Hello all, I have been a FTE observer for a while, and have tried in vain to find threads that i feel address my issue. Looking for help from the Tranny guys in the forum. I recently moved from new england to Nashville, via SC. I have a 2001 F250 5.4, 4R100 automatic with 75k. I towed a 18X8 enclosed trailer and a full bed. The truck had a Kelsey brake controller when i bought it. I believe I'm the third owner, I bought it with 50k on it, and i think the original owner had a trailer. I had attempted to install a extra capacity vented trans pan on prior to my trip, however I noticed that of the 20 or so bolts in the pan, at least 6 had been over torqued, and the threads were damaged. So I abandoned the project and went stock pan. Changed The ATF to Merc V, or at least the 7 quarts held in the pan.
Now to the problem. On the long haul I traveled with the overdrive off as per the recommendation of the members of FTE. When heading up th steep grades the rpm's would hit 3500 in the lower gear. When traveling over 70 mph I noticed a sound that resembled a plastic bag rustling in the wind. It happened every time the trans hit 3200 or so in high gear. So I tried to avoid it as much as possible.
After the trip I have noticed when the tranny down shifts to pass someone the rps are around 4000 and it just doesn't seem as responsive. Any thoughts out there in FTE land?

Thanks

 

I have several thoughts.

First, the recommendation to tow with the overdrive off was just to get you to burn more gas. The transmission was designed to tow in overdrive. If it stays in overdrive without frequent downshifts you should tow in overdrive.

Second, an extra capacity vented pan is only useful to use up extra money. It doesn't help the trans. On the other hand it doesn't hurt the trans, either.

Third, when changing the trans fluid you should either have removed the torque converter drain plug to get another 8 or so quarts, or use this method: Transmission Fluid Change.

Fourth, those RPMS are normal for a 5.4L, or even for a 6.8L V10. These are high revving engines. That's where they make power.

 

Thanks for the response, however I have not dropped the pan due to the marred threads I found. I am a single vehicle household and was trying to avoid a large project a few days before a long trip. I am primarily concerned with the 600 to 700 rpm increase while passing and the seemingly sluggish response at those elevated rpm's now, when compared to my pre-trip memory.

Did I do damage on my trip? What was the "plastic bag in the wind" noise. And being a 5.4 V8 I do not have a trans temp gauge, so I have no clue what kind of temperatures I reached in a 15 hour stretch towing a 9k trailer and a bed full of tools.

 

It's hard to say, but you're sure that there is a difference between now and before the trip? Remember that an automatic transmission is just like a manual in the regard that it has fixed ratios. Of course the torque converter can add some slop to this when unlocked, but it shouldn't be hugely variable either.

I know that the torque converter could unlock when you downshift, and I would guess that if it were failing it could allow more slip. Has your O/D Off light been flashing at all?

 

No, unfortunately the only evidence that I have is my gut feeling. After driving the truck for a year a man knows the sounds and feeling of his truck. Then the long haul and it just feels "off ".

It has developed an intermittent idle/rpm issue on start up but i think that is a different problem.

 

if i remember is there not a inspection plate that can sometimes come loose and cause a rattling sound? shot in the dark here but it might be what your hearing.

 

From experience I would say a lose of power at higher RPM and a funny noise you are looking at a plugged catalytic coverter. It just happened to me and the more power I asked for the Higher the rpm went and the less power I had. Check you converter. With the truck Idleing go to the exhaust pipe and listen to the pulses coming out. Mine were very inconsistent.

 

Both good suggestions, and I think more likely than a transmission issue.

 

When Mine plugged the blocked converter caused the heads to get so hot that the motor was pinging like crazy at the higher rpm. My guess is that is what you are hearing that sounds like a plastic bag.

 

I checked the exhaust sound at idle. Everything seems normal.

Also when the rps spike to around 4200 during a "pass" the engine roars but the truck doesn't seem to move out the way it used to.

 

I would still suspect converter with the info given.

 

Did you put the same type of oil back in the trans that was in it ??
maybe you added synthetic oil to non synthetic and it's braking down and causing it to start to slip

 

That's an old myth that simply refuses to die. Synthetic and non-synthetic are completely compatible; they can be mixed without fear of any issue.

 

Not only is the mixing of synthetic and non-synthetic perfectly acceptable, if the trans was slipping it would be complete junk in a VERY short time. It takes 2-3 seconds of slipping at power to completely destroy a clutch. Then there will be black trans fluid and BIG shifting issues.

So this was not just one, but two myths perpetuated by one post!

 

So is this something i should be concerned about and take proactive steps? Or if it is the Torque Converter and I wait until it becomes a non negotiable fix, will I cause more damage. Then spend the money and effort to helicoil at least 25% of the pan bolts and get to the issue?

what do you guys think?