

you buy a stock 6.7 lariat with 3.55 gear and lift it and put 35’s on it , have you changed the effective gear ratio down to 3.31 or similar?

 

[Marley]

You are correct, gear ratio is factory.

But bigger engine displacement like 7.3 or 6.7 paired with 10sp tranny isn't nearly as affected compared to Jeeps I've lifted.

Jeeps almost always require a regear when going 35's or 37's.......not so much on these big trucks. Imo

 

[Evan_Carolina85]

You are correct, gear ratio is factory.

But bigger engine displacement like 7.3 or 6.7 paired with 10sp tranny isn't nearly as affected compared to Jeeps I've lifted.

Jeeps almost always require a regear when going 35's or 37's.......not so much on these big trucks. Imo

so would that mean that the actual gear in the tremor is a 3.73 and then after bigger tires than other models the effective gear ratio goes to 3.55?

or that stock tremors actually have a lower effective gear ratio than 3.55?

just not sure how a 3.55 gear in a tremor would be different than buying a lariat and adding 35’s on there? The effective gear ratio in the lariat would drop lower than 3.55 with the same size tires as the tremor. Maybe ????

 

[Treefiddy]

Tremors with diesel are 3:55 from the factory. No one regears these truck anymore including non tremors.

 

[Marley]

I've always lifted my trucks and went 35's and you will feel slightly less performance and visit the gas pump more often but physical appearance sometimes wins out.

You'll have no problem going to 35" tires on any of the Superduty trucks , not that much bigger than stock but it still won't be a Tremor.

If you tow heavy like I do then leaving it stock might be better option which is what drew me to the Tremor......factory lift, 35" tires, huge payload and towing capacity......for the win.

 

[Antimatterbluetremor]

I am pretty sure the gear ratio of 3.55 is the same in the tremor and the lariat, the only difference is the stock tire size, changing the tires does not change the gear ratio. If I understand correctly the lariat with 3.55 on stock tires and increased to the tremor 35" tires would effectively be the same.

Lariat + 3.55 gear + larger 35" tires = Tremor + 3.55 gear + stock 35" tires.

The stock Lariat with smaller size tires and a 3.55 gear ratio would be the difference in RPM of the tire at a certain engine RPM. The Engine RPM of 35" tires with 3.55 gears would be the same, Lariat or Tremor with the 6.7.

 

[Jman1428]

I have very limited understanding of gear ratios but I am trying to wrap my mind around this scenario :

you buy a new 6.7 tremor stock with 35’s and 3.55 gear ratio , is the effective gear ratio 3.55?

you buy a stock 6.7 lariat with 3.55 gear and lift it and put 35’s on it , have you changed the effective gear ratio down to 3.31 or similar?

The gear ratio pertains to the differential, how many revolutions of the driveline to how many revolutions of the axle, this does not change with tire size. Simple explanation would be 3 turns of the driveline make 1 turn of the axle ( 3:1 gear ratio ).

Now to tire size, simplified. 1 axle turn with 30" tire gets you 3 feet distance traveled. 1 axle turn with 35" tires gets you 4 feet distance traveled.

If you change your gear ratio to 4:1 (4 driveline turns to 1 axle turn) with 35" tires you will travel 3 feet.

So 3:1 with 30" tires will have the same power and acceleration as 4:1 with 35" tires.

These are not real numbers, just to show the idea. hope it helps.

 

[Pompey]

Adding 35” tyres will affect the overall gearing, regardless of existing diff ratio. However, adding the 35” or an other different sized tyres won’t appear on the advertised gearing you will normally see. You have to factor that in separately. However, with the Tremor package Ford factored in the tyres by making the 3.55 diff ratio the only one available with the 6.7.

 

[CalTremor2020]

When people talk about “effective gear ratios” what they are trying to do is find out, given two trucks that are otherwise equal (same engine, same transmission, etc.), what differential ratio would be required to make them move at the same speed when they are in the same transmission gear and at the same rpm. In this case that can be calculated by multiplying the gear ratio you want to compare by the difference in tire diameters (it’s actually circumference but the diameter works because math). Not sure how much of my work you want me to show but say you want to compare a tremor diesel (35s and 3.55) to a regular f250 diesel with the lower ratio (33s and 3.31) and you want to know, how much would I need to change the diff in the tremor so they run at the same rpm at 75 mph? We would do (35/33)*3.31=3.51. Interestingly, the lower diesel ratio f250 ends up being roughly equivalent (3.51 vs. 3.55) to the tremor with its larger tires. These trucks would run at roughly the same rpm at 75 mph and would exhibit similar acceleration performance (given wheel/tire combinations with equivalent grip and rotational inertia).

Getting back to your question, the tremor has an effective ratio of 3.31 when compared to a super duty diesel on 33s. Conversely, if you wanted to regear your tremor to perform like an f250 on 33s with the 3.55 rear, you would need to regear to 3.765.

If you are a masochist and would like to talk about final drive ratios, how much force is being put to the ground, peak torque, peak power, etc. you can message me. I could probably type here for a good hour

 

[Marley]

Hah, we got some mental heavyweights here. Lol

Here's a perspective from a caveman.
My last truck would see 2500 RPMS at 70 mph in OD stock.
Lifted with 35" Dynapro's, it fell to 2100 RPMS at 70 mph in OD.

So in my mind the effective gear ratio was.....effected.

 

[Junior2020]

At 3.55 to 3.31 the difference in RPM is almost negliable, the truck I traded in had 3.31 gear ratio, at 70 mph it was running around 50 rpm less than my tremor at the same speed. I am really happy with the 3.55, my 6.7 is getting 15.8 in town here and well over 20mpg on the freeway...towing the difference is all on the new motor...15k behind this truck and it does not even know it is there. My 17 had no issue's towing either, it had 3.31 ratio. I think the 3.31 would have more issue with the 35's than the 3.55 in the stock truck..just my opinion though...