Possible transmission Solenoid failure

[landyacht318]

My TX has only 2 solenoids, one for Overdrive one for the torque converter lock up. It is a chrysler A-500 from 1989, also called the 42-RH. Basically a 904 with a overdrive housing tacked onto it. The 904 is the venerable 727's baby brother.

When the TX is cold, it shifts into OD no problem.
Once warm, at 35MPH, it will fall out of overdrive, then back in,out,in, out, quickly, until I hit the OD off button.

Speed upto 40 MPH and release OD off button, and sometimes it will go into and stay in OD, other times it will not engage until at a higher speed and will not drop out.

I checked most of the wiring harness, not finding anything that cried Eureka, but Got Deoxit on all connectors and cleaned up and wires in split loom and routed cleanly.

The Solenoids are controlled by the 1989 ( remanufactured) engine computer.

The engine computer decides based on engine speed sensor in distributor, the throttle position sensor, the coolant temp sensor and the Manifold absolute pressure sensor.

The TPS could have a flat/intermittent spot on it in that 35 to 40MPH range. Will check tomorrow. It could be original and nearly 30 years old.

Trying to figure out a methodology to isolating the issue before dropping the pan and valve body and replacing the two solenoids.

Perhaps backprobing the one connector with 3 wires leading to the solenoids and seeing if the voltage is intermittent at that speed, or perhaps feeding 12v or maybee just 5V directly to the solenoid at 35 MPH when it is kicking in and out, and seeing if it still occurs.

It could be mechanical in nature too, but I have been rather maintenance minded with this TX, with additional cooling capacity and extra filtering, and regular fluid changes with the proper fluid, and would expect much more mileage on this rebuild before any mechanical issues cropped up. Last June I had the pan down and there was only a slight ferrous sludge on the magnets ands the fluid was still pink and smelled sweet. Only racked up perhaps 3500 Miles since.

Any Ideas for diagnosis?

Or perhaps somebody familiar with chrysler transmissions from this era. 1989 is the first year the A-500/ 42RH was offered, and lasted to 2004, with some changes regarding the electronics and hydraulics.

[landyacht318]

I know All ATF+4 has to have the same lubrizol additive package and certain quality basestocks, before it can be called and sold as ATF+4. If WW had the supertech version ATF+4, I would have bought it.

All other Ap stores which sell ATF+4 was 1.50 to 2$ more expensive per quart.

Utimately I could have ordered online and saved a few bucks but at the time, I thought I needed it tomorrow.

While at first, I though driving around locally my MPGS were not affected by disabling the overdrive, but when it was time to put 20 more $ in the tank, the Odometer was reading 15 less miles accummulated than usual. 3rd gear at 35mph is 1850 rpm, in OD it is about 1200, and drops when I take my foot off of the gas to coast.

[bucky]

Wally now has ATF-4 in their house brand, at least in our area. Glad you got it working, things can be maddening sometimes.

[MEXICOWANDERER]

GO GOOGLE for genuine MoPar ATF4.
Found case lots less expensive than Wool-Mart

[landyacht318]

As an Update:

I decided to go ahead and get new solenoids drop the pan and valve body and just do it.

In preparation for dropping the valve body, I spent some time cleaning the TX above the pan, where the electrical connector and shift lever exits the transmission. Brass Bristle brush, spray silicone, rags q tips and compressed air to really get things spotless.

While doing this, I remembered that I never bothered resetting the engine computer, after rebuilding the wiring harness and lubing Speedo cable and inspecting VSS, and did so.

Since the exterior cleaning, but more likely the ECM reset, Overdrive has been working as it is supposed to, for 2+ weeks now.

Valvoline ATF+4 is $6.50 a quart at wally world. I might return it, I might use it. I am going to await the return of symptoms before doing anything else.

[landyacht318]

King of the Slackers has put off lubing the speedo cable, so far.

I found my username and password for Allpar forum and the responses to my issues brought up the possibility that the OD and lockup solenoids, which are on a plate held on with 3 bolts, could have had the 3 bolts loosen up, as others have reported this happening on this specific transmission and the leakage around the solenoids when the ATF is warm, would cause the dropping out of OD.

The general consensus is that this is more likely than a fault in the wiring from ECM to solenoids, which means I will likely drain my pan then drop it and see if the bolts are indeed loose.

But if I am going this far Perhaps I should just order new solenoids for ~50$ and drop the vlavebody and replace them while the pan is down.



Part of me also wants to simply rig up 3 T10 light fixtures and put LEDs into them. One bulb would indicate whether the 12v feed is intermittent, the other two wires are switched grounds for the OD and L/U solenoids. If the bulbs start flashing then I could perhaps avoid an unnecessary pan drop.

It also seems that once the ATF is warm enough that the OD is not engaging under 40MPH, that lockup will not occur under 55mph, where it always would occur at 47mph if accellerating slowly.

Perhaps L/U does not occur over 55mph once warm either. traffic impeded this portion of the test yesterday.

Heres hoping for a nice clean pan when I do drop it. I'd love to find loose bolts.

