I have some serious tranny issues and there is a used, apparently rebuilt E4OD transmission in my area I could probably pick up for around $300. Im wondering if anyone here could give me some advice on whether or not this would be a good investment, even if just for just parts.
So my transmission is acting weird, that’s the way it came when the previous owner gave me it. He told me someone burnt the overdrive gear by forgetting to turn it off while towing a camper. However the overdrive gear still works but just shifts in and out from 3rd to Overdrive erratically somewhere between 60 – 70km/h, affected slightly by pedal play.

At first the original owner suggested that I just leave the OD off all the time unless I’m doing +80km/h, worked well for the first few months of driving. Then I started to notice that the transmission would only go into 1st gear early in the morning when still cold then after it warmed up it would never drop below 2nd gear. So I started driving the automatic like a stick and everything seemed to run smoothly once again. Until recently gears have started slipping, 3rd will slip at around 60km/hr and second somewhere around 45 km/h.

I should mention that since day one the speedo has been out the window, and I have been driving without a PSOM Fuse. When the fuse is in the needle bounces erratically around the dash becoming more erratic as speed increases. So all the speeds I quoted earlier are simply estimates. I also noticed that the transmission seemed to shift rather uncontrollably as the speedo bounce all over the place. I figured that the transmission was people getting readings from the speedo so I pulled the PSOM fuse and the transmission calmed down considerably but still has problems.

I went out and replaced the TPS (Throttle Position Sensor) but that didn’t seem to help, so I removed the VSS (vehicle speed sensor) it looked brand new, just like the TPS. So I chose simply clean it and replace it, also did nothing.

So I think I’m looking at two different problems here. A transmission problem unrelated to the PSOM, VSS, & TPS, seeing as how even with the PSOM fuse pulled I have problems. The second being a PSOM problem which could be sending bad signals to the tranny when plugged in, I think this could me a bad PSOM or a bad exciter ring in the rear diff.

Any thoughts!? What should I do?

 

Why have you not pulled the codes yet?

 

Oh, forgot to mention.

I pulled the codes, the only one I got was bad TPS, which I still got after I replaced the TPS. I will pull the codes again and get back to you, I never did a engine running code test

 

The PCM uses the PSOM signal as a reference to control the transmission and shift points. Without it you stand a good chance of ruining that transmission. Really surprised there are no codes related to a missing VSS signal. A replacement transmission is not going to last long until you fix the input signal problem(s).

 

The PSOM feeds both the speedo and the PCM and that input is critical to correct operation of both things, and it sounds like yours is bad so maybe start by replacing the PSOM and see what that does.

 

OK so I did some major testing / diagnosing today in an attempt to pinpoint the problem.

First thing I did was pull the codes, and came up with this;

Key On – Engine Off - 23, 14, 29, 67
23: Throttle Position Sensor Out Of Range; (Seek professional help)
14: Erratic Ignition Pickup; (No idea what this means)
29: Bad Vehicle Speed sensor; (Maybe the sensor really is bad)

Key On – Engine On – 93
93: Binding Throttle Linkage or Bad ISO Motor


So then I moved on to the VSS I tested for resistance and got 1728 Ohms which exceeded the 800-1400 Ohm rating. Then I tested the resistance at the PSOM connector on Pin 21 Green/Black & Pin 22 Red/Pink pair and got 1660 Ohm which also exceeds the 800-1400 Ohm rating. What I don’t understand is how could the resistance here be less than the resistance at the sensor, shouldn’t it be higher after factoring in the wire length?
After that I went to the 4WABS located behind the Left Headlight, which in another diagram located on the Left Inner Fender is labelled the TFI? Anyways the resistance here between the Green/Black & Red/Black Pair (the same color pair which leave the VSS) is 0.3 Ohms which is below the suggested 5 Ohms.

Next I jumped in the cab and performed a PSOM check by holding the reset, starting the vehicle, and releasing. The needle went all the way up then the odometer displayed “ o 03” Not in the standard “E 08 06” format I had expected.

Next I jacked up the rear end and went back to the VSS, disconnected it, and used a graphing multimeter and measured a smooth increase in signal relative to increase in wheel speed.

