A4LD odd over drive issue

[corvairking2017]

I’ve got a 1988 ranger 2.9 with the A4LD 2 wheel drive. I got my truck back from a Trans rebuild a few months back and keep battling an odd overdrive issue that’s got me and the trans shop puzzled. I’ll be going down the highway and the truck will not lock up the torque converter or shift to overdrive. Sometimes it’ll shit as normal. Then sometimes it’ll lock up and go to overdrive and then come right back into 3rd at about 3,000 rpm’s. Then after driving a while it’ll go back to overdrive. This is my most common issue. Most of the time I can take it and put it in manual 3rd then back to overdrive and it’ll go back in overdrive. We’ve since changed the throttle position sensor and that fixed it for a few days then the problem came back. Then we changed the speed sensor and it worked for a few more days and now the issue is back. Neither of us can understand why this issue comes and goes and appears to be fixed for a few days and then return. Does anyone have any ideas as to what it could be?

 

[ford4wd08]

Have you checked the solenoids for OD and TCC lockup?

I would think that you could ground them with a manual switch while driving to just test them and see what you get.

 

[corvairking2017]

Have you checked the solenoids for OD and TCC lockup?

I would think that you could ground them with a manual switch while driving to just test them and see what you get.

i have not. I’d need to drop the babe body wouldn’t I? Wouldn’t it be odd that they both go bad together?

 

[ford4wd08]

i have not. I’d need to drop the babe body wouldn’t I? Wouldn’t it be odd that they both go bad together?

They share a common hot wire. ECM triggers the ground for each. You can test them through the plug on the transmission pan. Should have 3 wires since your A4LD is an 88.

Could be as simple as a corroded plug on the trans pan too.

If you need to replace them, you do have to drop the valve body. Not a terrible job, but it is a little intimidating.

They made a updated solenoid that has 2 holes in it later on when the explorer was out. If you were to replace them I would look for the NOS on ebay. Can save some money for Ford solenoids that have two holes.

Also if you do drop the valve body, put the transgo kit in. Well worth the 25 bucks and their tech support is second to none.

 

[RonD]

TCC and OD solenoids share a 12volt key on wire
Then each solenoid has a Ground wire back to Computer
The computer grounds that wire to activate that solenoid

If you look at the connector on the transmission it will have a 3 wire plug in
Center one is the 12volt wire

If its only 2 wires then you only have a TCC solenoid, 1988 can have either, 1 or 2 solenoids

You can use an OHM meter to test if solenoids and the wires inside the transmission are bad or good

And test if the center wire from the truck has 12volts with key on, its shared 12volts so there would be many issue, including a No Start if this 12volts was cut at the source, so would have to be a local 12volt wire issue
So move the wire around while testing, could have a melted spot or ?? after 34 years

Only other issue would be the computer itself, open it up and have a look inside, its out of warranty, lol