Changing Gear Ratio - Will It Help?

[Jeebs79]

Hi everyone!! My wife and I picked up a brand new 2012 Cougar 29RBK a couple days ago. Very nice, very big lol. We have been camping with a popup for 10 years now so this will be a bit different.

My only worry is that it might be putting more stress on my truck than I had thought. I have a 2010 F-150 with the 5.4 Triton V8 and a 3.55 differential. Seems to me that switching to a 3.73 would help a lot with off the line performance and gas mileage. Any thoughts? Thanks!!

[Englishman]

Welcome to the forum good luck with the new camper. As a general rule you don't want to pull more than 80% of
The max the max tow rating of the the truck. You need to work that ot from the max weight of the trailer not dry weight.To give you more information then you will need to provide the group with more information on, your truck. If it was me I would be looking at minium of f250 or 2500 truck.

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[Festus2]

Jeebs79 -
If you are looking for "quick get-aways" from stop signs or other "off-the-line" situations and you are pulling an RV, changing your gear ratio slightly might result in some increase in acceleration. However, anyone pulling an RV should not be expecting too much in the way of "off-the-line" performance. You put your foot down on the pedal and pull away - SLOWLY.
Have you figured out your mileage that you are presently getting with your RV in tow? Perhaps those here who are more knowledgeable might comment about any increase in mileage you might expect by a gear ratio change. My guess would be that the cost of making this modification might wipe out any benefit you might see in decreased fuel consumption.

[Englishman]

To swap out the gear ratio on my chevy 2500 from 3.73 to 4.10 would cost around $1500 per axle. The high the ratio the less miles to the gallon. With that said I get more mpg towing with the 2500 then I did with f150 low 8 on the ford low 10 on the 2500. A bed cover increases the mpg by over 10%.
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[therink]

Congrats on the new trailer. You are definitely going to give the transmission a work out with 3:55. What is the loaded GVWR of the trailer. What is the tongue weight? Figure 15% of trailer GVWR. What is the GVWR of the truck? Subtract weight of the passengers, gear, firewood, bikes, hitch and what is leftover is for trailer tongue weight. You may be pushing the limit for the truck. Hopefully not.
Steve

[Jeebs79]

OK, so my truck's max tow capacity is 9600. The GVWR for the truck is 7200. 80% of max tow is 7600.

The trailer is listed at 6566 lb with 1634 lb load capacity. The GVWR is 8200 with a tongue weight of 835.

I am not going to the drag races with a 7000 lb tailor. With my 3.55 rear end it seems that the truck struggles to get moving (more than I thought it would). All I am asking is whether or not a 3.73 differential would help.

[christopherglenn]

Will a 3.73 help, yes. Would a 4.10 help more, yes. Is it worth the ~$1500?? don't know.

[f6bits]

It sounds like you’re well within towing limits. How about payload? The tongue weight can easily approach 1,000 and is probably over 900 already.

Before making the jump to the 3.73, I’d give it more time. Accelerating should be done slowly – no hurry there. I’d be more concerned about how it does on hills. If it doesn’t struggle on hills, leave it alone. Your 3.55 will get you better gas mileage when not towing.

[JRTJH]

Jeebs79

I tow a fifth wheel (normal "trip ready" towing weight of 7200 lbs) with my 2010 F150 FX4 (electronic 3.73 axles) and 6 speed automatic transmission. On accelleration, I know the trailer is back there. Previously I towed other trailers near the same weight with a 1972 Dodge W200 (360 cu in) and with a 1993 Ford (7.3L diesel NA) and a 1999 Ford (7.3L turbo). When towing, with ALL of those tow vehicles, I KNEW the trailer was back there and experienced "sluggish" accelleration.

Assuming you've weighed your trailer AND truck and are not exceeding the GCWR, GVW and max trailer weights for your truck (it looks like you may be close) you will definitely feel "sluggish" accelleration with the trailer in tow. I'd say that with all my previous towing experiences, I've never had a vehicle that performed the same with and without a trailer in tow.

My suggestion would be to pay closer attention to how the rig performs at normal cruising speeds. If the transmission is constantly shifting between 5th and 6th gear (or lower) and won't maintain speed when travelling on "level ground" without shifting, then you may benefit from a rear end change. But, if your rig does maintain cruising speed without frequent shifting, then I'd think you're pretty much OK (if within the weight limits)

Keep in mind that the cost to change out both axle gears in a modern vehicle may well cost more than trading it for a better equipped vehicle.

I know of nobody who can boast that their tow vehicle will accellerate to 60MPH in the same time with and without their RV connected. Slow accelleration (within reason) is just a part of RVing.

John

[Jeebs79]

Thank you for all your thoughtful responses. I called Ford this morning and they verified that I am within spec for the trailer. They also said that I would mess up my warranty if I replaced the diff. That said, I will be patient and see how it goes. We are all dieing to do our first trip.

Thanks again.

[rhagfo]

Jeebs79

I tow a fifth wheel (normal "trip ready" towing weight of 7200 lbs) with my 2010 F150 FX4 (electronic 3.73 axles) and 6 speed automatic transmission. On accelleration, I know the trailer is back there. Previously I towed other trailers near the same weight with a 1972 Dodge W200 (360 cu in) and with a 1993 Ford (7.3L diesel NA) and a 1999 Ford (7.3L turbo). When towing, with ALL of those tow vehicles, I KNEW the trailer was back there and experienced "sluggish" accelleration.

Assuming you've weighed your trailer AND truck and are not exceeding the GCWR, GVW and max trailer weights for your truck (it looks like you may be close) you will definitely feel "sluggish" accelleration with the trailer in tow. I'd say that with all my previous towing experiences, I've never had a vehicle that performed the same with and without a trailer in tow.

My suggestion would be to pay closer attention to how the rig performs at normal cruising speeds. If the transmission is constantly shifting between 5th and 6th gear (or lower) and won't maintain speed when travelling on "level ground" without shifting, then you may benefit from a rear end change. But, if your rig does maintain cruising speed without frequent shifting, then I'd think you're pretty much OK (if within the weight limits)

Keep in mind that the cost to change out both axle gears in a modern vehicle may well cost more than trading it for a better equipped vehicle.

I know of nobody who can boast that their tow vehicle will accellerate to 60MPH in the same time with and without their RV connected. Slow accelleration (within reason) is just a part of RVing.

John

Great advice from one experienced in towing, when you start towing more than your TV weight, you will know it is back there when starting out.

[Mighty Ming]

Let us know how the first trip goes towing but really more about how much you enjoy that new trailer! Good times.


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