No overdrive

[rodb]

Decided to remove the valve body, took out the 25 bolts but will not come down, is there something else I'm missing? Does the reverse servo 4 bolts also have to come out?

 

[rodb]

Update: Removed the 4 bolts holding servo and it did come out, how do I get all the old fluid out without turning upside down ?

 

[rodb]

Bench tested both solenoids, they are opening and closing when voltage is applied. Looks like problem is somewhere else, any more ideas ?

 

[rodb]

Looks like I'm at standstill, have done everything that was suggested, I was hoping to get further direction.

 

[MrShorty]

If the solenoid is working, then the fault must be mechanical or hydraulic.

It seems that one of the common 4th gear failures that I see mentioned is the 4th gear planetary dies somehow. From http://etereman.com/blog/ford-trans...ssion-that-all-shop-owners-should-be-aware-of

I would also keep an eye out for problems with the overdrive planetary gear. They were pretty fragile and broke often, and were eventually updated to a six pinion gear planetary.

How far can you, personally, go into the transmission diagnosing and repairing? I have never been deeper than the valve body. If the valve body looks clean and the solenoids and valves are working, then I'm not sure I can help any further than that.

 

[rodb]

Thank you for all your help. My only last thought relates to the first paragraph in my post #36 , can someone please respond to the ohms reading I got on that plug.

 

[rodb]

Is it possible the overdrive band could be out of adjustment ? Think it is currently at 1 1/2 turns out.

 

[FR-425]

Thank you for all your help. My only last thought relates to the first paragraph in my post #36 , can someone please respond to the ohms reading I got on that plug.

Sorry gone for a few.

I would attribute that to measuring through the harness and connections.

If the thing was failed you would get open circuit, that's really all were looking for.

So what next? "THE SCREEN" The screen is a bad idea installed in the 3-4 bore it can be removed and cleaned or removed all together.

Either way you are pulling and rebuilding the valve body or just that bore.

Blue arrow is "the screen" Ignore the red arrow

Here's the shift chart for the A4LD.

It is important to note that the TCC can engage when in manual 3rd gear. Skipping 4th altogether. So a test drive in manual 3rd will help trouble shoot TCC operation. (Easy for people to assume they have no 4th gear when in fact they have no TCC lock up.)

Note that the overdrive band is only engaged when in 4th gear. You can visually inspect the OD band from underneath with the valve body off.
See pics and info here: http://www.explorerforum.com/forums/showthread.php?t=158160

 

[rodb]

Yes mine did not have that screen, assume when it was rebuilt several years ago it was removed. Not sure if my trans has the single or double wrap overdrive band, I checked it and was set at 1 3/4 turns out, tried 1 1/2 no different, then set it at 2 turns out and left it there. When I test drove the tac does drop a few hundred rpm at around 50mph and feels like its going into overdrive but when cruising down freeway at 65 in overdrive the tac is at 3,000 rpm and when dropping down to 3rd the tac stays at the same 3,000. This doesn't make sense. By the way I have the 3.73 gears. Thanks again for your help.

 

[gmbroy]

rodB Now let me ask you this when you put your shift selector into d 2 or 1 if you go down a hill does the transmission stay engaged or does it let it drift ? Say if you are in cruse control at 55 & you go down a hill the trans will let the explorer drift to save on gas if its in OD . when you have it in drive , 2 or 1 the engine should be holding it back . if it drifts in all gears then you have a overdrive clutch problem or the OD one way clutch is damaged . mine has been doing this for 50,000 miles . I just drive on hi ways at 55 . just see if you have engine braking in drive , 2 & 1 , if you don't i think its tranny pulling time or run her till she stops . let me know if this helps any !!!

 

[rodb]

I have no engine braking in 1st or 2nd when going downhill.

 

[gmbroy]

OK mine is doing the same thing as yours no overdrive , no engine braking in drive , 2 or 1 . the problem is with the overdrive clutch , the overdrive one way clutch or both . that requires pulling the trans & pretty much gutting it . at that point I would go with a reman or a rebuild . But mine has been running like that for 50,000 miles so it might last you awhile . as you have no engine braking your brakes will wear out faster . so at least now you know your problem . there is no easy fix to this problem & for that I am sorry for you . But the explorer is worth fixing . its the last truly vehicle you can shade tree mechanic on . wish you luck & feel free to contact me at any time you need . we here are dedicated to helping each other all we can .

 

[natenkiki2004]

Have a look at the ATSG:
https://dl.dropboxusercontent.com/u/464376/vehicles/1991 Explorer/a4ld_manual_atsg.pdf

Book page 23, PDF page 21. It talks about no engine braking in 2nd gear. As gmbroy said, it's probably the Overdrive one-way clutch.

It does talk about bands though but you already tried adjustments. It mentions the intermediate servo leaking, that's an easy replacement without dropping the trans. Might be worth investigating if the issue really bothers you. From what I've heard, the clutches in these transmissions are pretty good unless the fluid was never changed or it was launched from a stop a lot. It's usually the other parts that break. I remember the previous owner of my rig had the trans rebuilt with probably at least 150k on the clock. He said you could still read the part numbers off of the clutches. Though, we're talking about the OD clutch, maybe your Explorer saw a lot of towing in OD?

 

[rodb]

This truck has been in family since new, has not towed. The trans was rebuilt at 105,000 in 2005, currently has 160,000. I keep thinking it is something simple, I have not checked the intermediate servo or speed sensor yet. Its been a really good truck, I can remember when my dad bought it brand new, its been passed down to several family members over the years, I've had it almost 4 years now.

 

[natenkiki2004]

It would have to see a LOT of abuse in 55,000 miles to burn up the clutches. But maybe there was a defect and one cracked or something, hard to say. Check all the bolt-on stuff you can, you might just get lucky.

 

[rodb]

This truck has not been abused or driven hard, thats why I think it is something simple, not sure how to check the overdrive servo, could it be that simple ? The fluid looked clean when drained.

 

[natenkiki2004]

I agree, if not abused, it should be something simple. I believe the servos are the big cylinders on the driver's side. I think they can be removed either from underneath or from the access panel. I haven't done it myself but it's worth taking a look at.

 

[rodb]

Can the throttle kick down cable cause no overdrive? I noticed the cable does not pull even with gas pedal to floor. Pushed the button on firewall and pulled on cable but still doesn't seem to pull with gas pedal to floor.

 

[natenkiki2004]

It might if it was pulled constantly all the time. If it's slack all the time, you just won't get kickdown when trying to pass someone or climb a hill.

Thinking in terms of that direction, I wonder if the vacuum diaphragm could cause issue here. It will hold or delay shifts depending on how much you're into the throttle. Light throttle (high vacuum) means shift earlier.

 

[rodb]

Pulled the cable on inside of cab, drove and the kickdown is working. Truck shifts fine 1-3 no delays and not too soon. The more I research, there are so many potential things that can cause my issue, I'm not one to give up but seems like I've tried everything.