Hello FTE's. Looking forward to using this site more. Hope you all can help me. As I typed above I have a 2005 F250 King Ranch 4x4 Crew Cab swb. White/ tan. Oh yeah. Diesel, automatic but the trucks I have seen like this usually are so it may have gone without saying...but just in case. Pretty well factory. A few cosmetic upgrades but mechanics are all stock. Truck has 73,000 miles. Warranty just dropped last month. I'll post some pics as soon as I figure it out.

I'll apologize for the length of this. I want you to know everything I know about this issue so far.

For the last two years the transmission slips when the outside temp. gets over 90 degrees. This doesn't happen all the time but I notice it the most if it is hot outside, if I have been driving for a while in town or on the highway(it doesn't matter), and only taking off from a stop. When I take off the engine rpm's go way up as the engine rev's but the truck slowly moves forward. I'd say about 40% power from take off than normal. As the truck reaches the shift point into 2nd normally it shifts just fine and "usually" it shifts fine through the rest of the gears. (side note; I have heard it slip maybe a few times from 2nd to 3rd but not too many times, a couple times while pulling a trailer, a couple times without pulling a trailer, both times with high outside temps.) Here is the tricky part. I can go one block and stop or 20 blocks, stop and go and sometimes it will slip again and other times it shifts like it was a brand new truck. It has been over 100 degrees outside and I can run all over town or down the highway and it not slip at all. Never colder weather. Actually I don't think it has ever acted up when it was below 90 degrees.

So I have taken it to Ford 4 times in 2 years and they can find anything wrong with it. It throws no codes. I changed the trans. fluid/ filter last spring even though I didn't think that was what it was. With the mileage I figured, why not? Fluid was nice and red and clean just as it should be. No difference from the weight of towing or not. It still sometimes does it and sometimes not. Same results as I stated above. I have a buddy who worked as a Ford mechanic for 20 years before running his own successful mechanic shop. He doesn't know what it is. He is not convinced it is in the transmission since it is intermittent. Maybe a sensor or more like a shifting issue in the computer but no one seems to know. I agree if the tranny is slipping it should not only be doing it more than occasionally but it should be getting worse. Actually after 2 years of this I would think it should have gone out by now. It's severity is no different today than when it started.

Oh and the first time I noticed it slipping was 2 years ago I was pulling a BobCat Skid Steer, towing weight about 9K. I would say about May or June'ish I hauled it the one way about 75 miles and it slipped twice during the trip. Hauling it back home that afternoon it didn't slip at all and it was warmer out.

Now that it's cooling off I my not experience it again until next summer but I don't like driving a truck that "could" have a problem. Especially since my wife and I are wanting to travel with our 5th wheel from Oklahoma to Washington. I don't trust it now but before I trade it off I thought I would give you a shot and get your input. Maybe someone out there has seen this before and has a solution. I don't like parts changers. I'd rather troubleshoot it for a while and fix it once as opposed to paying a shop a gob of money to guess. Sorry this was long. I wanted to make sure you had the entire story to help you help me diagnosis this problem. I have no problem answering more questions if needed.

Also I thought about getting a tuner to change the shifts points but I didn't know if that would work. I appreciate your all's help in advance.

JH

 

If the trans is slipping in 2-3 seconds the forward clutch will burn to a crisp. This will turn the fluid black and it will stink. If you keep driving like that the clutch will weld itself together and the trans will be essentially undriveable.

Since you don't have these symptoms I don't think the trans is slipping. It is more likely that something else is happening.

I can think of two things. One is that the engine fan could be turned on. It takes a lot of horsepower to turn the fan with the clutch engaged. This will cause a very noticeable lack of power. It also generates a HUGE amount of noise, which many people interpret as the engine revving much high than normal. It isn't, but it sounds like it is.

The second guess I have is that sometimes the trans isn't returning to first gear. When starting in a higher gear there is a big loss of power.

The best (only?) way to diagnose this is with a scan tool that can look at live data. When it happens you need to be looking at the transmission gear ratio, the engine and trans temps, the parameter that shows if the fan is engaged, and maybe the fan speed, too.

 

The fan certainly makes since. I have that on other posts but wasn't sure. It would explain why it only happens when it is hot outside but it doesn't explain why sometimes it happens and sometimes it doesn't. Even when it is really hot outside there are times it won't do this. Also you said it will seem like the vehicle loses power. When this happens it feels like it takes off with more than 50% loss of power. Like it is falling on its face. Would it be that much?
On the transmission...I can pull into a parking lot,we'll say a convenience store, leave the truck running, back out of the spot to leave and when I put it in drive it will take off forward as it it suppose to. Then when I pull up and stop at the road and then accelerate to pull out all of this can happen. Not everytime though. I guess I may have to invest in a live scan tool.
FYI-when this happens the gauges are normal. Engine and trans. Temp. Gauges. Everything.

