Gear Ratios

[Smitty72]

Hey Forest River Techs,

Just wondering if anyone can give me a simple (if there is one) explanation of gear ratios for trucks. I know it affects towing capability. When looking for Tow Vehicles should I be looking for higher / lower numbers... and how much difference does it really make?


Happy Camper
Nova Scotia

[TURBS]

Higher gear ratio for towing.
Ie: instead of a 323 gear a 370 would be better.

TURBS
08 duramax tuned n modded, 32bhok Sabre
2015 camping "4 nights"

[OldCoot]

Bottom line, the bigger the number the lower the gear and the better for towing and worse for fuel mileage. A 4.10 is better for towing than a 3.23 or 3.70.

[Smitty72]

Ahh... ok... is there usually a price difference? and... how much difference would it make... say on a regular 1500 / 150 series pickup? A few hundred pounds or very significant... a couple of thousand?


Happy Camper
Nova Scotia

[OldCoot]

Originally Posted by Smitty72

Ahh... ok... is there usually a price difference? and... how much difference would it make... say on a regular 1500 / 150 series pickup? A few hundred pounds or very significant... a couple of thousand?
per
Nova Scotia

The lower gear will increase your towing capacity but not your load capacity.

[Happy Vibe]

There is a big difference. With my 2013 ram 1500 the 3.21 is around 7000lbs, the 3.55 is around 8600 and the 3.92 is around 10000. The price difference is not that much.

[Smitty72]

Originally Posted by OldCoot

The lower gear will increase your towing capacity but not your load capacity.

... meaning 'payload' what you can carry in the back...


Happy Camper
Nova Scotia

[Happy Vibe]

Yes changing your gear ratio will change your GCWR (the total weight of the Tv and trailer added together) but it will not change your GVWR ( the maximum your truck can weigh).

[Campster]

A higher number is a lower gear ratio...ie 4.10 are lower gears then 3.73. The lower gears reflect more pulling power from stop but worse milage from higher engine RPM....So I'm told.

[dustman_stx]

Which is "better" for towing is a little more complicated than is being made out here. The number is how many times the driveshaft has to turn over for the tires to make one complete revolution. The problem is that people attempt to directly tie that to engine performance, forgetting that there is another set of gears in play in the transmission. Back in the old 3 speed days when, to my knowledge, they all ran a 1:1 in drive- even with the old 4 speeds where 3rd was 1:1 and everyone's OD was very comparable- you could pretty much stick to the rule being presented here that lower is better. Not so much any more. For example- many Tundra owners think they've got one heck of a towing hoss on their hands because they have 4.30 gears. If you run the numbers, however, the overall drive ratio is almost identical to the new Ford trucks with the 3.73 gears because of the transmission ratios. Another thing to consider is where the torque curve of the engine lies. The lower an engine will produce torque, the higher the gear ratio can be (once again 3.55 is "higher" than 4.10) while still performing adequately. For example, the Ecoboost engine like I have produces torque much lower than a naturally aspirated vehicle. IMHO, there is absolutely no reason for anything over 3.73 gears in one- I personally think the 3.55's are low enough- and apparently Ford agrees as the 2015 models with the highest tow ratings have them. For a naturally aspirated V8, I would want 3.73's in a Ford ( I think Chevy too, but not real familiar with current offerings), 3.92 in the Dodge, or 4.30 in the Tundra for towing a heavy trailer. The new diesels have much higher gears than they did in the past as well- primarily because they have much more power and 6 speed trannies. The F250 6.7PSD now comes standard with 3.31's and can be upgraded to 3.55's. In 1997 you couldn't get any higher than 3.55 and everyone considered the 4.10's to be a must for towing heavy. Clear as mud now?

[OldCoot]

You could also get a 3 speed manual with overdrive, which took a 4.10 in high and when it shifted into overdrive down to a 2.88. Had a 55 Chev with it and a new 64 Chevelle with a 3 speed and od. You could re-wire the od to have shift into od at any speed in any forward gear.

[Jim34RL]

OK guys Ram throw that all out the window in 2013.5 with the introduction of the new Ram improved 6.7L Cummins Diesel trucks for the 2500 and 3500 models.


Any truck built after 2013.5 MY which was Jan 1 2015 introduction date that is a single wheel has only one gear ratio available 3:42 regardless of transmission. The maximum trailer weight for towing will vary slightly depending on options and cab style along with transmission selected. The gross vehicle weight rating is 10,000 LBS for the 2500 and the 3500 SWR will be around 11,100 LBS. Only the DRW trucks will offer different gear ratios for the differential.


Also starting in 2015 these trucks are all certified to meet the SAE J2807 towing requirements with the same differential offering as in 2013.5 MY; thus the SRW trucks have keep the 3:42 gear ratio as the only offering.

[Soonermikel]

I just bought a new Ram 1500 Hemi V8 with a 3.92 rear axel ratio…I'm pulling a 35 foot Wildwood (7,300 dry) and this was suggested for maximum towing. I've pulled it a couple of times up and down the Texas coast with no problems. Haven't had to go up many hills though...

[thebrakeman]

As far as cost, if different axle ratios were stand-alone options, they likely would be identical. They have to put in something, right? The cost comes in when you want to change axle ratios in your existing vehicle, involving parts and labor (or a straight axle swap).

Agree with dustman that it's not straightforward.
I've long noticed that the Ford Expedition can have the axle ratio changed from 3.55 to 3.73, and the max tow rating remain at 6000 lbs. Does not increase to 9000 until you add the HD Towing Package, which does not seem to include the axle ratio change.

[Smitty72]

Thanks Guys... I feel like I gave a better idea of the subject or at least know what to look for with regards to gear ratios.


Happy Camper
Nova Scotia

[V-Lite Fun]

I'm towing 6500# with a Ford Expidition 5.3 L V 8 and 3.31 gears. Works great around Florida and hilly areas. Haven't tackled a mountain with it. That might turn out to be a slow climb. I added an large additional tranny cooler that has a fan. Temps never get above 180 even in Florida heat. It seems to have plenty of power. The 3.73 would have been better but gas mileage would go down I'm sure.

[thebrakeman]

Originally Posted by V-Lite Fun

I'm towing 6500# with a Ford Expidition 5.3 L V 8 and 3.31 gears. Works great around Florida and hilly areas. Haven't tackled a mountain with it. That might turn out to be a slow climb. I added an large additional tranny cooler that has a fan. Temps never get above 180 even in Florida heat. It seems to have plenty of power. The 3.73 would have been better but gas mileage would go down I'm sure.

An "Expidition" with a "5.3L"???
Must be one of those cheap Chinese knock-offs!

V-Lite Fun,
Just joking around. We do that.
Welcome!

[dustman_stx]

Originally Posted by thebrakeman

An "Expidition" with a "5.3L"???
Must be one of those cheap Chinese knock-offs!

V-Lite Fun,
Just joking around. We do that.
Welcome!

Yeah. He's got a 5.4L.

[The Crow 1994]

Originally Posted by Smitty72

Ahh... ok... is there usually a price difference? and... how much difference would it make... say on a regular 1500 / 150 series pickup? A few hundred pounds or very significant... a couple of thousand?


Happy Camper
Nova Scotia

For Ram, going from the standard 3.21 to 3.92 in the 1500 class is a $50 option. Well worth it if you plan on towing with your truck.

[dustman_stx]

Originally Posted by The Crow 1994

For Ram, going from the standard 3.21 to 3.92 in the 1500 class is a $50 option. Well worth it if you plan on towing with your truck.

+1. Naturally aspirated engines need to rev higher to produce power and perform much better with lower gear ratios. That would definitely be $50 well spent.