k-stater88

the fact that i can drag that trailer around in 5th gear with little effort under 2,000 rpm's and under 50 mph, leads me to believe the ECM isn't right, especially watching the gas gauge. I really think a tune might fix it. When I test drove the 3.31 and the 3.55 on the lot and my trailer, the 3.55 would do everything mine would do, only a gear higher. When mine was running great in 4th, it would do it in 5th and at 4 mpg better. that spread shouldn't make that much diff.

acdii

Rear end gearing should not make any difference in how the truck cruises while towing other than the engine RPM at a given speed. The lower the gearing, the higher the engine RPM. The lower gears help move the rig from a dead stop as it puts the engine RPM up towards its power band. That's why 4:10 gearing in a truck makes for a very good tow rig, but a poor speed truck. I had an F350 with 4:10, the engine was up around 2100 RPM at 65 MPH and sucked fuel. I swapped to 3:73, dropped RPM down to ~1800 and gained 3 MPG, but still had what it needed to tow.

The higher the gears, the greater the top speed at a given RPM, the downside is, the transmission needs to drop to a lower gear to get the engine into the power band. That means for a 3:55 geared truck at a given speed and gear, the 3:31 and higher gears would need to be in a lower gear to get the engine in the power band.

However, that should have Zero effect on towing capabilities, or speed. You will still be able to go 70 MPH with 3:31 gears, just at a gear lower in the transmission. Once you reach that speed, and are cruising, the truck will try to upshift to the next gear, but as soon as it detects loss of torque in that gear, will downshift.

This is all done via the computer, so if the truck is having difficulty reaching a speed pulling a trailer, regardless of the gearing, then there is a computer glitch, or a faulty sensor somewhere. I does not matter what the rear end gearing is, the 5.0 has more than enough power to pull anything it is rated for, and if it doesn't, then something is faulty.

Now what I am wondering, I don't remember which thread I read it in, but the poster said he had the pedal down, and could not go above 50 MPH with the trailer attached. What I am wondering is if the truck detected the trailer or not. Unless the truck detects a trailer, how would it know it was pulling something? Could it be related to the tow/haul mode, and has it been driven not in T/H? How do it know?

SixShooter14

yeah, I agree with the computer problem. somehow, the system is limiting the available power.

maybe put it in "M" without "T/H" and keep it in as low of a gear as possible. Remember, redline is pretty high with the 5.0L and it likes the RPMs.

Would also be interested in towing without the lights plugged in. Just hook the ball and take off in the normal NOT "T/H" mode.

k-stater88

I tried all that. I unplugged the trailer. I ran it in sport mode, t/h mode, regular mode and nothing changed in pulling ability. If it is a problem w/ ford's program, which they said was good to go, a tune should fix it.

SixShooter14

Man, idk...

If you're close to a good tuning shop, then you could have them work on it and test it until they get it right. Or do a mail-order tune then datalog and have them adjust it to be just right...but of course you'd have to pay them. Which I wouldn't blame you for not wanting to do.

It's probably easier to trade it in or sell it and get another more suitable to tow your load. Then do a tow while test driving it if possible...no doubt a frustrating situation.

jcb206

Absolutely do not trade it in. Have them fix it. Take the mechanic out with you towing a 3-4K load and show him that it won't get to 50+ mph. See if they have a used 5.0 on the lot or 5.4 and show them how it can reach 65 easily. Have them fix the programming and if they can't then Lemon Law it.

I don't care if the truck had 3.15 gears, it should tow under 5k without a problem. Interesting that this problem is only happening to 1 engine with 1 certain gear ratio. The engine can handle it, so it must be the programming.

As someone that had a truck with problems, I feel for you guys and gals. It is not a fun thing to deal with. The easiest thing to do is trade in and pay for the loss for a few years but hold out if you can. This will get solved as more people realize the problem.

Good luck.

SixShooter14

I agree, trading in or selling should be the last resort. If nothing else, it just passes the problem to someone else.

Seems like the dealer Service guy knows there's something wrong and they can't fix it. Then I'd think they should have to replace it. Or at the very least replace parts until it's fixed. AND provide you a loaner vehicle while it's worked on.

Definitely research the lemon laws for your state and see if you can get something done.

k-stater88

UPDATE *

I decided to pull the trigger on a tune, but I just needed to check with one different dealer, one last time to make sure there wasn't something wrong.

This fourth dealer noticed right off the bat that my PCM was 6 updates behind. They couldn't believe none of the other dealers were updating it. They said it was so bad it took 3 hours to get it caught up. They also fixed my door problems (they claim...i'm picking it up in an hour). They noticed that the seal had been crushed from the other dealers messing with it.

I'll report back if this stuff got fixed. If so, I found me a new dealer for life.

BRUTE448

are you going to report back on if the updates worked, before you get the tune?

ive seen a few threads in the 15'+ section about 15/16' 5.0's with 3.31's with your problem.

best of luck with this!

acdii

Now that is double Facepalm worthy!