I have my first automatic transmission and am a little confused about how it shifts sometimes. It is a 01 F-350 CC 4X4 V-10. I watch the rpms to see what the transmission is doing. It shifts from 1st to 2nd to 3rd ok and then the rpms drop down to what I would call 3rd and 1/2 before finally dropping into overdrive. It seems to have an extra shift also sometimes when it shifts down. Again it would be between od and 3rd. Do I understand right that this should have 1st, 2nd, 3rd and OD like a manual would, or do automatics sometimes find in between places to go to???

 

What is happening is when the trany shifts to OD your torque converter clutch disengages and causes the converter to slip and then soon after the shift it locks back up giving you the 3rd and a half feel. This is completely normal.

 

I have been paying close attention to the way my truck shifts since my original post and am still not sure I understand how it is working. The 3rd and 1/2 I feel is right before it goes into od and makes my truck seem like it has a 5 speed automatic. Sometimes if speed is maintained constant, it stays in this extra "gear" for 30 seconds to a couple of minutes. It feels like it would stay there indefinitly, but normal driving usually entails an eventual adjustment of acceleration and this moves it out. I can kick it back up to 3rd or drop it into od sooner by increasing or letting off the accelerator, but this is not always possible or desirable in traffic. In situations like entering a freeway, it passes through this gear rather quickly, but at speeds of 40 to 45 mph it can stay in it much longer. Is this really normal shifting? Could someone explain in simple terms what the torque converter does and why. Also why it only seems to come into play between 3rd and od? Also if there is any harm in letting it stay in this extra gear for longer times as it sometimes wants to.

 

The torque converter replaces the clutch in an auto trannie. It is basically one glorified fan blowing fluid on another glorified fan to make the second fan and thus your truck move. The first fan is attached to your flywheel, and the second is the input to your trannie. There is no mechanical connection between your engine and transmission, just a fluidic one. The problem with this is that it can be very inefficient, as the best torque converters run only about 95% efficiency when cruising, and anywhere from 40-60% when under acceleration. To combat this, the lock-up converter was developed. This has a clutch in the torque converter that actually locks up in 3rd and 4th gears, to give 100% transfer of power from the engine to the trannie. This is in no way bad for your truck, and is actually helpful to your fuel economy.

The Law

 

Thanks for the explanation. I really know very little about how an automatic works, having had only manuals for my first 30 years of driving.

The main question I still have is this: I now understand that this 3rd and 1/2 is normal, but is it normal and ok for my transmission to spend SO MUCH time (see earlier post)in this in between "gear" where (if I am understanding your explanation correctly), the torque converter is doing it's thing?

Also, if it locks in both 3rd and 4th gears, why is the extra gear apparent between 3rd and od? Does it lock in 3rd, unlock to go into od, then lock again in od? Is the 3rd and 1/2 I notice just the time it is unlocked between 3rd and od? If so, why does the truck still have power from the transmission when it's unlocked? I apologize if I am not totally "getting it" yet, but I suppose that (miracle of miracles), maybe I am starting to understand a little.

Thanks to all who are educating me on this.

 

[updated:LAST EDITED ON 28-Jan-02 AT 01:34 PM (EST)]The transmission will shift 1-2, 2-3, and then the torque converter will lock. If you don't go fast enough for it to shift 3-4 it will stay in 3rd gear with the torque converter locked indefinitely. That's normal, and won't hurt a thing. If you do go fast enough to shift 3-4 the torque converter will slip some during the shift, but it does not unlock and then relock.

The transmission will also transmit torque unlocked, it just isn't as efficient.

There is always power tranmsmitted through the transmission. In fact, with the torque converter locked there is more power transmitted because locking the torque converter eliminates most of the inefficiency of an automatic transmission.

Mark

 

>The transmission will shift 1-2, 2-3, and then the torque
>converter will lock. If you don't go fast enough for it to
>shift 3-4 it will stay in 3rd gear with the torque converter
>locked indefinitely.

I understand the above perfectly, but I may not be making it clear what my question is.... What happens on my truck is that between 3rd and 4th or od, there is another "gear" that my truck stays in for anywhere from a few seconds to a minute or two depending on speed and acceleration. I am asking about this "3rd and 1/2" gear and the time my transmission spends in it before dropping into od. It is a very noticeable position between 3rd and od. Not much different than the shift between 1st and 2nd or 2nd and 3rd. When I first got the truck, I thought I had a five speed transmission. That's the way it shifts all the time, every time.

