There is a slight slip in the transmission?

Tiny
SWEETIE1965
  • MEMBER
  • 2001 FORD F-150
  • 5.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 211,000 MILES
I just purchased the truck listed above. It has a slight slip in the transmission when you first take off in drive and reverse. Once it's going everything is fine. When I stop at a red light or something like that, it slips slightly again until it gets going again. I scanned for codes zero the only code it gives me is a misfire in #8 cylinder. What do you think is causing the slight slipping? I still have yet to change the filter and fluid I need the transmission. I don't want to do anything yet in case I need to drop the pan again for something else.
Sunday, December 11th, 2022 AT 7:26 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

If this is the original transmission, the clutch plates could be worn. Does it slip in reverse? I ask because the low/reverse clutch pack is the same one.

On the other hand, there could be several other causes. The most common would be an issue with transmission line pressure due to a failing pressure solenoid, a partially plugged transmission filter, or even a partially plugged transmission cooler.

The only this that is going to make this difficult is not having codes. When you checked the fluid level and condition, was it clean and full? Is it a brownish color and is it full when the engine is at operating temperature, running, and in park?

Let me know.

Joe
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Sunday, December 11th, 2022 AT 8:47 PM
Tiny
SWEETIE1965
  • MEMBER
  • 177 POSTS
I checked the transmission fluid while the engine was cold, it read full. Then I checked it when the engine was at operating temperature. It didn't read anything on the dip stick. While the engine was running, I went through all the gears slowly to make sure the fluid was getting where it should be. It read nothing on the dip stick when the engine was warm but when the was cold it read full. It's of natural color and does not look or smell burnt. I will add some fluid to see what it does then.
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Monday, December 12th, 2022 AT 10:58 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

That is the opposite of what I would have expected. Transmission fluid expands when it gets hot. That is why it needs to be checked when it is warm. When it's cold, it should read low or in a "cold" range.

If the fluid is both clean and full, and the transmission shifts properly but slips in first gear (D) and reverse, I suspect it deals with worn clutch plates in the low/reverse clutch pack. The only way to confirm that would be to take it apart. However, before I would go to that extreme, I would likely check line pressure.

Let me know your thoughts. Also, confirm the fluid level. It should be low when cold and go up as it warms up.

Take care,

Joe
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Monday, December 12th, 2022 AT 8:16 PM
Tiny
SWEETIE1965
  • MEMBER
  • 177 POSTS
It reads full while the engine is cold. Once the engine is warmed up at operating temperature, nothing reads on the dip stick. I will put some fluid in it tomorrow (Thursday) to see what it does (weather permits, the weather is supposed to get pretty bad here for the next couple days.) I will let you know what it does after I add fluid.
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Monday, December 12th, 2022 AT 8:32 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Okay, I know what is happening. The front pump in the transmission is likely worn. What happens is this. The torque converter holds a few quarts of transmission fluid. The torque converter connects to the front of the transmission's front pump.

Under normal conditions, the front pump seals off the converter from draining. If it is worn and allows the torque converter to drain off, the fluid is going up after sitting, and then when it is warm and running, the converter is refilled and the fluid is low.

In this case, you should fill it when the engine is warm and running. However, after it sits overnight, the fluid level is going to show over full.

What does all of this mean? The front pump and converter likely need replaced. However, once the front pump is removed, then you have access to the clutch packs in the transmission and should inspect at a minimum the low/reverse clutch pack for wear.

Let me know if this makes sense. Also, let me know if you have other questions.

Take care,

Joe

See pic below. I circled the torque converter and highlighted where the front pump is located.
Image (Click to make bigger)
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Monday, December 12th, 2022 AT 8:52 PM
Tiny
SWEETIE1965
  • MEMBER
  • 177 POSTS
I am thinking about buying a 2002 Ford Ranger with a 3.0-liter engine automatic transmission. The owner of this truck says someone told him the oil pump shaft broke so there is no oil pressure. How do I distinguish the problem being either the oil pump itself or the oil pressure switch/ sensor? I don't have a manual gauge to see what the actual pressure is. I know the engine would make all kinds of noise if the oil were not getting to the proper places.
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Friday, December 16th, 2022 AT 10:54 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

I have a favor to ask. We try to keep the threads specific to one topic and one type of vehicle to make it more helpful to others. So, is it possible for you to copy and paste your new question to a new thread?

Here is the link to start a new thread:

https://www.2carpros.com/questions/new

I hope you understand. Just copy and paste your new question and someone will help. Note: Make sure to include the engine size and mileage on the vehicle.

Take care,

Joe
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Friday, December 16th, 2022 AT 9:20 PM

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