I've been looking at new F350's SRW and everything I see has the 3:55 gearing. My intent was to get the 3:73 but apparently I would have to special order it. So my question is: How much am I actually giving up (uphill pulling) going to the 3:55 over the 3:73? The largest fiver we are considering is the Cedar Creek 36 CKTS, about 12K unloaded with a GVWR of 16.5K. If we get that particular one a dually would probably be a better fit and most of them on the lots have 3:73, I'm just not sure we are going to go that large. Is there a noticable difference between those two ratios when towing?I know its' a tough question to answer, so many variables, but just a general opinion or practical experience with these ratios would be helpful.

The general thought today seems to be that with the 6 or 8 speed transmissions the axle ratio is not as important as it was during the 3 or 4 speed tranny days.

You'll never notice it with 800+ft-lb of torque.

agesilaus wrote:The general thought today seems to be that with the 6 or 8 speed transmissions the axle ratio is not as important as it was during the 3 or 4 speed tranny days.I have 3.55 in my 01, with 5 speed manual. I do fine in hills with it but at 16,000# I think I would want the 3.73.If you have any thought of going big get the Dually now!

Hi,The rear axle ratio is picked out to give the best of both mileage, and performance. You will go up the hills a little faster when the engine RPM is higher, but get the best mileage at the lowest possible engine RPM.So with modern 6 speed transmissions, you use the 3.55:1 rear axle and shift out of overdrive while going up a steep hill at 55 MPH!I never really understood why anyone would want a 4.10:1 rear axle in a low RPM diesel truck. 3.55 is better. I had 3.73 with my 75 Ford and 3 speed, 460" engine. I would do around 2,500 RPM at 65 in drive, and 4,000 in second at around 70. It had lots of power climbing the 6% grapevine in second gear!Fred.

All you can get is a 3.55 or a 3.31 in a SRW diesel from Ford.DRW trucks can be equipped with the other ratios like 3.73.

Axle ratios | Good Sam Community

Lynnmor
Explorer
Mar 22, 2015
BenK wrote:

Less torque if going from 3.73 to 3.55

More torque if going from 3.55 to 3.73

If performance is higher on your have to have list...get the 3.73's

BUUUUUTTTT................. He CANT get the 3.73 in that truck.

The 3.55 will do just fine.
NC_Hauler
Explorer
Mar 21, 2015
BenK wrote:
About 9% diiference in torque

Less torque if going from 3.73 to 3.55

More torque if going from 3.55 to 3.73

If MPG is higher in your have to have list...get the 3.55's

If performance is higher on your have to have list...get the 3.73's

I'll always chose performance over MPG...opinions vary...

I for one, agree with you on this Ben....course I'm one of those "dummies" that has a 4:10. I do almost all my towing in the mountains though.
BenK
Explorer
Mar 21, 2015
About 9% diiference in torque

Less torque if going from 3.73 to 3.55

More torque if going from 3.55 to 3.73

If MPG is higher in your have to have list...get the 3.55's

If performance is higher on your have to have list...get the 3.73's

I'll always chose performance over MPG...opinions vary...
Javi1
Explorer
Mar 21, 2015
If I had that trailer I'd be looking at DRW... 3:73 is kick butt for pulling with the 6 speed.... 3:55 is better than the 3:31 in fact with that trailer the 3:31 will keep you in 4th or 5th at any overpass
ib516
Explorer II
Mar 21, 2015
All you can get is a 3.55 or a 3.31 in a SRW diesel from Ford.
DRW trucks can be equipped with the other ratios like 3.73.
Golden_HVAC
Explorer
Mar 21, 2015
Hi,

The rear axle ratio is picked out to give the best of both mileage, and performance. You will go up the hills a little faster when the engine RPM is higher, but get the best mileage at the lowest possible engine RPM.

So with modern 6 speed transmissions, you use the 3.55:1 rear axle and shift out of overdrive while going up a steep hill at 55 MPH!

I never really understood why anyone would want a 4.10:1 rear axle in a low RPM diesel truck. 3.55 is better. I had 3.73 with my 75 Ford and 3 speed, 460" engine. I would do around 2,500 RPM at 65 in drive, and 4,000 in second at around 70. It had lots of power climbing the 6% grapevine in second gear!

Fred.
rhagfo
Explorer III
Mar 21, 2015
agesilaus wrote:
The general thought today seems to be that with the 6 or 8 speed transmissions the axle ratio is not as important as it was during the 3 or 4 speed tranny days.

I have 3.55 in my 01, with 5 speed manual. I do fine in hills with it but at 16,000# I think I would want the 3.73.
If you have any thought of going big get the Dually now!
APT
Explorer
Mar 21, 2015
You'll never notice it with 800+ft-lb of torque.
agesilaus
Explorer III
Mar 21, 2015
The general thought today seems to be that with the 6 or 8 speed transmissions the axle ratio is not as important as it was during the 3 or 4 speed tranny days.

Forum Discussion

Axle ratios

About Travel Trailer Group

Related Content

Comparing axle ratios

rear axle gear ratio

Question about axle Ratios

Rear axle ratios

10 speed F150 axle ratios