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Does not shift into 4th gear


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Recently, I had a coolant line blow out which lead to coolant all over the engie compartment. I replaced the hose and filled back up with coolant. It ran fine for almost a whole day. I jump started someone, parked it for 20 minutes, and when I went to drive it again the truck would not shift into fourth. I can shift into 1st 2second third, and reverse. I checked the 3 solenoid ohm readings and they are 21. What else? Desperate need of help...

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Okay I take back what I said. On the trans connector side I probed e,f, and g to b which is ground. All connections were open. Then I probed e,f, and g to the engine and got the following..

 

E 15.2 ohms

F 18.e ohms

G 15.7 ohms

 

When I probed b on the trans side to engine ground I got nothing. Then I probed b on the tcu side and got .2 ohms.

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Sounds like you popped a fuse in the jump.

 

Check the 10A TCU fuse under the dash, passenger side.  It's in-line in the wiring harness for the TCU.

 

Check the "TRANS" 7.5A in the fuse panel by your left knee.

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Okay I take back what I said. On the trans connector side I probed e,f, and g to b which is ground. All connections were open. Then I probed e,f, and g to the engine and got the following..

 

E 15.2 ohms

F 18.e ohms

G 15.7 ohms

 

When I probed b on the trans side to engine ground I got nothing. Then I probed b on the tcu side and got .2 ohms.

 

Where are you taking your ohm readings? From the disconnected wiring connector on the firewall from the TCU to the tranny?

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Yes the white connector. Ive looked at other posts and seen diagrams of where each wire goes.

 

The pinouts may be different. On the tranny side of the connector, check and see which pin is actually ground. See if it is in fact pin B. Pins E, F, and G to ground all read ~15 ohms. But your 89 may not be the same.

 

Do you have the AW4 manual? I can send it to you if you PM an email address.

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The AW4 manual says 11-15 ohms; replace if reading is above or below the specified range. Mine all read on the high side (~15) within .5 ohm of each other. Looks like if S2 was not closing you would have no 2nd or 3rd gear. You could try applying 12V to pin F while monitoring the contacts with an ohmmeter to see if it's making.

 

Do you have a spare TCU?

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I know the 91 TCU pinouts are different than the 90 and below, so I doubt a 98 TCU would work.

 

And yes; when you apply 12V to the solenoid coil (pin F for solenoid #2) the solenoid will close and you will go from an open to continuity on the ohmmeter. You will probably be able to hear it click also. If it's working that is. You can verify it on another solenoid. You can use a 9V battery for testing relays and solenoids.

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So a nearby junkyard has a 1988 wagoneer. Ill see if that tcu works.

 

Since the tcu connector is disconnected and I'm able to shift manually, is that why I do not have OD or a WOT condition? It seems to skip 2nd as well.

Yes, and yes.

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Reverse: goes into reverse

Park: no movement

Neutral: no movement

 

1-2: first gear only

Can then shift to 3rd...

3: 3rd gear

Can then shift to D

D: shifts into gear but doesnt seem like much of a change. I think because the TC isnt locking up.

 

Can downshift from D to 3 to 1-2

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