Thanks

 

Between 3 and 4 the extra gear you are feeling is the torque converter slipping a little bit. When you accelerate the torque converter locks up and the tranny goes to 4. Benjamin

 

Letting it stay like this for an extended time (over 30 seconds) will heat up the transmission fluid and could cause damage. Benjamin

 

Now a question. I had no idea that there was no mechanical link between the engine and tranny. How does the fluid move that much weight? Thanks. Benjamin

 

[updated:LAST EDITED ON 28-Jan-02 AT 09:03 PM (EST)]I was following your questions and wondered if you had your question resolved? I just had the same question a few weeks ago. If you don't mind I thought I'd explain it as I understand it.

The TC transmits power via the use of fluid. Because of this the engine spins a little faster than needed than if you were to have it drive the transmission directly. (ala your manual.) You see it's gotta run a pump that pumps the fluid. That third and a half "gear" is not a gear but the TC locking up. When it locks up, (it's just like a clutch) engine speed and transmission speed will then "match". 100% mechanical energy, no wasted energy (RPM) to move fluid. Hence the drop in RPM. If it stays there for awhile, it's ok, it's locked.

I don't know about the slipping thing. Lock out your OD (via button on stalk) You'll feel it lock-up without it going into OD.

I was obsessed with this for days. Mark really helped me to understand it. I just hope I'm not understanding it wrong. So, if I am someone please correct me. I was just beginning to think that autos weren't really PFM and maybe just FM.

 

Thanks Monsta. Thanks to everyone, I think I finally basically understand how this transmission works, but I'm not 100% convinced I have an answer to my original question. Benjamin said that if you "let" it stay in between 3rd and 4th for more than about 30 seconds, it will heat up the transmission. Problem is that I don't really "let" my transmission do this. I just drive the truck and usually it passes through this 3rd and 1/2 gear quickly. (a few seconds) Sometimes, especially around 40mph, it will stay here for an extended period of time. Usually until traffic or road allows me to accelerate or let off the gas. Today on the freeway, it was in this position for 30 to 40 seconds from 45mph to 60mph when it dropped into od. (btw, I am positive it is in between 3rd and 0d, I count the shifts and it was definitely not still in 3rd). On the freeway if you are in od and step on the gas a little, but not enough to kick it into passing mode, it will sometimes go into this in between gear. The rpms also fluctuate a bit in this position without any change in gas, sometimes dropping down in a few smaller steps before going into od. Sort of like 3rd and 1/2, then 3rd and 3/4, then 3rd and 7/8.??? Different than 3rd or od where it feels like it is in a definite locked in gear and rpms only change in response to the gas pedal.

So... anyway, my original question was... Is this normal, ok, or is it an indication of an issue with my transmission that may be a problem down the road? There are only 5,500 miles on the truck. Service dept. of dealer says it is the normal way all these V-10 automatics work, but dealers first answer is often that any concern is normal functioning. If I can educate myself enough on this and I feel it is an issue, then at least I can make the service dept. document it in the history off the truck. In case the transmission goes out at 36,001 miles!

 

Benjamin is wrong. You can run all day long in the "in between" gear, as you call it. It's really in 3rd gear with the torque converter locked. That is the operating condition where the transmission makes the LEAST amount of heat!

The transmission shifts 1-2, then 2-3, then the torque converter locks, eliminating the slip in the torque converter, then the transmission shifts 3-4. Each of these happen at a higher speed than the event before it. If you run at a speed too low to shift to 4th, it will stay in 3rd gear indefinately. That is how it should work, and it won't cause any damage at all.

IF you want more information on how a torque converter works, go to www.howstuffworks.com. They have a good explanation, plus one on how a transmission works.

Mark

 

Mark - I reread your post with a little more knowledge now and have 2 simple questions.
You said: "The transmission will shift 1-2, 2-3, and then the torque converter will lock. If you don't go fast enough for it to shift 3-4 it will stay in 3rd gear with the torque converter locked indefinitely. That's normal, and won't hurt a thing." IS this position, in 3rd with the torque converter locked, what I feel as 3rd and 1/2? or... You also said: "If you do go fast enough to shift 3-4 the torque converter will slip some during the shift, but it does not unlock and then relock." OR is this slipping during the shift what I feel as 3rd and 1/2?

Thanks

 

Boy Mark, you are good! . I think you slipped the answer to my question to you into the thread, before I even posted it!

Thanks