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04-17-2015, 08:17 PM
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#1
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Junior Member
Join Date: Oct 2013
Posts: 10
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Rear axel gearing
I have a 2wd 98 e150 with a 6 inch lift, 5.4 triton v8 and an Aod transmission. I am going to install a trutrack and new gearing. I am not super familiar with the ford 5.4 liter triton motor. I plan on running at 285-70-16 tire. Currently have 3.55 gears, but I am not sure what the optimum RPM for that motor would be for 70mph. I may occasionally pull a light raft trailor but nothing heavier then that.
Any help would be appreciated.
Thanks
Mike
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04-17-2015, 11:13 PM
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#2
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Senior Member
Join Date: Jul 2011
Location: Flagstaff, AZ
Posts: 2,001
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Re: Rear axel gearing
__________________
2005 E350 RB 6.0 PSD for extended fun
1989 Landcruiser FJ62 for local fun
2011 VW TDI Golf for hwy fun
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04-18-2015, 05:10 AM
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#3
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Junior Member
Join Date: Oct 2013
Posts: 10
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Re: Rear axel gearing
joeH the calculator and info in the trutrack was helpful. I am more concerned with gear ratio selection. Currently with the 3.55 gears @ 70 MPH the engine runs about 1800 RPM. I don't think the converter is even locking up and I cant use overdrive unless I am driving on a perfectly flat road with nonexistent headwind. From the aforementioned calculator @70MPH 4.10=2046 RPM, 4.30=2145 RPM, 4.56=2275.
Which one would be the best choice?
Mike
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04-18-2015, 05:28 AM
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#4
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Senior Member
Join Date: Jun 2012
Location: Unterfranken
Posts: 456
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Re: Rear axel gearing
I would go with 4.56
4.1 is still too long and 4.3 is a bad choice as it is a not very durable combo.
__________________
www.Dieda-unterwegs.net
2001 SMB E350 4x4 7.3 Powerstroke
1968 Pontiac Firebird 400 Convertible ,1978 Peugeot 504 Convertible,1988 Porsche 911 Carrera 3.2,KTM 300 EXC,BMW G/S Paris Dakar,BMW "Diabolo"
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04-18-2015, 09:38 AM
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#5
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Senior Member
Join Date: Jul 2011
Location: Flagstaff, AZ
Posts: 2,001
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Re: Rear axel gearing
I don't know what the optimum RPM is on the triton but 4.56 seems a bit much unless you're really off-roading or pulling a 10,000lb load. I suspect your raft trailer is much lighter than that. 2000lb?
4.10 gears with 35" tires is about right for me. Enough gearing to tow but not too high of an rpm on the hwy.
__________________
2005 E350 RB 6.0 PSD for extended fun
1989 Landcruiser FJ62 for local fun
2011 VW TDI Golf for hwy fun
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04-18-2015, 09:55 AM
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#6
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Senior Member
Join Date: Jul 2011
Location: Flagstaff, AZ
Posts: 2,001
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Re: Rear axel gearing
I don't know if he sold it but you could by Oldbonesclimbers semi-float rear axle with 4.10 gearing for cheap. Might be bolt and play and you could upgrade to discs on the rear.
viewtopic.php?f=7&t=15383
Have a look at Carringb's post regarding putting gears bigger than 4.10 in a semi-float rear axle.
viewtopic.php?f=39&t=13531
__________________
2005 E350 RB 6.0 PSD for extended fun
1989 Landcruiser FJ62 for local fun
2011 VW TDI Golf for hwy fun
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04-18-2015, 10:38 AM
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#7
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Senior Member
Join Date: Feb 2014
Location: Santa Maria, CA
Posts: 586
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Re: Rear axel gearing
I think that for your intended use 4.10 would be ideal. I have a 2wd e350 EB with 5.4L and 285/75/17 (34.1" tall) tires and 4.56 gears and it has the pulling power I needed but is much lower than necessary for non-towing freeway driving. If the van is empty, it can hold overdrive up most grades with 4.56's. I'll probably go to 35"s next time I need tires to bring the RPM down a hair (ya, ya, that's why!)
With your proposed 285/70/16 tires (31.7" tall) 4.10's would have you at 2129rpm at 70mph or 1977 at 65mph. That's pretty much the same RPM you would see with 4.56 and 35"s...sounds about right to me.
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04-18-2015, 04:12 PM
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#8
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Junior Member
Join Date: Oct 2013
Posts: 10
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Re: Rear axel gearing
Thank you everyone, that's exactly the info I was looking for.
Mike
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04-19-2015, 01:48 AM
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#9
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Senior Member
Join Date: Jun 2012
Location: Unterfranken
Posts: 456
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Re: Rear axel gearing
Please keep us update what your experience is after the change
__________________
www.Dieda-unterwegs.net
2001 SMB E350 4x4 7.3 Powerstroke
1968 Pontiac Firebird 400 Convertible ,1978 Peugeot 504 Convertible,1988 Porsche 911 Carrera 3.2,KTM 300 EXC,BMW G/S Paris Dakar,BMW "Diabolo"
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04-19-2015, 06:51 AM
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#10
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Senior Member
Join Date: Sep 2011
Location: Rancho Nuevo (Cabo/Todos Santos) B.C.S. and San Diego, CA
Posts: 1,952
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Re: Rear axel gearing
4.10 is just barely enough gear for a 33" tire and 5.4L on a heavy rig, not enough for 35" tires. I would say that it also depends on what year your 5.4L is.
__________________
Four time Baja 1000 winner, four time Baja 500 winner. Solo'ed the Baja 1000 to LaPaz/Cabo twice.
4-Wheeling since 1972, Desert Racing since 1989.
AgileOffRoad.com
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