change gearing ?? - Diesel Forum

hdrider · 06-18-2006, 08:27 PM

I have a 2005 F350 4x4 CC DRW LB King Ranch that I like very much. It has 4:10 gears.
I have on order a 5th wheel that has a GVWR of 16000lbs. My truck is rated at 15600 I believe. I know I do not have to load the trailor to the max but..
I was thinking of changing the gears to maybe a 4:30 instead of getting another truck. Would that take care of my problems or what would be the draw backs ??
The new 5th wheel book says Axle weight 7520lb,, Hitch weight 2425lb GVWR 16000lb,, my sandaril is 1900lb then add 20 gal fuel for gen, gas in fuel station of up to 40gal, plus the basics.
I'm not sure what it would cost to change the gears but it has to be cheaper tha buying another truck.

barrelhorses · 06-18-2006, 08:33 PM

Wait until you tow the new 5er before considering the gear swap. I don't think changing from your stock 4.10 to 4.30 will make that much difference. I bet your current set up will get the job done just fine. I have the 3.73 gears on my SWR and my horse trailer has a GVWR of 18K. I don't know what it really weighs loaded, and frankly I'm not sure if I want to know, but the truck does just fine with it.

DRJ48 · 06-18-2006, 08:42 PM

I agree with Barrelhorses, a 4.10 to 4.30 swap will not change much and your truck should handle it fine as is. [img]/ubbthreads/images/graemlins/smile.gif[/img]

SmokeyWren · 06-19-2006, 10:40 AM

[ QUOTE ]
... 2005 F350 4x4 CC DRW ... 4:10 gears.
I have on order a 5th wheel that has a GVWR of 16000lbs. My truck is rated at 15600 I believe.

[/ QUOTE ]

GCWR 23,500 minus 16k trailer leaves 7,500 pounds for the wet and loaded tow vehicle without exceeding GCWR of the tow vehicle. Yeah, your tow vehicle is going to weigh a lot more than 7,500 pounds.

With the 4.30 rear end, you'd have a GCWR of 26,000, or 2,500 pounds more towing capacity. So then your truck could gross 10k without exceeding the GCWR of the truck. And it probably won't gross more than about 9,000 without the trailer.

So theoretically, the 4.30 rear end is the answer for you.

But as others have suggested, I wouldn't spend a dime until after you make a few long trips towing the wet and loaded trailer. If you don't often climb mountains or mountain passes with the wet and loaded rig, you'll probably like your 4.10 rear end just fine.

[ QUOTE ]
I know I do not have to load the trailor to the max but..

[/ QUOTE ]

But you will. [img]/ubbthreads/images/graemlins/shocked.gif[/img]

[ QUOTE ]
Would that take care of my problems or what would be the draw backs ??

[/ QUOTE ]

The only drawback would be reduced fuel mileage when running around unloaded. And a bit more road noise caused by the 5 percent more engine RPM at the same speed. If you use the truck as a commuter car, then you don't want the shorter legs unless absolutely necessary to drag the trailer over the Rockies on I-70 or I-90 - or similar high mountain passes. Or "The Grapevine" in SoCal.

[ QUOTE ]
I'm not sure what it would cost to change the gears but it has to be cheaper tha buying another truck.

[/ QUOTE ]

Not cheap on a 4x4, because you have to change both diffs.

RBP04 · 06-21-2006, 01:33 AM

We tow are 40 ft cl40 weekend warrior 5th wheel, 24000 +/- gcwr with are 05 dually to pismo ,the river,and glamis , we have 4.10 and It tows it fine. but I would also like to know how much better it would do with 4.30,We also have a f-550 with 4.88 and the rpm on the freeway at 70 is 2800, witch is not a good commuter

hdrider · 06-21-2006, 08:44 AM

I think I will wait until I get the 5th wheel and play it by ear the way it sounds. I will at least put the air assist on the suspention before it gets here I think.
I thought about the F550 and the 4.88 gears, but the truck is my daily driver and was a bit concerned.
Ford told me $2800 to change out the gears if I decide to.

RBP04 · 06-21-2006, 11:44 AM

yes I would reccomend puting the air bags on the rear, the new trailer will dump the back off the truck and will leave about 2 inches from the bump stop, every bump you hit will make it hit the bump stop. I installed the part#2400 firestone ride rites that mount inside the frame rail because of where the hitch is mounted on the frame rail. install was easy,and it fixed all the problems and rides really good.

desertsands · 06-21-2006, 02:45 PM

I pull a 38' toybox to all the same places as mb350 (not so much to Glamis anymore) with the truck in the sig. I changed out the 3.73's to 4.56's and with my tire size i'm running at about 4.10's and the thing pulls just fine. If you go with the Firestone's I have the kit that mounts to the frame rails like mb350 but with my exhaust it comes a little close the air bag so I fabed up a stainless steel sheet the protects the heat from getting to close. But I like making things out of stainless [img]/ubbthreads/images/graemlins/cool.gif[/img]

CascarFan · 06-26-2006, 06:15 PM

[ QUOTE ]
I was thinking of changing the gears to maybe a 4:30 instead of getting another truck.

[/ QUOTE ]

I'd drive the truck for a while and if you do decide to go for a change, I'd look into an auxillary tranny before swapping out rear end gears. That way you have the best of both worlds and according to your quote, not that much more either. There's 2 on the market that I'm aware of, US Gear and Gear Vendor.

vince90605 · 07-01-2006, 11:51 AM

I have 35" tires and A gearvendor unit, I tow A 33 foot 5th wheel toybox weighing 13500 lbs. I just changed my gears from 3.73 to 4.56 , so far driving around town my mpg has gone up and on the freeway in double overdrive at 70 mph I turn 1650rpm and ave. 18-19 mpg. I have not towed with the new gears yet , I am still breaking them in but I am planning A trip to oregon in about 3 weeks so it will make A good test. I don't really notice much of A change driving around town as far as extra torque but my shift points seem to be back to where thay need to be since I have oversized tires and the most impressive thing is my egt's have dropped about 300 degrees. I think I was geared so low before I was lugging the motor down and my egt's were limiting me big time before. Everyone tells me once I tow with it I will notice A huge differance, I am kepping it easy right now untill I put some miles on the new gears but so far I love the change. The shop that did the change asked if I wanted to go with 4.88's or 4.56's I wanted the 4.56's to still get decent mpg's when I'm not towing. The gears cost me A little under $1400 for both front and rear since I have A 4x4.