After that I measured both the millivolts and Hertz at the VSS at four different speeds to determine if the output was greater than 6.0 mV/Hz.
Here’s what I got;

1st Gear, @ Idle Speed: 500mv/125Hz = 4 mV/Hz
1st Gear @ Increases Throttle: 750mV/180HZ = 4.2
2nd Gear @ Idle Speed: 800mV/220Hz = 3.8
Drive gear @ Idle Speed: 750/180 = 4 mV/Hz
Reverse Gear @ Idle Speed: 650/165 = 4 mV/Hz

Which are all consistently lower then 6.0 mV/Hz.

So it would seem that by failing both the resistance tests and the output test the VSS seems shot. But I was thinking that with a greater than allowable resistance that may be what is causing the smaller voltage readings, and therefore causing the smaller output (mV/Hz) readings.

The only other thing I could imagine causing this would be excessive spacing between the exciter ring teeth and the VSS sensor causing a drop in voltage due a greater distance between the magnet in the VSS and the tips of the exciter ring teeth. But it seems unlikely and probably due to the increased resistance of the sensor. But one thing I still don’t understand is how the resistance is less at the PSOM?

So im thinking that maybe tomorrow I will drain the rear-diff, check all the exciter ring teeth, remove metal flakes, refill, and re-check resistances.

On another note none of this really explains the erratic speedometer, especially after a graphing multi-meter showed me a smooth increase in signal frequency relative to wheel speed. I think I need a new PSOM but for tonight I am going to look into testing one. Would a Bad PSOM send my OBD a bad VSS code?

 

So I went back after I read not to tip the speedo upside down due to the possibility of leaking settlement fluid and I found this!

The inside of the housing was scorched black likely from carbon due to something combusting.



I compared it to the parts on the back of the PSOM and found that the little black vertical disc, the little battery to its right, and the metal thing below both of them all line up.



The weird thing being, none of them show any sings of burning or damage.

 

Well my camera is too ****ty to pull off macro mode or produce any cleaer shots. But I've made some progress regardless.

I determined the the little black disc to the left of the battery shaped resistor is in fact blown.

Under a magnifying glass its clear that something combusted inside than shot out and upwards where their is a thin slit in the back heat shrink type material sorrounding the resistor.

When I tested all the other battery shaped resistors on the PSOM card I got resistances of around 26 kOhm or 28 MOhms, when I test the black disc, I get a resistance of 0.6 Ohm, seems rather small.

So I took a closer look and pulled the numbers off the black resistor, they read;

08131
E3SF - AA
T D K

So I called up TDK and they confirmed it is in fact a resistor, and it should be located near the MOV1, which is exactly where it's located but they couldn't find anything that would come up with said serial number.

After a rough identification via diameter (14mm) we came up with this one;Part #: P7308-ND

Digi-Key - P7308-ND (Manufacturer - ERZ-V14D270)

Looks similiar but no idea if it's the right one as per specifications. So now I am going to go back into the vehicle and measure the input voltage to the resistor and this should help to narrow down the possibilities. Then I am going to short the two terminals of the resistor affectively bypassing it to see if that solves my jumping speedometer problem.

 

So after some furhter research I have determined that the blown part is a
TDK Non-Linear Lead Varistor. It's essentially a surge absorber, as voltage goes up so does the resistance.

So I found out that TDK no longer produces these but their EPCOS division does. After a quick product search through non-linear varistor's with "Automotive" and "12V" as my only search parameters I was turned up with the following;


http://www.epcos.com/web/generator/Web/Sections/ProductSearch/Hitlist/NonlinearResistors/Varistors/Page,locale=en.html?param_application=Automotive&p aram_v_rms=&param_i_max=&param_w_max=&param_headli ne2_en=Automotive&param_type=&from=searchform&doAc tion=searchform&view=&distributorId=0&cssurl=&shop =no


Next I Pulled up the specifcations for the varistors series and compared physical size to the guide, found here on page 5.


http://www.epcos.com/inf/70/db/var_11/SIOV_Leaded_Automotive.pdf


w = 15mm
h = 17mm
th = 4mm
[e] = 7.5


Must be " B72214S1140K501 " RESULT!


Specs:


B72214S1140K501 S14K14AUTOS5D1 14VAC 16VDC 1000A 4.0J


http://search.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=B72214S1140K501


All specs seem within reason, this must be the right one. I wonder if it will fix the jumping speedo problem?

 

Alright so I found a very similiar Varistor the only difference is current surcharge is rated for 250A instead of 1000A, should be fine considering the PSOM power is shutoff while cranking.

