No overdrive

[rodb]

Noticed that my overdrive is not working on my '91 Eddy 4.0, on freeway it is 3000 rpm doing 65, watching tac at that speed and shifting between drive 3 and overdrive the rpm stays same. Any ideas ?

 

[arco777]

Shift solenoid fixed that issue on a '94 I had. It is replaceable without too much effort.

 

[rodb]

So I can drop the pan and replace it? Any further info would be appreciated.

 

[arco777]

Yes, you don't have to remove the trans to do it. I don't think you even need to remove the valve body.

One source for a new solenoid is TransmissionPartsUSA dot something.

 

[rodb]

I looked at my Haynes manual, absolutely no info on how to work in transmission.

 

[arco777]

Haynes manuals aren't very helpful to be honest. Search the forum for "A4LD Valve Body Rebuild Diary". Good info there. Also search the forum for overdrive solenoid replacement, that sort of thing. Tons of info on here.

There are slight differences between early (91) and later (94) valve bodies. I'm not sure, but I think earlier VBs had only one solenoid.

If you are doing infrequent work on the truck, most of the time you can find the info you need on this forum by searching. Once in a while you get a technical item that may not have been covered yet. Might want to invest in a Ford factory service manual (on CD). Has helped me a lot. Mine is for 93/94 or I'd send it your way.

 

[MrShorty]

Before replacing the shift solenoid, I would check the circuit as best I could. It would be a shame to replace the solenoid only to find out that something had come unplugged or a broken wire was the cause.
These shift solenoid circuits are fairly straightforward DC circuits. Power is provided through the EEC relay, and the PCM acts as a ground side switch. I know I have detailed the test sequence somewhere on this forum. Basically, you hook up your meter to measure voltage drop across the solenoid. Run the "output state test" (see my notes on pulling EEC-IV codes thread or other description of this test protocol) and see if you can see the PCM energizing/de-energizing the circuit. Then a road test to see if the PCM is choosing to command the 3-4 shift. If the PCM never chooses or cannot command the 3-4 shift, then you can investigate the wiring and computer controls to understand why the PCM won't command the shift. If the PCM commands the shift, but the transmission does not respond, then you can look into the transmission to figure out why the transmission does not respond.

 

[larrydd999]

Looking at some troubleshooting information from my hard copy of the ATSG manual for the A4LD, I see quite a list of possible causes for no 3-4 upshift. I don't want to type all of that but the CD version of the manual and the supplement is - or at least was - on this site. I wasn't able to find it just now, but perhaps someone else knows where it is.

 

[rodb]

Yes I have been searching this forum and see that this topic has been around for a least 10 years, I have not come across the specific steps to trouble shoot this issue. I do have a good multi meter but not sure exactly where to start testing. For now I will start with the simple stuff such as making sure the plug in connection to the trans is good, thanks to all of you for your ongoing help.

 

[arco777]

Maybe these will help. From the 1993 Ford service manual. All the electronics that need to be functioning correctly for transmission electronic controls.

Ignore the V8 style coil pack reference. There was also a reference to a conventional distributor which I removed. This info is for the A4LD but for some reason it had a couple V8 items in the troubleshooting. The TPS doesn't look right either. Perhaps someone at Ford thought the A4LD would be behind a V8 at some point.

 

[arco777]

Here's the link to the valve body rebuild diary. http://www.explorerforum.com/forums/showthread.php?t=137972

Post #10 in that thread shows the solenoids.

I don't remember if you can remove the solenoids without dropping the valve body. There may be a keeper internally which prevents it. Dropping the valve body isn't hard, you'll need a inch/lb torque wrench for re-assembly and a new set of gaskets.

Link to new set of gaskets: http://www.transmissionpartsusa.com/A4LD_transmission_valve_body_gasket_set_p/230-00023135k.htm
Link to new solenoids: http://www.transmissionpartsusa.com/A4LD_transmission_solenoids_switches_s/11567.htm

I only say all this because I think the solenoid may be at fault, but my previous post evidences that there could be other issues instead. Find out first if the PCM is firing the solenoid.

 

[rodb]

Thanks for all the info, looks like there is a lot to learn. If one of these sensors or solenoids were bad would it trigger a code? I am not familiar with OBD 1 and need to learn how to retrieve these codes.

 

[arco777]

Thanks for all the info, looks like there is a lot to learn. If one of these sensors or solenoids were bad would it trigger a code? I am not familiar with OBD 1 and need to learn how to retrieve these codes.

They might. Refer to where it says "Diagnostic Trouble Codes: ###" in the pictures I posted. Is your Check Engine Light (CEL) on?
Codes may be stored in memory even if the light is not currently on. You should pull the codes, then run KOEO and KOER tests.
Pulling stored codes is as simple as finding the diagnostic connector under the hood, grounding one specific wire, then turning the key on and counting the CEL flashes. An easier way is to buy an inexpensive Ford code reader ($35ish). If you do a forum search, the procedures to run codes are documented.

 

[rodb]

After reading on how to pull codes, it says to have a warm engine, problem is I have another issue that preventing me from getting engine up to temp. I also now have either some mechanical or vacuum noise under the hood which is hard to figure out where this noise is coming from. This truck has had numerous issues since I inherited about 4 years ago, so frustrating.

 

[larrydd999]

IMHO I wouldn't worry about having a warm engine. Just ignore the codes that say the coolant temp is out of range and such. You're looking for transmission related codes. I've used my code reader with a cold engine numerous times when verifying something. (There are, however, times that I yearn for the days of using a timing light & dwell meter, a VOM, and a screwdriver to adjust the carburetor...)

 

[arco777]

Agreed with LarryDD999. Ignore the inevitable code that pops up for "coolant temp lower than expected".

 

[rodb]

I did both tests, the only code stored was 66 which I believe is for the MAF sensor which should have nothing to do with my issue. I pulled the VSV sensor, the ohms read were 210 which should indicate that it is ok. Also noticed the electric shift fuse is missing under hood fuse box, whats that for?

 

[rodb]

To MrShorty, this was from one of your earlier posts: I would start this by probing the 3-4 shift solenoid circuit with a voltmeter and test drive it. You will be looking to see if you can see when the computer commands the 3-4 shift, and when it commands the 4-3 shift. If the actual shifting matches up with the computer commands, then you will be looking for a problem in the engine management system causing the computer to choose to go in and out of 4th gear. If the actual shifting does not match the computer's commands, then the problem is something inside the transmission.

How to I probe this circuit while driving ?

 

[arco777]

How to I probe this circuit while driving ?

Pull the passenger side kick panel off, unbolt the PCM bracket, set PCM on the carpet, and back probe the appropriate pins on the harness connector with a multimeter or test light. That's what I do anyways.

 

[rodb]

Thanks for the location of the PCM, having a hard time finding the pinout of the pcm for my '91 OHV.