What would be the main difference from going from a 3:55 rear end to a 3:73 rear.
Gas Miledge? More Torque? What would it do for me?

 

More torque, depends on the engine you have. I know my 3.73 have me running about 2100 rpm at 70, some guys run 80 at that rpm. I think it would impact mpg some but how much I don't know.

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- 2001 F150 Harley Davidson Special
- 1993 Mazda Miata, wifes car
- 1994 Harley Davidson Heritage
- 1976 Honda CB750K, Original
- 1965 Honda 305 Dream, Original
- 1971 Triumph Trophy 650, Original
- 1971 Norton Commando
- 1970 Honda Trail 90, Original
- Yamaha 500 Short Tracker, racing #69
- 1984 Yamaha Virago 1000, wifes bike
- 1981 Honda Passport 70, wifes bike
- My on-line album
- My Webpage

 

I've had both the 3.55s and the 3.73 LS and as stated above it isn't worth the money to change. As for towing, I have found out with the 5.4 and 3.73s your shifting (drive to overdrive) doesn't work as hard. Now put in a chip and have it programed for a nice firm shift and you"ll pull all day grinning.

By the way, I'm averaging 16.4 to 18.6 highway, and that's Rocking & Rolling..
I've had (3) 5.4s now and I won't even talk about in town MPG...

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DOGCAM
dogcam@f150guy.com
01 F-150 SC Lariat
Flareside 4X2,5.4,3:73
LS, SnugLid,Dynomax
Exhaust,Kenwood Amps,
Speakers,JL 10" Sub

 

I currently have 3.73 and want more torque...I am going to 4.10. If you are going to spend the money for the swap out...make it worth it and go 4.10.



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1998 F150 Nascar Edition(removed the decals)
4.6L V8 4x2 Reg Cab Short Bed
K&N Generation II FIPK
Borla Split Rear CatBack Exhaust
Stull Billett Grill
KC Hilites 150watt daylighters behind the grill
PIAA 1700 foglights in bumper
APC Clear corner lenses
Pirelli Scorpion ST (265/70/16)on factory Nascar Black Mag Wheels
Bug deflector
Side window deflectors
Snapless Tonneau Cover
Duraliner Bedliner
Alpine Head unit
Alpine Amp
Boston Acoustics Speakers
Bazooka Tube behind passenger seat

Future Mods:
Superchip
Torque Converter
JBA or Gibson Headers
Edelbrock Throttle Body
Traction Bars
IAS or Reflex Shocks
Anti-sway bars
Granatelli Mass Air Flow Sensor
Vortech Supercharger
Underdrive Pulley Set
Go Rhino Nerf bars
Crystal Eyes Projector headlamps
APC Euro Taillights

 

jjboods, I don't know if you can do this with the F-150 rears, but Id go with 4:40s on that Nascar truck. talk about torque......
But then again I don't know that much about the 4.6 truck engine???
You think about it your only going up .37 gear ratio.
Dogcam

 

To be honest, the one thing about this truck that pisses me off is the totally @$#$ing useless 3.55 gears. It's a disgrace that Ford didn't offer the 3.73 for the '00 models. I wouldn't mind having to turn off OD if I were towing a 5000lb trailer up the H2. But running empty I start at the bottom at 65mph and within a mile my speed just keeps dropping. My foot is to the floor but nothing ... and this is empty. I turn off the OD and now I'm at 3000rpm and can keep my speed up. I guess a 4.10 is the only solution. I'd probably use less gas because I could stay in OD at 2500rpm.

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'00 5.4L AUTO 4X4 F-150 Lariat
'98 4.0L 5spd Jeep Wrangler Sport
'02 F-350 PSD CC DRW 6SPD 4X4 Lariat (order this year)
www.hawthorn-engineering.com

 

Gah, I had a 97 F150 4x2 with tow package, w/ 5.4 and 3:55 gears. I towed a 12' Uhaul from Phoenix to Vermont loaded. And was able to cruise at 80MPH with no problem up or down hill. It sounds like there is something wrong with your truck.

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2000 F-150 XLT 4x2 F/S Reg Cab 5.4 3:55LS< >Borla Catback Dual Out Back<>Kenne-Bell Supercharger 6LB Boost<> SuperChip> Best ET 14.98,Best R/T .572 Soon to be installed: Baumann Shift Kit Fri 29 Jun

 

I agree with acadianbob.

