E4OD, anyway to bypass VSS switch on differential?
 

I have a 1994 F350 with a E4OD and the trans started acting up, the speedo went out and the trans started doing all kinds of funny stuff and I have narrowed it down to the VSS in the rearend.

Is there anyway to bypass the switch and get the trans to work correctly? is it me or should a 10$ plastic part not have this kind of control over a machines operation.

Thanks for any help.

That part will kill the tranny too if you don't fix it, thats the only thing that tells the computer how fast the truck is going, it like you driving with your eyes closed, wont be pretty.

As for a 10 dollar part, that is going to be garbage at that price, if you want it to work and last a long time, go get an oem one and save your self the hassle of crap parts

Before doing any of that, pull the sensor out the diff and make sure its clean, can be something that simple

Thanks, there are no descent after market parts?

Before you start down this path further please explain how you "narrowed it down to the VSS in the rearend." ?

They rarely go bad, it's usually a wiring issue or something else is dragging down the signal (RABS, Speed Control servo) or the PSOM is bad.

In the event it is a faulty VSS it is highly recommended to use an OEM replacement. Yes, the aftermarket versions are that bad...

The VSS sensor is fairly common to go bad

I will kindly disagree :-drink

I know I have replied to many posts where the OP stated they already replaced the VSS but still have the same issue. Yes, they do go bad but before spending the bucks on one it is easier on the wallet to look at the other more common causes.

I think subford holds the record for most "assists" with this issue!

Thanks for the replies, the speedo and eletronic mile gauge quit working.

start with the basics.check your fuses.

people often replace them.however most of the time needlessly.

Agreed.

You can use a scan tool that accepts DTC input to verify if the ECU is getting a speed signal (MPH) input.

Quit working like no needle movement and blank odometer display? If so check fuses 8 and 18.

It is almost imposable for a VSS to go bad unless you break it while removing it or it is hit by something in the rear end.

Sometimes it has been installed wrong with too large a gap or has something build up on it as it is a magnet.

Not sure how it would loose it magnetism but that may be possible somehow.

If someone or some part in the PSOM or RABS puts power to the VSS wires that could burn open the coil in the VSS. The VSS supplies its own power.

The VSS just consists of a permanent magnet, a ferromagnetic pole piece, a pickup coil, and a rotating toothed wheel. No moving parts in the VSS.
As the tone wheel teeth of the rotating tone wheel pass by the face of the magnet, the amount of magnetic flux passing through the magnet and consequently the coil varies. When the tone wheel tooth is close to the sensor, the flux is at a maximum. When the tooth is further away, the flux drops off. The moving target results in a time-varying flux that induces a proportional voltage in the coil. Subsequent electronics (PSOM & RABS module) are then used to process this signal. The PSOM then drives the Speedometer, updates the mileage in the LCD odometer display and the EEPROM and sends a digital waveform to the Speed Control and the PCM Computer..

I am speaking from personal experience.

I have replace at least 50 VSS sensors and it fixed the speedometer issues, shifting issues or other related issues. Out of the 50 or so that I have replaced, not ONE did not fix the issues.

When you work at a dealer, you see all sorts of common issues

You realize what you are saying goes against just about all of the post on this subject in this Forum in the last 7 years that I have been reading.

I have also fixed numerous problems with the PSOM signal going to the transmission and speedometer and I did not replace one VSS.

What you are saying is very hard for me to believe.

it doesn't make any sense because that's not a ware item.if the 50 replacements cured the shifting issues,then more than likely simply cleaning the sensors,rather than replacement would have done the same thing.it's actually pretty easy to know when one is in need of cleaning,as the speedometer needle will be bouncing.once it gets so bad,it will start to frig up the trans operation because the control unit can't read the speed accurately.
however i can easily see how a steelership wouldn't bother with such things.they would want to simply change the sensor so they could charge for the part and the labor to replace it.they didn't get their derogatory nickname for nothing.

OT question, could a early TC or tail housing be swapped in and the speedo pickup version used instead to get the sensor off the rear end?