At highway speeds (70mph) my truck is running 200 rpm more than it was before. Originally it ran 2000 rpm, now it's at 2200 rpm.

After alot of searching in the 7.3 forum I haven't found much of any info on this problem. One thread from 2004, but no fix. Just recently another member, superduty4x4 (Chase), has been experiencing the same thing and it's been discussed here:

https://www.ford-trucks.com/forums/7...ightly-up.html

Wanted to start a new thread to see if anyone had any new ideas. It started nearly 3 months ago out of the blue.

So here's what I've done, checked, and tried to correct this issue:

1. Called Brian at BTS and the torque converter (TC) was instantly brought up. I ran some 'tests' to see if it was functioning fully, and it was acting weak (per the symptoms that Brian said to look for). Per his recommendation, I replaced the TC with a new Factory Ford one. Also dropped the pan, installed new filter, flushed entire system, and replaced ALL fluid.

2. Had Edge products on the truck for power enhancements for 1 1/2 years before this started, so I removed all programming.

3. Spoke with a local tranny shop I was refered to that knows these autos really well. He stated that if I was seeing that large of an increase in rpm's, that I would being getting some codes, a flashing OD light, or something. If the pump was starting to go, then shifting would be affected.

4. Tire size, gear ratios have not changed. I have never seen a flashing OD light and no codes. Vehicle starts, idles, and runs normal. No excessive smoke or loss of power. No erratic shifting. The transmission is not acting weird in any other way.

5. Another call to BTS and Brian (as well as the local tranny guy) are beginning to think it's not in the transmission. He suggested hooking it to a scan tool to see if the gauge in the cluster is reading off. I had replaced my original CPS with a factory grey one in the spring of 2007. Bought an extra one at that time and still had it in the plastic, so I installed it to see if anything changed. I questioned about the CPS and he said that I'd most likely be seeing other issues if it was starting to go bad or malfunctioning. He said that without the truck being there, it's hard to diagnose without being able to drive it.

6. Had Ford run a full systems scan to check for sensors, codes, etc and there were NO bad sensors, NO abnormal codes, everything checked out ok. There was an update to my computer that was mainly for correcting shift patterns etc. So that was done, erasing any previous memory that the computer had. We also checked the rpm reading on the Ford scanner and it was reading the same as the dash and my digital AIC unit.

7. Ran a simple mileage check while empty (not a full tank though) and it appears to be down by 1 to 1.5 mpg. Not a full tank because I haven't had the opportunity to run completely empty (w/o a load or something in the bed).

8. Concensus I've recieved from the dealership and others has been, "Don't worry about it, as sometimes these things just happen so just drive it. 200 rpm isn't really that big of a deal." I feel like a 10% increase is significant!!

9. Haven't talked to Brian yet since taking it to the dealer earlier this week.

Thus far:

There have been ZERO change even with everything done above. It's not like it was before 3 months ago and still have NO idea as to why. I'm not going to stop until I find out, but am at my wit's end!

Sorry for the long post, but wanted to explain everything tried thus far.

PLEASE HELP!!!

 

hate to ask a dumb question but did you change your tires recently???

 

For giggles, can you install a T/C lock up switch? I know you have had the experts already talk you through it, but damn it sounds like the T/C

 

Did this start since it's been colder outside? The PCM won't lock the torque converter when the engine or trans are cold. Once they warm up it will lock.

 

#4 above: Tire size, gear ratios have not changed.

I do not have a manual TC lockup switch. However, when in UD as well as OD, it appears to be locking normally.

With the original TC in and after it was in OD, I could nail the pedal and the rpm's would jump rapidly compaired to the speed. According to Brian, this is "pushing through the TC" where it's not holding properly and getting weak. He said when performing this 'test' if the TC was holding as normal, the rpm's would increase at the same rate as the speed. The new one performs as it should.

BTW - I also checked my speedometer to see if it wasn't reading right, but it was spot on as it was before.

 

No, it was in the upper 80's up here in mid August when it first started. 60's at night. Now that it's colder, I'll let it warm up fully before driving it.

 

Ryan, I have nothing more to offer, but I am hoping this works out for you..

 

Thanks for the support anyway!

 

If you think about it real hard. If the engine is turning a certain rpm, turning the torque convertor properly, and in the same gear in the transmission, the output speed of the transmission should all be consistant.

If your tires are wearing a little over time, you will require more rpm's to go the same speed as before. But the speed should be read of a sensor somewhere and you wouldn't know that my watching the speedometer. So other than the torque convertor i have no idea. And you've covered that.

But I have one question for you... why worry so much and spend so much money over 200 rpms??

 

I know you said tire size has not been changed, but have you put on new tires of the same size. I'm sure different manufacturers have a tollerance on size and even a new set of the same size tires may not be exactly the same.

Given that.....Your speedometer and rpm should be syncronized together. Even if you put on huge tires, your speedometer will still read the same at the same rpm with small tires. In reality you'll be going faster than your speedometer says but the only way to show that would be to reprogram it to different size tires or read your speed off of a gps unit.

 

I put brand new tires on it in October 2007. I haven't even put on 10K miles in the last year (I've got a company car now). There's hardly any rubber worn on them. As of late July (last time I drove the truck empty any distance) I was running 2000 rpm at 70mph.

The answer to your question of "why worry about it" is the very reason we are all individuals and we customize our trucks. You, me, and everyone else want our trucks to be just that, "ours." Well, with my truck, I want it to be "right". Whether that's customizing, or regular operation. Now your 'right' will differ from my 'right'. I KNOW that something on/in my truck has happened to cause this 200 rpm increase. Although it's not alot, it has still changed.

My 'right' means that it's operating correctly (at least my version of correctly) and that I have 100% confidence in my truck. With this issue, I no longer have that confidence because something is wrong. So if the truck was performing a certain way, then something happens to change a part of 'normal' (in my eyes anyway) operation, then logically there's a reason for this change. A culprit if you will. And logically speaking, there's got to be a way to find out what this culprit is. That is where the part of me being very **** about things like this come into play. It's not acting like it should or like it did before, so I aim to figure it out.

Also, I'm not necessarily the only one that has ever experienced this. So if I/we (people on FTE) can figure this out, then others can benefit and we all learn.

 

Bump. Still looking for help!

 

Geez, I can't think of anything other than a false reading on the indicator.
I know you know your truck, does it SOUND any different at 70 mph?
I'm hoping that you would hear the 200 rpm, but since it's been a few months, you may not remember the sound or feel.

 

tire size won't make any difference between speedo and tach reading,the speedo just won't be accurate

did you check the speedo with a GPS to see if it may be a problem?

 

Ryan, do you know anyone with AE? What Jody suggested to me (if you haven't already done this) is to drive the truck with AE running. Once the OD locks the input sensor speed and output sensor speed should be the same, if not your OD clutches are slipping. Since you've eliminated the TC that's the last option really. FWIW my truck is still behaving the same way, but unlike you I've not had the time to mess with it.