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  #1  
Old 06-27-2001, 11:20 AM
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Question 3:55 compared to 3:73

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?
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  #2  
Old 06-27-2001, 11:25 AM
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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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  #3  
Old 06-27-2001, 03:18 PM
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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. Click the image to open in full size.

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... Click the image to open in full size.

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DOGCAM
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  #4  
Old 06-27-2001, 03:53 PM
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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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  #5  
Old 06-27-2001, 05:04 PM
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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
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  #6  
Old 06-27-2001, 06:00 PM
gah gah is offline
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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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  #7  
Old 06-27-2001, 06:21 PM
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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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  #8  
Old 06-27-2001, 10:08 PM
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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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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"
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  #9  
Old 06-27-2001, 10:36 PM
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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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  #10  
Old 06-27-2001, 11:32 PM
gah gah is offline
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Question

evo
Quote:
<font face="Verdana, Arial" size="2">It sounds like there is something wrong with your truck.</font>
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
Quote:
<font face="Verdana, Arial" size="2">The gear ratios with the 3.73 are PERFECT in all gears -- nice work, Ford.</font>
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
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  #11  
Old 06-28-2001, 12:42 AM
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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.
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  #12  
Old 06-28-2001, 12:44 AM
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Wink

Quote:
<font face="Verdana, Arial" size="2">Originally posted by jwrape:
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?
</font>
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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  #13  
Old 06-28-2001, 12:56 AM
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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.
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  #14  
Old 06-28-2001, 08:42 AM
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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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  #15  
Old 06-28-2001, 09:55 AM
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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.
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Old 06-28-2001, 09:55 AM


 
 
 
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