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When the overdrive light is flashing the transmission shifts hard

Tiny
DOCHOLIDAY10367
  • MEMBER
  • 1990 FORD F-450
  • 7.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 73,128 MILES
The light started flashing on the overdrive switch.
When it's on it shifts very hard into the next gears.
changed fluid and filter with no improvement.
I just bought the truck one month ago.
This is a non-turbo engine.
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Wednesday, July 6th, 2022 AT 11:34 AM

16 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

The idea that the light is on could indicate a few things. When it's on, will the vehicle shift to OD? Are there any conditions that seem to prompt this issue?

What I need you to do is check for diagnostic trouble codes. I remember years ago a problem with what is called a variable force solenoid failing and causing this to happen, but I need to know if there are codes,

This has an OBD1 system that doesn't require the use of a scanner to retrieve codes. Follow the directions in this link and let me know what you find:

https://www.2carpros.com/articles/ford-lincoln-mercury-obd1-1995-and-earlier-diagnostic-trouble-code-definition-and-retrieval

Also, let me know how the vehicle responds when the light starts flashing and if this only happens under certain conditions.

Take care,

Joe

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Wednesday, July 6th, 2022 AT 9:19 PM
Tiny
DOCHOLIDAY10367
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Codes 2/3. 1/3. 4/2. 4/3. 6/3.
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Thursday, July 7th, 2022 AT 5:11 AM
Tiny
DOCHOLIDAY10367
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Joe,

It comes on at startup I don't think the codes I got are diesel and transmission related. Looking at the codes I received.
Before it came on it was slamming into each gear it did go into overdrive also
i did get a new neutral shifting mlp/tr harness 1989 through 1994.
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Thursday, July 7th, 2022 AT 7:43 AM
Tiny
DOCHOLIDAY10367
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Putting it on with new plug end going to clear codes and see if it does come right back on.
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Thursday, July 7th, 2022 AT 9:50 AM
Tiny
DOCHOLIDAY10367
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Went 3.8 miles did fine, shut it off waited a few minutes started it. An od light went back to flashing and changing gears went back to banging into every shift of transmission.
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Thursday, July 7th, 2022 AT 10:37 AM
Tiny
JACOBANDNICKOLAS
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Hi,

The codes aren't all listed for this vehicle. The ones that seem related to the fuel system and not the transmission.

I feel there is an issue with one of the pressure solenoids in the transmission. Have you checked line pressure?

Let me know.
Joe
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Thursday, July 7th, 2022 AT 1:35 PM
Tiny
DOCHOLIDAY10367
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Joe, no, I'll have to get a line pressure set at parts store and would you know where the hookup would be?
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Thursday, July 7th, 2022 AT 2:02 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Here is the tricky part. If the light wasn't flashing, things would likely show normal. So, it would need to be done when it's flashing.

Also, has anyone added a transmission cooler? I've seen them be partially plugged causing lower pressure.

By chance, do you know what model the transmission is? If you have that, I should be able to find the specs and directions for checking the pressure.

Let me know. Also, you may want to flush the cooler if there is one on it. It's just a theory, but it is a possibility.

Take care,

Joe
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Thursday, July 7th, 2022 AT 4:51 PM
Tiny
DOCHOLIDAY10367
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Joe,

It doesn't have an external cooler. So, I flushed lines both ways with clean fluid through radiator no change cleared codes again let it sit all night batteries disconnected. This morning it started let it warm up, no flashing light, drove it six miles out and six back home light was still off. I will drive it in the morning to the parts house pick up solenoid pack for transmission I will keep it incase light stays off if it comes back on ill replace the solenoid pack and try again and also pick up a line pressure set, and it is an e40d transmission.
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Friday, July 8th, 2022 AT 3:10 PM
Tiny
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Hi,

That's actually encouraging. Let me know if it comes back on. Hopefully, it won't, but if your like is like mine, well, it likely will.

Take care and stay in touch.

Joe
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Friday, July 8th, 2022 AT 8:13 PM
Tiny
DOCHOLIDAY10367
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Joe,

So far 86 miles, still okay. I'll see if I can get 160 more fixing to go to Williamsburg and that's 86 miles away an then back cross my fingers, lol.
Thanks for your help, Bob.
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Wednesday, July 13th, 2022 AT 6:58 PM
Tiny
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Hi,

Thanks for the update. That's good news. I have a question. Williamsburg PA or VA?

Take care and let me know if the trip is a success.

Joe
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Wednesday, July 13th, 2022 AT 10:16 PM
Tiny
DOCHOLIDAY10367
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Joe,

It's Williamsburg KY, lol.
Thank you again for all the help.
Have a great day. Bob
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Thursday, July 14th, 2022 AT 3:48 AM
Tiny
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Hi,

I'm not far from Williamsburg PA. LOL

Take care,

Joe
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Thursday, July 14th, 2022 AT 7:06 PM
Tiny
DOCHOLIDAY10367
  • MEMBER
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Hey Joe, well, the flashing light came back on several times, and I did some voltage probing on sensor above the timing cover in front of injection pump which was sporadic and leaking oil out of the 2 wires I also cleaned all the battery cable connections and replaced the throttle position sensor which was listed to cause shift problems.
So far, I've put 180 miles on it and no problem.S
Thanks, Robert
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Tuesday, August 9th, 2022 AT 6:42 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Thank you for the update and you are very welcome. I'm glad to hear it's working for you.

If anything changes, let me know. Also, please feel free to come back anytime in the future if you have questions.

Take good care of yourself.

Joe
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Tuesday, August 9th, 2022 AT 8:25 PM

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