After rebuilding transmission there is an odd fault

Tiny
BRIAN WOOD
  • MEMBER
  • 1994 MITSUBISHI GALANT
  • 1.9L
  • 6 CYL
  • 2WD
  • 130,000 MILES
I have the car listed above with a recently fully rebuilt Auto transmission at 125,000. It now drops and locks into either 2nd or 3rd at random at speed, so will drop from third to second or 4th to third and no one seems to know what's causing it. May have caused original failure at 125,000. Any thoughts or suggestions are welcome. It appears maybe electrically based. Restarting the car will sometimes fix it for a short time.
Saturday, December 25th, 2021 AT 1:27 PM

8 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

What fault code was retrieved? The idea that it is downshifting could be related to a speed sensor or even a kick-down servo switch at the front of the transaxle. I say that because it is downshifting on you at odd times.

Let me know as much as you can. Also, let me know if you have a live data scan tool, the fault code found, and I need the correct engine size. According to my manual, it came with a 2.4L SOHC or a 2.4L DOHC. See pic below.

I will watch for your reply.

Take care,

Joe

See pic below.
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Saturday, December 25th, 2021 AT 10:35 PM
Tiny
BRIAN WOOD
  • MEMBER
  • 5 POSTS
Hi Joe, the mechanic never mentioned scan codes to me.
The Auto failed at 125,000 was rebuilt completely and ran perfectly for approximately 2 months. Locked into second gear went back with a server/solenoid change and was good for another 6 weeks then locked into third. Server/solenoid changed again on third gear and lasted for approximately 1 month.
Fault found was electrical issue and came back working perfectly. Lasted 6 weeks then locked into third again. In at moment. Around 2,000 done between all issues. It's a pain but a classic so the mechanic has been great but losing hair at a rapid rate.
Appreciate your input, so thank you. We serviced the transmission pre failure at approximately 115,000 on buying it. This is the one we have.
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Sunday, December 26th, 2021 AT 2:02 AM
Tiny
BRIAN WOOD
  • MEMBER
  • 5 POSTS
On further thoughts I did mention scan codes to him and said there were none showing.
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Sunday, December 26th, 2021 AT 3:53 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Brian,

If it is going into limp mode (stuck in a specific gear), there really should be codes that are related.

If you presently have the car at home, try to retrieve codes yourself and let me know what you find. Because of the model year, this vehicle has an OBD1 system that doesn't require a scanner to retrieve codes. All that you need is a very basic voltmeter or multimeter that can check continuity.

Take a look through this link that explains in detail how it's done. Let me know if you are comfortable doing this.

https://www.2carpros.com/articles/mitsubishi-trouble-code-definitions-and-retrieval-procedure-for-odb1-system

Also, I attached a copy of the wiring schematic for the transmission. I highlighted the wires that are related to the transaxle solenoid valves. Note where they all go to. Each one is controlled by the transaxle control module located under the dash in the vehicle.

The chances of two solenoids failing this quickly are low. I suspect there is either a wiring issue between the solenoids and the control module that is being temporarily fixed when work is done. After a short time, the connection is lost.

Of course, that is a theory at this point. However, before I would replace more parts, I would wiggle wires, disconnect and reconnect harnesses and inspect them, and see if it makes things work again for a period of time.
I
Let me know. If that has been done, then it's time to start checking wiring for faults. If one exists, it is likely in the transmission. The solenoid valves are attached to the valve body. See pic 3 below.

Let me know if you are able to get codes or if there is anything I can do to help. Also, let me know if the valve body was replaced during the overhaul.

Take care,

Joe

See pics below: Note: I had to cut the wiring schematic in half to make it readable. However, I did overlap the two pics and highlight the wiring involved.
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Sunday, December 26th, 2021 AT 8:12 PM
Tiny
BRIAN WOOD
  • MEMBER
  • 5 POSTS
Great info. I will pass all this information on when I see the mechanic this week. They want it fixed as much as I do as this car is worth saving in my mind. It does seem electrically based at this stage, it's just what and where. Their opinion is it took out the transmission at 125,000 so they don't want to destroy the rebuilt one as well. The joys of old cars. Whatever the outcome i'll let you know so others with these transmissions can hopefully stop it before further damage occurs.
Cheers, Brian.
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Monday, December 27th, 2021 AT 8:08 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

That sounds like a plan. With the cost of used vehicles being up 46%, we need to keep the older ones going. This is certainly one worth saving.

I look forward to hearing what is found. However, if I don't hear from you for several days, I hope you have a great New Year!

Take care of yourself.

Joe
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Monday, December 27th, 2021 AT 8:15 PM
Tiny
BRIAN WOOD
  • MEMBER
  • 5 POSTS
Well, after 2 full auto transmission rebuilds and then a 3rd failure of locking into 3rd gear the fault was finally found. It was a rubber seal within one of the 3 gearbox soloniods that was the culprit. Took a while to find it but apparently was a known issue in the 94/5 auto transmissions for failure. All 3 were replaced and 6 mths later, and on, no further issues. 2yrs and 9 mths of dionostics was the end result.
The car is to good to ever give up on.

Cheers and thank you for helping out with your very informative information.
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Thursday, May 9th, 2024 AT 12:56 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

Thanks for the update. Wow, it has been a while. Regardless, I'm glad you have been able to resolve the issue.

Take care and feel free to come back anytime in the future.

Joe
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Thursday, May 9th, 2024 AT 7:40 PM

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