Replacing the solenoids requires dropping the valve body to remove and replace the electrical connector.

[j-d]

landyacht318 wrote:
Also suggested my Speedo cable can be in need of lube, and bouncing. Vehicle speed sensor is inline on Speedo cable. Will relube tomorrow.

We bought a used 1985 Olds Cutlass that was very clean with low miles. It ran well but at certain speeds the engine had a rolling stumble kinda feeling, especially on OEM cruise control. I thought it was something about the "Buick231" V6 lacking V8 smoothness.
Decided to lube the speedo cables. One from transmission to cruise module, then module to speedometer head. Inside the car, near the speedo head, I found this odd looking mirror thing, like a two-bladed pinwheel, that rotated with the cable.
Apparently, it and a little photocell kinda thing, made up a primitive VSS. It was speeding up and slowing down with the sticky cable! Lubing it fixed the cruise and the engine quit stumbling.

[MEXICOWANDERER]

Allpar.com was one of the first, perhaps the first online forum I joined. Can't remember my username or password though. I think about 10 years back they kept having so many issues with the site I stopped visiting. DO not really remember why.

They had sign-in problems

Not
Any
More

The site has gained some top-notch techs and it would be an eyebrow raiser if you do not regain name and password and drill right to the precise troubleshooting list they will offer. It's a different ballgame now.

[PaulJ2]

My guess is not an electrical problem at all. Low line pressure. As the oil warms it looses some of it's viscosity which is normal. Either internal leakage somewhere or may be a worn pump.
The clue is the problem gets worse as it warms. My thoughts.

[landyacht318]

If the solenoid were failing, then it would not just engage and disengage at only 35mph right? Today I was holding 40MPH warm and OD stayed engaged, acted normal. Did not get it upto lock up speeds(47mph+)

I checked resitance on the throttle position sensor through outs its range. Very smooth, but I do not know if the resistance range is correct. 1.36K ohms to 4Kohms.

Manuals say to check voltage output through range. Backprobing connector proved curse inducing.. DO not want to pierce wire insulation.

Also suggested my Speedo cable can be in need of lube, and bouncing. Vehicle speed sensor is inline on Speedo cable. Will relube tomorrow.

[road-runner]

j-d wrote:
That link above implies that this transmission uses more than just two solenoids, but maybe MoPar phased more of them in during its long production cycle.

After I read the linked article, I went on to read about a ZF transmission I'm familiar with. Its article strongly recommends band adjustments. The problem is that this transmission does not use bands, having replaced them a few generations earlier with braking clutches that are not adjustable. My impression of the site's usefulness went to zero.

When I had a '87 Dodge I was questioning if the torque converter was locking. I tapped the wire for the lock solenoid and ran it to an LED inside the cabin. (I know this verified only the electrical part, not the mechanical).

[j-d]

That link above implies that this transmission uses more than just two solenoids, but maybe MoPar phased more of them in during its long production cycle.

A little disappointed it's based on 904 not 727, but oh well.

There's a transmission forum on BAT Auto that might help.

Please make CERTAIN SURE the TQ is locking when it should! If it's not locked at cruise, transmission will overheat and fail.

[westend]

First diagnostic point I'd go to would be resistance at the solenoid leads. Those values should be published. You could also measure voltage across the leads when running. That may unearth a faulty/failing solenoid or an "open" in the circuit.
Coincidentally, I have a failing TX solenoid in a Subaru, ATM. I plan to pull it, clean it, and measure resistance, along with testing for functionality. The price of a replacement makes my cheaper method worth the effort.

[landyacht318]

Allpar.com was one of the first, perhaps the first online forum I joined. Can't remember my username or password though. I think about 10 years back they kept having so many issues with the site I stopped visiting. DO not really remember why.

Was in some other Dodge related forums but all it took was one insufferable feminine hygene product and the bag it comes with to get me to remove those bookmarks.

The Solenoid wiring has 3 wires. I will assume one is a ground.

I am thinking about backprobing the connector at an easy to reach location with some T10 bulb receptacles, that way a steady light bulb will mean the ECM is sending a steady signal, and a flashing light means it is not, and I will not have to drive and hold voltmeter leads at the same time.

Replacing the solenoids means dropping the pan and valve body. Never dropped the valve body before, but I do not just want to throw parts at it and pray.

Later versions of my transmission have more solenoids and much of the info I find is for them in later model vehicles.

So where I am at, is thinking I need to determine if the solenoids are getting a solid or intermittent signal, and go from there.

From this forum i was hoping more to understand how solenoids fail, and their behavior when they reach the end of their useful life. I am not going on any roadtrips where overdrive and lockup are required, aI can simply lock it out of overdrive, so I do have some time to deal with this issue.

I do fear if it is mechanical in nature that I am grenading the transmission by continuing to drive it though.

[djsamuel]

MEXICOWANDERER wrote:
Postively superb free forum techs at

Http:www.allpar.com

Tech Forum

Especially Imperial Crown

Fussy me --- this is one of the far too scarce expert forums online. It never fails to impress the hell put of me.

Allpar is a great site and Imperial Crown always seems to have a great answer.