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i regularly drive my ‘92 F150 5.0 without any noticeable issues. I bought a 7X16 double axle enclosed trailer I’ve been wanting for a long time. Driving it home with the trailer it had shown running quite a bit hotter than usual and was pathetic in regards to power. I (with a 5sp manual) struggled to reach and maintain 50mph in 4th. Forget about 5th. I feel this truck should’ve had no issues pulling this trailer empty. Suggestions? Could a clogging converter create these symptoms?
Before pointing fingers at potential problems a few key questions:
1. Axle ratio?
2. Tires size?
3. Any other significant modifications?
The 5L engine is known for little low end torque. Driving around empty may not reveal the true gutless nature of this engine when you have absurdly low numerical gearing. Add a little weight and frontal area the true nature comes out very quickly.
Best I can make out on the diff tag is 373. Factory size 235x75-15’s and no mods other than a K&N air filter. My worn out ‘93 F150, straight 6, and 5sp with 31x10.50-15’s on the rear did a far better job pulling it today and it has over 500,000+ hard miles on it. Same rear gear. (??)
Ford never installed 3.73 gears in the OBS trucks. I would lean towards 2.73, which is what I was alluding to earlier. Obscenely numerically low gearing will strangle the 5L.The 4.9L makes more torque in the lower RPM range than the 5L engine (both stock).
Check the sticker on the driver side b-pillar for the axle code to verify what the truck left the factory with:
If it is 2.73 that is the root cause of your issue. For that matter anything less than 3.55 is going to exacerbate the issue. Some suggest 4.10 as a starting point for the 5L trucks. They like to rev.....
The 5.0 motors work best at 2500rpm or higher just in case you were driving it like your I6 truck, the powerband is almost the opposite with the V8 just coming into it when the I6 is almost tapped out. But that said definitely check fuel pressure, base timing setting, and for good exhaust flow, if any of these are not right the truck will be handcuffed.
Now that we know you have a reasonable axle ratio it's time to check the other items off the list. As Paul stated check the fuel pressure, at idle and under load, base timing, etc.
How old are the plugs, wires, cap & rotor? How about the filters?
Basic maintenance items can make a huge difference.
Plugs, wires, cap & rotor replaced prior to a trip about 2000 miles ago. Recent ignition module on the fender well, new coil and module in the distributor. Fresh K&N air filter. I’ll take it to my buddy’s shop tomorrow for fuel pressure test. Fuel filters fresh prior to my purchase of the truck 1yr ago. All that’s been done is one reason I’m wondering about the catalytic converter. 193,000 miles.
You're in overdrive. It'll never have enough power on the highway in overdrive pulling a trailer.
I understand that. My speed/rpm example was going to work w/o the trailer. I'm not even concerned about an overdrive gear when it struggles to maintain 50mph in 4th with the trailer.
I understand that. My speed/rpm example was going to work w/o the trailer. I'm not even concerned about an overdrive gear when it struggles to maintain 50mph in 4th with the trailer.
Sorry, I was thinkin you had an automatic. Even so a 302 isn't a good towing motor unless it's geared down to the max so it can rev.
03-11-2019, 10:37 AM
