99 f150 4X4 DD build
 

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This is my new daily driver a 1999 f150 4X4 xlt with a 4.6 titan and 5 speed manual transmission.
I just picked it up 3 weeks ago and so far I've changed the spark plugs and wires, changed the rear diff fluid to mobile 1 75w 90, changed the oil to mobile 1 5w30, converted to electric fan and m3 style mirrors. My current goal is 25 mpgs

Yesterday I replaced the fluids in the front diff transmission and transfer case to mobil 1 synthetic fluids and added a lawn edging air damm and according to my ultragauge it gained 2 mpgs
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My next mod will be tires it's currently running on bfgoodrich all-terrain t/a 265/70 R17 but I want to switch to a highway tire with the lowest rr possible

I have always had good luck with Michelin LTX M/S2 or the new LTX Defender on a variety of Chevy and Toyota trucks. I have run LT235/85R16 and P245/75R16 with good success, both producing good traction and good MPG. Provides great traction on road (especially in inclement weather) and fairly good traction offroad (better than you would think) as long as you stay out of deep mud. If you go too wide for the weight of your vehicle you will be more likely to hydroplane and probably won't like the traction. I put 265/70R16 on my Tacoma (from my wifes 4Runner when we got it) as a stop-gap and do not like the traction compared to my LT235/8R16s that used to be on it. Her car now has better traction, getting new 245/75R16s (identical diameter and tread pattern, just different widths).

Do you know the rear end ratio or how many RPM you are at at 55 MPH? One reason to switch to a taller tire is to reduce the RPM for a given speed, but I have found this effect helps less than the lower rolling resistance so don't compromise your tread pattern for the sake of diameter (been there done that with 255/85R16). A good tread pattern in tall and skinny is your friend for good traction and good mpg.

At least that is my experience with five 4x4 vehicles and trial and error with more tires than I can count, I am sure others may have had other experiences.

At 60 I'm running about 1950 rpm but a set of 2.73 gears should get me to around 1400 rpm. I'll have to check if they come in 17"

1950 RPM at 60 MPH is a little better than where my Tacoma is (2000 RPM @ 55MPH w/32" tires). You can find 245/70R17, 245/75R17, and 235/80R17 in Michelin LTX Defender or MS2. Some of those sizes are in LT only, not P rated. Were those lower gears offered for the front differential as well? I know with the Tacomas and Chevys you could get much lower gears for just the rear than you could for the front, thus a 4x4 was somewhat constrained on the lowest ratio available. I have 4.10 in my 1994 4x4 Diesel Suburban project that is ongoing to replace my Tacoma, I plan to swap those to 3.42 which is the lowest ratio I can get for the front.

The mechanic at my job says rear gears should work in the front and if not I'm sure I can just use 3.08 in the front and only use 4wd if I get stuck in mud or snow.

I've been wanting to remove my front axels anyways they're always spinning even when not in 4wd they're bolted through the front hubs like a fwd with no lockers available and I think I can get around just fine in 2wd

https://m.tirerack.com/tires/tires.j...omCompare1=yes thinking about getting these tires but don't know how long winter tires will last driving year round?

I have to ask... what are you hauling around every day?

Well currently nothing its my dd while I'm swapping the motor in my Saturn. I am however working to start a business.

Oh. As you can see I have a pickup too but it's a pig and using it as a DD without making it work hard would be expensive. I suspect no matter how well you tune it up it'll end up in the teens mpgs most of the time anyway.

Do you need LT rated tires? I don't think the compound used to make the LTX winter would just melt away in the summer, i would guess it is very similar to the LTX M/S2 with a few more additives.

I assume you are looking at those because they are less expensive and have the rebate. Just throwing these out there if you don't need the LT rating.

https://www.tirerack.com/tires/tires...LXI2&tab=Specs

https://www.tirerack.com/tires/tires...LXI2&tab=Specs

I don't do much heavy towing at the moment but would like the option to and I would prefer not to go with any smaller off a tire but the price sure looks tempting and the tread patern looks good for fuel economy

Had a milestone moment I just filled up and finally broke 20 mpgs! 20.15 to be exact in a truck that's only rated for 14 mpgs combined and I still have so many mods I can do !

Your truck has a center axle disconnect so only the axles spin in 2wd. The differential and the front driveshaft do not turn. I doubt it is worth the trouble to remove the axles.