I took some voltages at the PSOM from the VSS this morning and got the following;

0.57 VAC @ Idle
1.36 VAC @ 30 km/hr
1.80 VAC @ 60 km/h
1.925 Vac Max

1.8 VAC was within the perscribed 0-3.5 VAC while running at 50 km/h
And a MAX VAC of only 1.9 was kinda low.

So I went back to the connector and looked over the wiring to find 3 splices on each line within a 2 feet of the VSS and a few exposed copper sections, corroded a nice green. Maybe it was due to the dirt which had somehow completely filled the plastic cable gaurd.

I traced about 70% of the cables (LGreen/Black & Red/Orange) across the chassis up through the firewall and into the PSOM connector. I go to take some new readings, BAM, no continuity! And my speedo won't work, but VSS is producing.

So I am wondering, did I miss anthing when tracing the wires or do they go straight from the VSS to the PSOM? Im pretty sure my 92' F350 Cust. has no ABS.

So I cut the VSS plug out with about a foot of wire, stripped the green one all the way to the plug, completely burnt!

So whatever blew the Varistor in the PSOM went straight back to the VSS.

Does anyone know where I can get some wiring diagrams for this?

 

What you are looking for is called an EVTM (Electrical Vacuum Troubleshooting Manual). I bought my last set of CDs on E-bay for $10.

You other question about the VSS signal: It goes to the RABS module then continues on to the PSOM. Yes your truck has anti-lock brakes, but only the rear.

This diagram from Steve83 may help you out with your issue: 1983 Ford Bronco PSOM picture | SuperMotors.net

Please note the VSS output signal in the caption: Does the voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle speed increases from 0 to 48 km/h (0 to 30 mph)?

Your value is too low.

 

Trying to make heads and toes of this diagram.
So one of the splices I encountered were factory for extending the harness length. Whats the dotted line that crosses the parallel circuit after the VSS?

Is the RABS Module the actuator valve located on the drives side inner frame rail?


Whats with the "Gasoline Engines over 8500 GVW" What is neglected from my diesel?

Why are their two PCM's?

Whatever power surge fried the varistor in the PSOM and travelled through Green/Blk all the way to the VSS possibly went to the RABS Connector and Module as well. So I geuss its back to tracing more wires.

Does anyone have a circuit board schematic for the PSOM's solid state drive? or any idea how I can test it without a breaker box, perhaps by sending varying AC signals into it and observing needle fluctuation.

 

So I got everything put all back together. New tone ring and diff cover sending a solid speed signal with only one snare, little jump in the needle visibile over 100.

So now the TPS is set perfectly, the VSS signal is sending, I cleaned all the connectors in the truck, except one that's melted together well get to that later.

I performed a Engine Running Code Test and sure enough their was no signal from the RPM sensor at idle and the computer ran a KOEO test. I hooked up a graphing multimeter and looked at the waveform, similiar for the VSS. Their is no frequency at idle, explaining the no tach reading under 1000. As I stepped on the pedal the waveform appeared. But it was erratic with snares everywhere, completely undeicpherable.

Now that would lead me to belive that the teeth on the ring are damaged but I dont think this is the case. Would the waveform be erratic because the teeth pass the magnet on the diagonal instead of perpendicular?

I've got a closed circuit at the dash for the RPM Sensor, but when I tried to do a Resistance test of the sensor away from ferrous metals I couldn't get my meter to settle on a reading.

I can't imagine how this sensor would go bad being just a magnet. Their was a small section of exposed wire at the base of the sensor, this could be a problem but I insulated it, unless it has become slightly detached making it harder to send a smaller AC signal.

All the wiring looks good to the dash and I believe the RPM Gauge is good. But I dont understand why the RPM needle doesnt wobble when over 1000 it should considering how glitchy the AC waveform is. And still no low voltage AC signal being detected.

 

If you can't get the proper voltage output directly at the 2 pins of the VSS (with cable disconnected at the sensor) either the sensor is bad, the air gap between the exciter ring and sensor is to large, the exciter ring is damaged (you said you replaced it) or the ring gear or tone ring has to much run out.

Below is the air gap and ring gear run out specs.

