Pros/Cons for Under/Overdrives?
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Pros/Cons for Under/Overdrives?
Searching for solutions to my towing dilemma.
E350, 460 EFI, E4OD, 4:10 gears, 10,000lb. TT. Turning 2300 rpm @ 68-70 mph, tranny wants to hunt back and forth b/t 3rd & od. 460 lacks torque to pull modest hills. Son starts college next fall, so new truck payments are not an option for now. Concidering the bolt on under/overdrive approach. Any first hand experiences would be helpful.
E350, 460 EFI, E4OD, 4:10 gears, 10,000lb. TT. Turning 2300 rpm @ 68-70 mph, tranny wants to hunt back and forth b/t 3rd & od. 460 lacks torque to pull modest hills. Son starts college next fall, so new truck payments are not an option for now. Concidering the bolt on under/overdrive approach. Any first hand experiences would be helpful.
Cargo Master
Joined: Jul 2000
Posts: 2,281
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From: Northern California
I don't think it would help at all. If your tranny has an OD lockout switch then the over/under would have you lockout OD and run in third, then use the over/under. BUT the over under from GV is 1:1 1:1.27 (i think), so you'd get overdrive or direct. No change from what you have now.
I think your best bet is to keep it in 3rd IF you have the OD lockout, I think most do.
The over/under is really just a direct / over. The under part comes from the fact that you have 1, 1 over, 2, 2 over, 3, 3 over...
So 2 over is also know as 3 under.
If keeping it in 3rd doesn't do the trick, might want to look at a gear change. check the web for a chart to see what happens with 4:55 gears
The 460 should have the power to pull most hills, even loaded. I'd check to see if something is wrong with the engine.
I think your best bet is to keep it in 3rd IF you have the OD lockout, I think most do.
The over/under is really just a direct / over. The under part comes from the fact that you have 1, 1 over, 2, 2 over, 3, 3 over...
So 2 over is also know as 3 under.
If keeping it in 3rd doesn't do the trick, might want to look at a gear change. check the web for a chart to see what happens with 4:55 gears
The 460 should have the power to pull most hills, even loaded. I'd check to see if something is wrong with the engine.
FTE Leadership Emeritus
Joined: Sep 2000
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From: Southern California
Welcome to FTE MARKC4! Thanks for joining us in the Towing forum! 
I would agree with karljay. A ring and pinion gear change would probably be more beneficial and less expensive for your intended use. Even with a good axle ratio like 4.10, oversize tires will also reduce effectiveness.
Check out the tire size and gear ratio calculators HERE
I would agree with karljay. A ring and pinion gear change would probably be more beneficial and less expensive for your intended use. Even with a good axle ratio like 4.10, oversize tires will also reduce effectiveness.
Check out the tire size and gear ratio calculators HERE
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Thanks guys,
I'm running stock 245/75R16 tires and may concider 225's as a cheap way out.
By GV's spec. thier overdriving .78:1. Running straight 3rd gear I'm turning an extra 1,000rpm (3,200) and the 460 is sucking hard on the fuel gauge. GV dash control allows you to lock out double overdrive (4 over) for towing while still spliting the other 3.
So 3 over would give me 2460rpm/3.20 final drive instead of 2240rpm/2.91, just enough to keep me out of straight 3rd pulling the hills?
The only way I'm concidering the GV is because I've found a used one for cheaper than new and wanted some feed back.
I'm running stock 245/75R16 tires and may concider 225's as a cheap way out.
By GV's spec. thier overdriving .78:1. Running straight 3rd gear I'm turning an extra 1,000rpm (3,200) and the 460 is sucking hard on the fuel gauge. GV dash control allows you to lock out double overdrive (4 over) for towing while still spliting the other 3.
So 3 over would give me 2460rpm/3.20 final drive instead of 2240rpm/2.91, just enough to keep me out of straight 3rd pulling the hills?
The only way I'm concidering the GV is because I've found a used one for cheaper than new and wanted some feed back.
Cargo Master
Joined: Jul 2000
Posts: 2,281
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From: Northern California
Make sure it's for you setup, they have different adapters for each application. The standard price for a used unit is about 500~800 and the cost for a factory rebuild is $750.
If you can find one for 800 or less, and it fits your truck, then I'd grab it. Even if it dosen't help with that one problem, you'd still get the double overdrive for use on flat drives.