My 97 had 3.55; and Nick has 3.73's. The difference is barely perceptible.

Actually, I think the current truck is doggy off the line, since it has a 1900 RPM stall converter -- and the 97 had a 2600 RPM (I think) stall converter.

The new truck tows quite well, however -- and I'm towing the same trailer that I've had with a 6.2Diesel 3.42 and the 5.4 3.55 and now the 5.4 3.73.

The only thing better would be the V10.

The gear ratios with the 3.73 are PERFECT in all gears -- nice work, Ford.


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Y2K™ Jim - N8JG@Hotmail.com

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

 

I had an '99 Expy with the 5.4L and 3:73, it was pretty peppy off the line and got about 12mpg city/16 mpg highway. Now I have a 5.4L and 3:55 rear and only get 10 mpg city but 17 mpg highway, kinda dissapointing on takeoffs but still acceptable to avoid traffic. If you drive mostly city you may actually get better mileage with a lower ratio. If I was changing gears I'd definitely go 4:10, the 3:73 is only a 5 percent difference.

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'01 EB Expy 4x4, 5.4L, 3.55LS w/tow pkg, 4 Wheel Air Suspension, Moonroof

 

evo
What could be wrong? It seems to run fine in all other gears i.e. 1,2 and D but OD is only good on flat roads. Mine is a 4x4 with the ORP so I have the bigger tires and the extra drag of the front half-shafts. I should check ... Ford probably gave me a 3.08 rear gear!!! My performance mods include a Gibson exhaust (sweptside), K&N filter, WMS velocity tube and Baumann shift kit. I average 13mpg mixed city/freeway driving. Any ideas or checks I can perform to determine if something's wrong?

Y2K
Surely your '00 truck didn't come with 3.73 gears? But I'd agree with you, a 3.73 would probably make enough difference over a 3.55 that a 4.10 swap would be a luxury rather than a necessity.


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'00 5.4L AUTO 4X4 F-150 Lariat
'98 4.0L 5spd Jeep Wrangler Sport
'02 F-350 PSD CC DRW 6SPD 4X4 Lariat (order this year)
www.hawthorn-engineering.com

 

If you have 3.55 gears now, a change to 3.73 would be nearly imperceptable and way too much time and money. If you currently have 3.08s, either gear set would be helpful. MOre acceleration, more rpms, less fuel mileage. 3.55s might be easier to get your speedo correct.

 

Depends.... What are your intentions? Bigger tires? Do you haul stuff or tow? Weekend wheeln'?

If all you do is swap gears and keep the same tires, you will have more torque like Irutt said. Your engine will also turn more RPM's at highway speed which = less mpg. But you will be able to haul and tow easier.

Just to compare, I have the 3.55's and I did put on slightly larger tires and I only turn 1900 rpm's at 70. I've changed the speedo gear to compensate, so I know this is really close.

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1997 F150 4x4 XLT, SuperCab, Short Box, 5.4, Royal Blue/Silver, K&N, Gibson SS, LT265/75/16 Wild Country APT's, Hellwig Progressive Springs (LP-25)

 

Those reatio's are very close. The only difference would be felt when towing a HEAVY load. 0-60 times might change .1-.2 seconds. Gas mileage will probably go down a bit.

 

Yes, I have the same problem sometimes. My truck will down shift from OD to D going up a small hill. When I am driving I am constantly turning the overdrive off, this is why I posted this topic originally. I was wondering if I would actually get better gas miledge and performance changing to 3:73 because as it is now, the only time I can affectivly use the OD is when I am on the flat hwy. I currently am running 3:55, I think 4:10s would be to much. what about something between 3:73 and 4:10, would that be worth my while. I don't know a lot about truck rearends so I don't know if they offer a different ranges between. I also hope to put 20" wheels on it in the future. This could be a factor as well.
Thanks

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98' STX, Silver,
Mods: 3" PVC intake
Future Mods: Electric Fan (better gas miledge)
3" PVC Ram Air
3-4" Lower (need kit cheap)
Maybe one day supercharger
84' Mustang SVO 158k(rebuilding)
87' Suzuki LT500 Quadzilla

 

Go from 3.55 to 4.10 and then if you go to a larger tire like some of us you will end up with an effective gear ratio of 3.73 to 3.90 which should be okay.