Now this truck does have BFG MT KM2's in 286/70/17 that were on it when I bought it. I checked the gearing and it is 3.55. I have had to replace a couple coils but other then that the truck runs good and no engine codes. I even took it to our local ford dealer and had them check it out. The only thing they cam up with was "a broken spring in the throttle body" I figured they were talking about the throttle position sensor as the only other spring in the throttle body that I know of is the throttle return spring on the throttle plate. So I replace the TPS and no difference. Could the extra tire height and weight really be causing the power issues. Cause it won't even spin the tires on dry pavement not even for a bit. Or is this "normal" behavior for a 4.6 in a truck.

Thanks
Bob

 

Your really funny!
Sure the larger tires takes away from the final gearing but the truck still does not have enough torque to make a Hot Rod out of it..
The truck weighs some 5300 lbs plus your weight, gas and any other weight on the truck.
The motor is 280 cu/inches; hardly a torque monster at the low RPM point the converter locks up.
The torque maxes way up over 3200 rpm not down low under 1500 rpm. Big difference.
This displacement is smaller than an old Mustang of the late 60s/70s with a small block.
My 02 is pretty torquey but it has a modified torque converter and standard tire size for towing and has 248,000 miles to boot.
I bet you would give this one a lot of credit for pulling 12,000 Gross Combined weight it has done for, me pulling a loaded race trailer..
Good luck..

 

Thanks for the reply bud. I realize this thing is by no means a hot rod but c'mon shouldn't it at least attempt to chirp the tires when I stick my foot to the floor from a stop? Another example,,,i was backed up to a railroad tie a while back. rear tires touching the tie and it wouldn't pull itself up over it until i put it in the low side. Is that normal for these trucks?? I guess that is my question. Does this seem like normal power levels for these trucks or is there maybe an issue with the converter,,,tranny,,timing. I had a 300 inline that would have owned this thing

 

I just explained to you the converter goes into lock up at low rpm where the engine is not making a lot of torque.
Engine torque begins the build fast above 2500 rpm and peaks over 3200 rpm.
Naturally you have no good torque at the low rpm.
.
Trying to compare to a 300 inch larger low speed engine that makes it's torque down low is not my idea of a proper comparison of the two.
Do you still disagree on that basis?
If yes, you need some other truck.
Good luck.

 

sounds familier. I had a 98 F150 with the 4.6. all stock but think the tires are better than stock. it had no problems in spinning the tires. now I have a 2001 with the 5.4. it wont spin the tires, and I have seen other trucks with stock 5.4s able to spin the tires easily....................... and my truck has no codes, and it never has run up to par

 

Exactly,,,I have a 1996 towncar limo that weighs over 5000 lbs. It has the NPI 4.6 and highway gears and it has more power then this truck. Something has got to be wrong

 

Besides minor differences between trucks and years for torque production vs age etc.; you must understand for example a Mustang altered for drag racing normally will have a higher stall torque converter replacing the original.
Why:
It's stall speed is raised closer to the engine's peak torque RPM.
Therefore more torque is available to the tires at the time the converter hooks up .
Again, in a truck application the converter stalls too low for the torque available from the engine on most trucks.
Only way to get more torque to the rear wheels is to lower the rear gear ratio, increase the converter stall speed and or add engine torque.
As far as codes, sure, if there is a fault that affects engine torque production, you may see a before and after effect from a repair.
There are other things that affect engine torque such as the intake air temperature, humidity, barometric air pressure. All have effects on engine power.
One sensor that can affect overall power off idle is the IAT or intake air temp sensor. If it is at one limit that tells the PCM the temperature is warmer than the average, that usually pulls timing and some fuel out causing less torque production and it does not set a code because the sensor is still looked at as being within limits of the system design by the program.
So you have tolerances stacking up for or against in any system that has self control.
Only way around it is to look at every operation for working limits, then do whatever you need to peak performance.
Most have no time, knowledge or capability to do this on a system already working within it's design tolerances.
Bottom line is you live with the average you happen to get or spend effort to change it.
Last reply, good luck.

 

I suspect that Bluegrass may be right. but in order to do what he is suggesting you need a scanner. Not a Code scanner. and he is right about it taking time. Ive had my truck on a scanner. and I may spend more time looking, but eventually, Im going to get rid of my truck.

 

One thing about stall speeds..... the stall speed is affected by how much torque the engine puts out to start with. if the engine isnt running right, the stall speed will be lower.

 

Absolutely, converter stall is a variable that depends on engine torque, gear ratio, and weight.
The ability to spin a tire depends on tire traction, how much weight is transferred to the rear from inertia of moving forward suddenly vs how much torque is available before the tire loses traction.
You see all the variables already such that you cannot compare one vehicle to another without the conditions being the same.
Certainly in production assembly line vehicles the tolerances of vendor parts are all over the place.
If you happen to get a build that stacks all these in the direction of hot performance , good for you and then another might get stacked to other direction and be called........ a dog.
I tried to offer the basis for torque production by offering known facts.
In these trucks, the 4X4H is not meant to make the truck a stump puller but to offer increased traction of two extra wheels.
The transmission is in the same gearing as it is in 2wd. Why would anyone expect different?
Going to 4x4L is a different ball game with a huge step up in overall numerical gearing, a change in shift schedule to put the engine in it's higher rpm range where it IS making more torque.
You cannot discount science in these comparisons.
Good luck.