If you can find one for 800 or less, and it fits your truck, then I'd grab it. Even if it dosen't help with that one problem, you'd still get the double overdrive for use on flat drives.
Mountain Pass
Joined: Jan 2002
Posts: 200
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From: Middleburg, Fl
I put a US Gear underdrive on my 85 F-350 460 c-6. It gives me 18% reduction for pulling. I still have trouble with my 5'r on step inclines. About 10-11k on the trailer (Jayco Designer 32) 4:10 rear. Getting into Alabamas' highest park was a tough run flat out in reduction gear at about 17 mph.
MT
Found my US Gear on e-Bay used at $345.00 shipped, a great deal.
MT
Found my US Gear on e-Bay used at $345.00 shipped, a great deal.
Post Fiend
Joined: Apr 2004
Posts: 6,473
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From: Lafayette, IN
I'm just curious why you'd be towing 10k lbs. with that setup at 70 MPH. That load is borderline for the 460/E4OD to begin with, but 70 MPH really compounds the problem. Drop down to 55-60, and I bet your tranny doesn't hunt.
Jason
Jason
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Originally Posted by jroehl
I'm just curious why you'd be towing 10k lbs. with that setup at 70 MPH. That load is borderline for the 460/E4OD to begin with, but 70 MPH really compounds the problem. Drop down to 55-60, and I bet your tranny doesn't hunt.
The hunt more remark is from experience. when I drive 55-60mph when towing my TT & boat with the V10 it has no idea which gear to be in (3rd or 4th) but when I run 70-75 it doesn't have a problem. the reason is is because at 55-60mph I'm not yet in my power band and at 70 I'm just getting into it. BTW I have 3.73s and 33" tires so that isn'texactly helping me either but it the same Idea. heck at 70mph in 4th I'm running less than 2k rpms. just run it in 3rd and fill it up when shes emty, everything will be much happier other than you're wallet. if nothing else just change the gears!
Last edited by SLE; Sep 12, 2005 at 11:08 AM.
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I'm concidering the Under/Over to get my rev's in the middle of 3rd & OD and still be able to drive the thing when I'm not towing.
Here's how the math works out.
245/75R16 Tires, 30.5"
4:10 Diff.
@70 MPH
3rd Gear; 1:1, 3160 rpm,
More noise, More Gas, No Shifting
3rd and Gear Vendor's Over Gear; .78:1, 2470 rpm.
Less Nosie, Less Gas, Less Shifting
Ford OD Gear; .71:1, 2245 rpm,
Quiet, Less Gas? Maybe not?, A lot of Shifting.
Ford OD and Gear Vendor's Over Gear; .55:1, 1740 rpm,
Quiet, Less Gas, No Towing
A 4.55 gear change would put me in the same ball park as the 4.10 w/ Gear Vendors under/over but would require a housing change as well.
Here's how the math works out.
245/75R16 Tires, 30.5"
4:10 Diff.
@70 MPH
3rd Gear; 1:1, 3160 rpm,
More noise, More Gas, No Shifting
3rd and Gear Vendor's Over Gear; .78:1, 2470 rpm.
Less Nosie, Less Gas, Less Shifting
Ford OD Gear; .71:1, 2245 rpm,
Quiet, Less Gas? Maybe not?, A lot of Shifting.
Ford OD and Gear Vendor's Over Gear; .55:1, 1740 rpm,
Quiet, Less Gas, No Towing
A 4.55 gear change would put me in the same ball park as the 4.10 w/ Gear Vendors under/over but would require a housing change as well.
Post Fiend
Joined: Apr 2004
Posts: 6,473
Likes: 4
From: Lafayette, IN
I guess I didn't really make myself clear there. There's nothing really wrong with the 460 end of the deal, but the E4OD is a bit of a weak point. I sure wouldn't want to be yanking around a 10k trailer with an E4OD in OD at 70. Nobody should be pulling a trailer that fast anyway. Nowhere. No how. I forgot to say that he should drop to 55-60, and lockout OD--tow in 3rd. That would put the 460 more in its powerband, reduce heat in the tranny, and just plain make it safer for everyone else on the road. Sure, towing in 3rd is more gas, but it's not that much extra to where you'd pay for a O/U-drive anytime this decade, unless you were towing day in, day out.
Jason
Jason