Finally got tires https://m.tirerack.com/tires/tires.j...omCompare1=yes
But I didn't pay $250 each I got a lightly used set on Craigslist with about 75% tread left for $100

Get a Scangauge on that beast so you can closely monitor coolant temps, start experimenting with grille blocks. It's getting to be winter so you will probably be able to get away with blocking the whole thing while it's cold - faster warmups, less aero drag, win-win.

I saw how you picked up 2 mpg when switching over to an electric fan. Nice.

I went fan delete but couldn't tell an fe difference. :confused: There must be one though.

I have a ultragauge it usually runs about 201-206f with the upper grill taped off and around 206-215f with the lower grill blocked also. The fan made a huge difference both in warm up times and engine load. I have a thermostatic switch that turns the fan on about 217f so it's almost never on

I'm also slowly building a aerocap

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Seems like a waste starting with a 4x4 and ripping the guts out to make it more fuel efficient. Would it not be more practical to sell/trade the 4x4 for a 2wd model? Around here a 4x4 would go for double an equivalent 2wd in the used market.

Swapping/trading for a 2wd you would likely make a bit of money on the trade and already have a truck that is lighter, lower, has less moving parts, smoother front suspension, and likely a taller axle ratio.

Being practical I need a 4x4 to get through winter I just can't help but think how much more efficient a 2wd would be. I'm leaving it 4x4 for now and will work on other ways to make it more efficient

A couple weeks ago I installed a Kats circulating water heater but it's not really circulating the coolant the lines get warm up to about 6" from the pump but that's it I'm thinking about adding a pump to help it. Any ideas or suggestions?

The main thing is that you install the circulating tank heater LOW in comparison to the engine. The heated coolant has to be able to flow up vertically via natural convection. Pretty much the lower you can mount it, the better it'll work.

Also, if you have it installed in series with your heater core, make sure your heat is set to on when you turn off the car. Most cars have a heater core bypass valve that closes the heater core coolant circuit if the heat isn't on.

I mounted it flat below the radiator tapped into the lower radiator hose and into one of the heater hoses

I'm also thinking about a oil pan heater and a small 250 watt ceramic heater for inside the cab

They're what I run on my truck. But MPG is better with the closed shoulder A/S model. I lost .75-1.00 to annual average, easily.

Be sure to check date code on tires. Five or more years (seven) is getting near end.

Biggest problem with pickups is steering.

Bilstein 4160 shocks, first, to help it track.

Then, from new steering column shaft, all the way out to new tie rods.

All the aero in the world won't offset "wander".

Pickups have bad road feel, new. And being to read the road and adapt is big. One needs to be able to distinguish between road problems and wind problems.

A pickup where the driver can't make these distinctions can't accurately tune the suspension, which they all need. They'll go down the highway sawing the wheel and the truck is at mercy of ruts and adverse wind. Bye-bye margin. It's all sucked up as extra HP demand, whether at low speed (rolling resistance) or high speed (aero resistance).

IOW, there's no way to get a clean baseline.

Tire pressure according to Load, alignment and no brake drag are great. But if one wants best MPG, it's steering first, suspension tuning second, and aero last.

Addco and Helwig both make replacement anti-roll bars. Is there one on rear?

Sort out what you'll do with drivetrain, first. Because after zeroed tracking problems comes wind effect on body. Where some (possibly) different anti-roll bars will isolate steering from crosswind.

The aerocap WILL increase sail area.

Load the truck, and a tired old front end will steal your efforts.

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I'm going to have to get on that so far the only thing I've done suspension wise is loosening the torsion bolts to lower the front 2" and I think I might have a bad wheel bearing on the front.
On a side note I got my coolant heater working it was laying completely flat and not moving any water I twisted the bracket so the out line is facing more upward and now it works good

Small update I got a couple parts ordered from American muscle
https://www.americanmuscle.com/black...ghts-9703.html
https://www.americanmuscle.com/bellt...-9703-4wd.html
I expect a small increase in fuel economy and a large boost in safety. It's dear hunting season here and a lot of them run onto the road the projectors should help me see them better and the lowering kit will make the truck more resistant to rolling in the case of sliding winter is coming. Also my daughter has a hard time getting into the truck and a lower truck is easier to load stuff into.
Looks are just a bonus ;-)