1990 Toyota 4Runner Won't Shift back to 2WD

MNEATHERY59

MEMBER
1990 TOYOTA 4RUNNER
6 CYL
4WD
AUTOMATIC
246,000 MILES

My Toyota has a rebuilt transmission and was driving fine in 2WD. Then it was put into 4WD and would not shift back again. The transmission fluid is full, and the vehicle acts like it wants to shift, but does nothing while in 2WD. The 2WD seems to work fine until it is changed to 4WD and then it will not go back. Any suggestions on what the problem might be?

5 Replies

KHLOW2008

MECHANIC
41,814 POSTS

Hi mneathery59,

Thank you for the donation.

Problem can be due to a faulty transfer position switch or # 4 solenoid.

Does the OD light blinks while driving?

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Wednesday, September 29th, 2010 AT 12:23 PM

MNEATHERY59

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3 POSTS

Thanks for the reply. The OD light does not blink while driving. Does this help pinpoint the problem?

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Thursday, September 30th, 2010 AT 1:36 AM

KHLOW2008

MECHANIC
41,814 POSTS

Without the OD light blinking, it is more difficult to diagnose the problem as the fault is not noticed by the Transmission Control Unit.

Possible causes are :
1. Manual linkage faulty or out of adjustment.
2. Faulty Electronic Control,
3. Faulty Valve body
4. Faulty transfer case.

Does the 2WD operate when engine is turned off and restarted? If not, does it start working after vehicle is park for extended periods?

If answer is yes to above, check Solenoid # 4, it could be stuck after being activated.

Note if the problem occurs when shifted to H4 or it only occurs if it is shifted to L4.

There are 2 types of transmission used, A340 F, ( mechanically control 4WD transfer) and A340H, ( electronically controlled 4WD transfer). I believe yours is the A340-H.

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Thursday, September 30th, 2010 AT 1:28 PM

MNEATHERY59

MEMBER
3 POSTS

After re-checking the vehicle here is what I discovered"

1. The OD light blinks when vehicle is in 2wd and not working. The light goes out when it is in either 4H or 4L, which seems to be working.

2. 2wd does work occasionally, but it slips badly. Sometimes is will go while in this gear with a lot of gas and sometimes it will not. It does not slip noticeably while in 4wd.

And a general question, what does the shift override button do?

One of your suggestions was to look at the #4 solenoid. Is there a way to test the solenoid?

Thank You

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Saturday, October 2nd, 2010 AT 6:43 PM

KHLOW2008

MECHANIC
41,814 POSTS

The OD switch is for turning the OD gears on or off and also acts as an indicator light for control faults in the system.

Snce the OD light was blinking, it indicates an error has been detected and trouble codes would be stored in the control unit.

Retrieve the trouble codes and see what you come up with.

DIAGNOSTIC CODES
CAUTION:Ensure battery is fully charged prior to testing. Low battery voltage will cause faulty diagnostic system operation.

Reading Diagnostic Codes (W/O Super Monitor Display)

1. Turn ignition on with engine off. Ensure overdrive switch is in the ON position. Diagnostic codes can only be read if overdrive switch is in the ON position.

2. Using a jumper wire, connect terminals as shown.

3. Diagnostic codes are read by counting the number of times the "OD OFF" light flashes on the instrument panel.

4. If transmission electrical system is operating normally the light will blink 2 times per second.

5. If there is a malfunction in the system, the light will blink. The number of blinks will equal the first number of the diagnostic code. After a 1.5 second pause, the second number of the diagnostic code will flash. If there are 2 or more codes, there is a 2.5 second pause between codes.

6. Remove jumper wire. If codes are stored, note code number and repair appropriate circuit.

NOTE:
If several diagnostic cores are stored, the lowest number code will flash first. Other codes will flash from lowest to highest number.

7. If diagnostic codes 62, 63, 64, 65, 73 or 74 occur an electrical failure in the solenoid is indicated. Mechanical failures such as sticking switches will not appear as diagnostic codes.