5.4 vs 4.6 mpg & reliability - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 03-10-2002, 07:43 PM
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5.4 vs 4.6 mpg & reliability

I am in the market for a 97 up half ton 2wd daily driver. I was wondering what the mileage differences were with the two V-8's. I probably won't be pulling much with it since I have an older pulling truck so my main concern is mileage and reliability. I have heard alot of people complain of their 5.4's piston slapping. Is this a common problem? I don't want to buy a newer truck just get more problems. I am seriously considering a 96 just for the 5.0.

Also I am curious about the new trannies. How are they holding up? I have always had a stick and don't mind to shift but I was thinking about getting the auto (4e70w I think?) this time. However if they aren't very strong I would rather keep a stick. Any help would be appreciated.

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post #2 of (permalink) Old 03-11-2002, 07:48 AM
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Re: 5.4 vs 4.6 mpg & reliability

If you are going for a commuter truck then 4.6 would be your choice. I have the 5.4 in a 2000 F-150 and so far have not experienced any problems with the motor besides being a little thirsty. The piston slap thing is common for the Chevy Big blocks also, my buddy took his in to get it looked at and no harm is being done when this happens. It goes away when the rings heat up. But like I said it isn't happening to mine. I haven't opened the hood on my truck but three times and that was to put a K&N filter in, look at my new radiator (assembly line snafu, nothing was wrong), and to wash it after a little playing in the mud. I think the mileage difference between the two is only 2 mpg. We have some friends with well over 100k and zero problems. Do try to get a 1999 or newer because of major power increasement in the motor.
As for the tranny's I haven't heard anybody have trouble with them yet. We are brutal to them here at work and they don't even bat an eye at the abuse. They are all automatics also. But if you want a quick little booger get the 5.4, I haven't lost a drag race to a NEW $hitvrolet yet, Dogs I mean Dodges aren't even an issue. I know they weren't built for this but it sure is fun waving "by by" as I pull away [img]/wwwthreads_images/icons/shocked.gif[/img]. This is with 305/70/16 tires and a stock 3:55 rear. Good luck with whatever you pick.

post #3 of (permalink) Old 03-11-2002, 01:04 PM
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Re: 5.4 vs 4.6 mpg & reliability

Thanks for the info. I will probably try to get a 99 or newer now. I am glad to hear the good news about the trannies. I hope I will like an auto!

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post #4 of (permalink) Old 03-12-2002, 09:06 PM
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Re: 5.4 vs 4.6 mpg & reliability

so what kinda mileage DO you get with the 5.4? and wtf is piston slap? i might be in the market for a newer 2wd daily driver myself this summer but if it doesnt get much better mpg than the BRONCO, forget it, cuz i love the ol gal [img]/wwwthreads_images/icons/tongue.gif[/img]

if i'm going to get rid of my awesome four wheeling ability then i at least want something FAST, so i'm sure i'll get the 5.4.

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post #5 of (permalink) Old 03-13-2002, 09:41 AM
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Piston Slap

"Piston slap" is when the skirt of the piston is dragging, or "slapping" on the side of the cylinder wall.
In an ideal situation the piston never touches the sides but is held away by the rings.
However, with age the clearance between the piston and wall opens up,
and causes the piston to wobble in the cylinder.
When the engine is cold it's worse.
Aluminum (the piston material) has a much higher expansion rate than iron,
and closes the gap when operating temperature is reached.
The newer engines have increased clearances to lower friction losses in order to boost gas mileage.
Seems like a lot of newer engines have this malady now-a-days.

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post #6 of (permalink) Old 03-13-2002, 08:10 PM
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Re: 5.4 vs 4.6 mpg & reliability

Muddy, I get 13-14 mpg. This is freeway and side streets combined. Please do remember that when I drive its FLOORED then BRAKES and so on and so on. I think a Lightning would have fit my personality better but, I still need to throw a dirt bike and camping gear in the bed every now and then. Looks like my girlfriends 1999 Mustang GT is going to be traded for the new Vette and Firebird eater ....390 hp 2003 COBRA. I'm picking up OT and so is she at work. Can't wait!!!

post #7 of (permalink) Old 03-19-2002, 09:34 AM
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Re: 5.4 vs 4.6 mpg & reliability

My new 5.4 F-250 is starting to get better 'economy" First 1000 miles was 9 - 10. Now it's bumping up to 14.
The 2003 Cobra is awesome! We tested a couple here in Dearborn. Save up for more tires, and practice walking like you're handcuffed! These things are begging to be opened up on the road. THe Police won't like them near as much as you will...
post #8 of (permalink) Old 03-19-2002, 02:53 PM
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Re: 5.4 vs 4.6 mpg & reliability

Ron bo, how do I become as lucky as you to test drive the new Cobra's before they come out. My truck also needed some break-in time to acheive todays mpg. Do you have the SD body or the F-150 style?
post #9 of (permalink) Old 03-20-2002, 01:09 PM
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Re: 5.4 vs 4.6 mpg & reliability

Many years in night school, followed by a "lucky" break to be hired into Ford. Some of us engineers get together and "compare" our program vehicles (I'm on the Explorer programs). It's a nice chance to experience some future stuff.
I got the Super Duty. I owned a 1997 5.4L F-150 Flareside Off-Road while I was redoing my Bronco. I hated the F-150 so much that I vowed to never buy another new truck again. I do like the SD much better than the F-150, but I still do not like the transmission (E4OD).
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