 

I think Mark meant that the fan just happens to kick on with the fan clutch locked as the truck is shifting, or immediately after. It doesn't happen a lot because the timing has to be just right to make it feel like the transmission is slipping.

When it comes to the torqueshift transmission (5R110), Mark will know. He helped design it.

 

It's just blowing my mind that it only happens sometimes. I despise intermittent problems. I once drove it a couple of hundred miles with the temp. over 100 degrees and it never happened once. Next day while 95 degrees outside I drove it @4 miles and it messed up. What bothers me the most is this issue has about got me broadsided. Which scares me to think if my family was with me when this were to happen. From what you are describing it could very well be the fan but I mean it has no power when this happens. Believe me I won't discount anything ideas. Especially from someone with knowledge like Mark. I just can't imagine a fan even locked in can cause a diesel truck in 1st gear to be so helpless. It feels like a have a manual trans. stuck in granny gear for 2-5 seconds. its that slow. I will say it hasn't happened longer than @5 seconds but 5 seconds is a long time when trying to cross a 4 lane highway. If you all are thinking it is more likely the fan I don't have a problem changing it.

 

Have you ever had the transmission serviced with a hot flush at the dealer? If you haven't I would and make sure they change the external filter.

 

I have never had the transmission hot flushed. I would have hoped that after 4 trips to the Ford service dept. they would have suggested that if they thought it would help. Is there a way to manually engage the fan clutch to see if it shows the same symptoms and if so, how?

 

Never assume the dealer is going to suggest a particular service, you have to be proactive. I took my truck in for the transmission service and after looking at the work order i discovered they had not changed the external transmission filter as i had requested. In fact the service advisor told me that my truck didnt have an external transmission filter, that is when i took him out and showed him that i do in fact have one.

 

You would need an IDS scan tool (or equivalent that enables active commands) connected up to the data link connector and active command taken of the FAN_VAR % data from 0% locked in at 100%. 100% duty cycle means the fan clutch is completely engaged. With the engine RPM raised to 2500 RPMs and FAN_VAR at 100% duty cycle, FAN_SS (the fan RPM) should increase to well above 2800 RPMs. When it's turning that fast, it sounds LOUD.

 

AE can command the fan to 100% duty cycle

 

Ok. I don't have an AE or any other scan tool to do this so I had an idea. Since this problem only happens when it is hot I wonder if I can trick the sensors by making the engine just hot enough to make the fan kick on. I know all you are going to think this is stupid but hear me out. First of all let me say like many of you out there I have been working on cars since I was a kid. Rebuilt my first engine when I was 15...successfully...but I am not an expert on this truck like I know someone you are. My idea is putting a better temp gauge in so I can see what's going besides the dash gauges. Then with the truck running and keeping a close eye on the gauge block the radiators air flow temporarily to raise the temp of the motor. If its the fan I would think it would kick on once the temp got high enough. Hopefully before it gets too high. Before the temp reaches the critical point and the fan has or hasn't kicked on unlock the radiator. I know it is dangerous but I wouldn't do it without help and watching it really close. What I am not sure of is I noticed you all have mentioned the rpm of engine being at 2500rpm in a couple of replies. Due to the load of the fan running at 100% will the fan not kick on unless the engine is at least at 2500rpm so it doesn't kill the engine or is that scenario just for testing the output?

 

Sorry for my spelling or missed words. It's late...or early. :-P

 

When you changed the fluid did you use oem fluid?

 

The fan will kick on at any RPM, the 2500 RPM was mentioned so you could compare the engine RPM to the fan RPM at a known value, that is to say it is known that a properly operating clutch fan commanded to 100% will exceed 2800 RPM's with the engine at 2500 RPM.

 

Hammer, if you have a droid phone or tablet, you can get some real capability to read your sensors (gates) for $20 to $25. The app is called Torque Pro. The app cost $5. You can download the free version if it (Torque) and get a feel for it. You will need to get a blue tooth OBDII reader to plug into the obd2 port of the truck. You can get those off eBay for about $20. Buy from a USA based seller. There have been done reports of the minis having problems. So for $25 you can have gage reading capability. It's not AE and can't commend the computer, but it's pretty good. Apple has something similar called dashboss but I think it cost more.

I decided fir $25 I would try it and buy a more extensive package when I needed it. We spend more than that on junk. I don't think I will ever need anything more extensive. It's pretty sweet. You can set it up to monitor about 30 gages on one screen. It's the best $25 I've spent in quite some time.

You can block off part of your radiator with some cardboard to get the fan to kick on more often. Don't block off the trans fluid cooler or any other cooler exept the radiator. I'd do that then take my phone out and do some test runs trying to reproduce the issue while watching the gages.