Gears
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Freshman User
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Gears
Not to beat a dead horse!!!! I have read posts on here about gears, and have even asked questions myself, and I am still wondering. My truck, 03 F250 V-10 auto w/ 3.73 4x4 and 33's on all 4 corners. My rpm's @ 70 are right @ 2000, when towing my Fifth Wheel #8000 in 3rd my rpm's are around 2750. Will 4.30's be a better bet for me? If so how will they help? Will they allow me to pull in O/D or will 3rd be the way to go yet? I suppose I am still used to having the power of the diesel (torque). Any help will be appreciated.
Post Fiend
Joined: Jun 2003
Posts: 5,643
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From: NE Texas
Welcome to FTE 
I have 4.30 gearing and always pull in 5th gear (OD), but I have a manual tranny. If towing often, in my opinion, the 4.30's would be the way to go.
Maybe someone with an auto tranny with experience in this will chime in.
I have 4.30 gearing and always pull in 5th gear (OD), but I have a manual tranny. If towing often, in my opinion, the 4.30's would be the way to go.
Maybe someone with an auto tranny with experience in this will chime in.
Logistics Pro
Joined: Jan 2002
Posts: 3,733
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The key is in you last part about diesel torque... if you want that feel and you want to raise your cruise rpm back into a better Sweet spot when hauling the 4.10 or 4.30 gear set is about right for your set up...being a 4x4 you need both front and real done
In my opinion this is the best bang for the buck upgrade a V10 can be given.... if your current set up has the speed calibrated for the 3.73 and 33 tires you will NOT need a new calibration but I recommend you re-boot the PCM( disconnect the battery) and re teach it the new RPMs and shift points if you change to lower gewars....
In my opinion this is the best bang for the buck upgrade a V10 can be given.... if your current set up has the speed calibrated for the 3.73 and 33 tires you will NOT need a new calibration but I recommend you re-boot the PCM( disconnect the battery) and re teach it the new RPMs and shift points if you change to lower gewars....
Senior User
Joined: Oct 2005
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From: SPARKS NEVADA
I agree Fred the best thing I did was switch from the 3.73 pulling a 7,000 TT to the 4.30's when I got the 10K 5th. The rpm's at 65 are right around 2,125 in OD, with stock tires. You'll have to do th emath to calculate what your would be, if I had to do it over I'd go up 1 more to the 4.56's, just because of the increased towing capacity of going form 3.73's to 4.30's.
Cargo Master
Joined: Apr 2003
Posts: 2,058
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From: Too close to Houston
How about an underdive unit? Gear Vendors (there's another, but the name escapes me now) makes a 80% underdrive auxiliary transmission that bolts behind your transfer case. That would give you the effect of a 4.66 axle ratio when you need it and you keep the benefits of the 3.73 when you don't. It would only work in 2WD, but that covers 99.99% of your towing situations.
Posting Guru
Joined: Nov 2004
Posts: 1,708
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From: North Dakota
Yeh, I'm curious what a GV unit costs, anyone know. If the price is comparable to doing a front and rear gear change it would acutally probably be the way to go.
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Senior User
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From: SPARKS NEVADA
I checked out the cost of the GV and if I recall the cost was around $3,800 as compared to the $1,600 for switching gears. I was going to install the GV, but decided aginst that because I wasn't comfortable installing something likethat. There are some threads on the GV from a while ago.
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When I pull my rig, I run in 3rd gear, which puts me at about 2750 RPMs @ 70 MPH. I looked at the Gear Vendor site, and they have a final drive chart with several different gears for the transmission that I have. The part that confuses me is this, most seem to pull in O.D. Now say with 4.30 gears the final drive accourding to Gear Vendor site wil be about 3.35 which is less than my current 3rd gear final which would yield a lower RPM. Even the switch to the 4.56 gears would yield a lower RPM than what I currently have running in 3RD. So what is the advantage of having the lower gears. I think I want a higher RPM, or am I out of the sweet spot for the V-10 at 2750?
Last edited by fifth wheel; Jun 6, 2007 at 09:33 PM.
Cargo Master
Joined: Apr 2003
Posts: 2,058
Likes: 424
From: Too close to Houston
I think the charts they post are for overdrive units (double overdrive or gear splitting). I think what you would want would be an underdrive which gives the same 20% change, but in the other direction. Can still be used for gear splitting. I don't do a lot of trailer pulling, so when I looked at this I thought for me the best fit would be factory 4.30's and a GV overdrive. If I was pulling a lot I'd go with 3.73's (3.55's if I could get 'em) and a GV underdrive.
Senior User
Joined: Oct 2005
Posts: 259
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From: SPARKS NEVADA
It took me a while to get the feel of my 4 speed 4R100 transmission. When towing at first the trannie would shift from 3 to 4th and I had a hard time keeping it in the gear I wanted. Reviewing the torque and rpm charts for the V10 I now know that the sweet spot is around 3,200 rpms for max torque in 3rd gear going up steep grades. I have no problem towing now with gear upgrade and keeping the rpms in the right area.
Junior User
Joined: Feb 2006
Posts: 77
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From: SLC, UT
I have a 99 250 V10/auto with 33"s, 4.56s and pull 14k on my 5th for a total weight of 21K. I tried it with 3.73s and no OD on the flats, it was good. However, takeoff and the mountains (Utah) were awefull. I chose 4.56 to keep me right around 2500 @ 70 in OD and it does great on the flats but, needs to slow to 3K at 60mph in the smaller hills to keep from kicking in and out of OD. The 8K+ FT summits require me to run 4K in second to stay at 45-50mph with 175 degree trans temps. To do it again, I would probably have gone with 4.88s to keep the RPMs up in OD or chose 4.30s and run 65MPH without OD.
Either way, a gearswap is THE best bang for the buck.
HTH -Marcus
BTW. I only lost 1 MPG on the highway unloaded and heavy towing averages the same 7.5-8.5 MPG.
Either way, a gearswap is THE best bang for the buck.
HTH -Marcus
BTW. I only lost 1 MPG on the highway unloaded and heavy towing averages the same 7.5-8.5 MPG.
Last edited by ATXZJ; Jun 7, 2007 at 11:03 PM.