Programmable Speedometer/Odometer Module- Pointer Waver-Service Tip
Article Number 96-21-11

LIGHT TRUCK:
1992-96 AEROSTAR, BRONCO, ECONOLINE, F-150-350 SERIES

ISSUE:
The speedometer needle may waver and/or a light surge may occur on some vehicles when speed control is used at highway speeds between 80-113 km/h (50-70 mph). This may be due to slight dents/chips in either the exciter ring or the Vehicle Speed Sensor (VSS) and air gaps between the VSS and the exciter ring.

ACTION:
Replace the Programmable Speedometer/Odometer Module (PSOM) if required. New PSOM's come with increased immunity to system variability. Refer to the following Diagnostic Procedure for details.


DIAGNOSTIC PROCEDURE

BRONCO/F-SERIES - Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 F-Series/Bronco Body/Chassis Service Manual, Pages 13-01-30 through 13-01-32 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-11.

ECONOLINE - Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 Econoline Body/Chassis Service Manual, Pages 13-01-29 through 13-01-31 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-9.

AEROSTAR - Perform normal PSOM diagnostics per Pinpoint Test "K" of the 1994 Aerostar Body/Chassis Service Manual, Page 13-01B-31.

1. Any slight dents, chips, etc., in either the exciter ring or VSS will create needle waver. Measure air gap between the VSS and exciter ring. It should be 0.38-0.51mm (0.015-0.020").

2. Check exciter ring runout per the same ring gear backface runout procedure of the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-00. Make sure the exciter ring is mounted correctly to the ring gear. If runout is more than 0.1mm (0.004"), perform the differential runout check per the procedure in the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-02A or 05-02D, to find cause and repair as needed.

3. If all items listed above check good, replace the Instrument Cluster Assembly. Obtain the correct service part number from the Parts Catalogue and then contact the Electronic Odometer Exchange Center at (800) 259-9700 for U.S. Dealers and (800) 663-9974 for Canadian Dealers.

NOTE:
DEALERSHIP MUST TELL THE ODOMETER EXCHANGE CENTER THAT YOU NEED A PSOM3 LEVEL CLUSTER FOR A SPEEDOMETER NEEDLE WAVER CONCERN.

OTHER APPLICABLE ARTICLES: NONE

WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

 

I pulled the codes again and I got Error Code 14 again, but all the other codes were gone after cleaning solenoid pack connectors.

OK I'm a little puzzled here, and I need to be more certain of what's going on before I go and pay the $100 for a new tach sensor.

I removed the sensor and repaired any damaged wiring. Tested for resistance and continuity, nothing.

I pluged it back in and scoped it at the sensor output. Their is a voltage and frequency output at idle and both increase smothly with acceleration. I used the VSS Sensor test on the scope to compare the voltage and frequency. Hate to say that everything looks fine here, but is this possible without continuity between my sensor probes?

Followed the sensor wires back towards the passenger inner fender wall at the connector, cleaned it. Took readings there at idle and got 155 mV @ 550 Hz. From their they dissapear again behind the right headlight and I can't find those colors again anywhere else.

I jumped into the dash and pulled the tachometer and looked at the three probes on the back (B+, Sig, Grnd) So I attached the probes to the Sig & Grnd assuming I should be able to get the same (or sampled) Frequency and voltage reading here as I did at the sensor. I got no frequency reading and not even 1 mV. Untill I started to accelerate and then when the engine sounded like it was about 1000 rpm, Boom, voltage and frequency showed up. But the wave form was not as it was at the sensor and certianly not a sample of the sensor. It was not sinusiodal like at the sensor but instead it was an exponential repaeating wave. So then I thought, well maybe the signal and ground input to the tach are not where I want my probes, pulled the entire console to look for the (Orange/Yellow & Green/White?) attached to the sensor end of the harness, but I couldnt seem to find any at the dash.

Now I know the computer is not recieving a Tach Signal at idle becuase when I went to pull the KEOR codes, it entered KOEO. Also I got a Error Code 14 (Erratic Profile Ignition Pickup) which a Ford Trans Tech mentioned he usually replaces the Tach Sensor when a Code 14 is present.

But it's clear that a tach signal is getting through and the gauge is working because I have full read of tach signal when deccelarating, only when accelerating ther is no voltage or frequency untill over 1000.

So where is this signal going from the sensor, where is it being modulated, and what the heck could possibly be causing that initial impedance at the gauge?

I need wiring digrams. I'm going to go take more readings.