No Shift and no Speedo

[mr_smith]

91 f250 2wd e4od

I suspect it's in limp mode.. It doesn't shift and only does about 35 mph, which is a guess because the Speedo is not working.

It also felt like it was slipping at high rpms..

I did some searching and the best I came up with is that the VSS is shot..

Is there a fuse or a code I should be looking for? Is the VSS on the diff on a 91?

Thanks!

 

[mr_smith]

I was doing some more reading and apparently the '91 has a cable.. Does that mean my trans issue isn't the vss?

 

[vegas39]

The vss is mounted in the trans cable, at least that's how it was on my 89. It controls the cruise control also. If the speedo quit and your trans is acting up, I'd say something broke somewhere, either the cable or something in the speed sensor

 

[Robby]

My trans done the same thing when the ECM relay was bad. Got one from O'Reillys for 15.00 bucks. Took care of the problem. I keep a spare on the truck now.

 

[mr_smith]

So if I replace the cable the vss will be part of it?

 

[vegas39]

No, the cable screws to it.

 

[mr_smith]

The only VSS I can find is the one that goes on the rear diff..

 

[trackspeeder]

The only VSS I can find is the one that goes on the rear diff..

That is the ABS sensor.

The VSS is at the end of the speedometer cable. You will need to remove it to pull the cable out of the tranny. No speedometer or VSS operation means the cable or gear is bad.

 

[gandalf]

Does the '91 have a cable driven speedometer? I know my '92 has an electronic one. I'm not sure when it changed.

Anyway, I'll post a picture of the differential on my '92, along with the electronic connection. I've always been under the impression that was the VSS.

You must be registered for see images attach

 

[snicklas]

Brick down 91 and older has a cable driven speedometer. If it is an E4OD equipped brick, there is a VSS in the speedometer cable to run the TECA, and a VSS in the rear diff to run the RABS.

92 and newer (I know through the 6.0 trucks) there is only a VSS in the rear diff that is the signal for everything.

 

[Macrobb]

Brick down 91 and older has a cable driven speedometer. If it is an E4OD equipped brick, there is a VSS in the speedometer cable to run the TECA, and a VSS in the rear diff to run the RABS.

Also, there will be a VSS if it is a manual with cruise control - they use the same sensor for that.

(Interesting note - even once they switched to the newer rear diff sensor, the "VSS" pulse signal that runs the cruise control(and probably the E4OD) is the same. You can retrofit a newer cruise control module onto an older truck, using the stock cable-driven VSS. I'd bet you could use the diff sensor on an older truck if you used a newer-model PSOM for converting the signal, as well).

 

[mr_smith]

I guess the big question is where do I start? I really don't want to just throw parts at it..

 

[madpogue]

If the speedo's not working, I would suspect the drive/driven gears for the speedo cable. That would render the speedo inop, and would mean the VSS would not be reading any speed.

 

[trackspeeder]

I guess the big question is where do I start? I really don't want to just throw parts at it..

Start by removing the cable from the tranny. The cable enter the extension housing on the driver side. Remove the bolt and work the VSS out of the housing. Be careful not to break the sensor in the housing.

Once you have the sensor out, you will see the drive gear for the speedometer. If it is stripped most likely the cable is bad. If it is not stripped check the cable anyways. It still could be bad.

The fun will begin if both parts check out good. Time to pull the extension housing. The worm has broken or is stripped.

 

[mr_smith]

Start by removing the cable from the tranny. The cable enter the extension housing on the driver side. Remove the bolt and work the VSS out of the housing. Be careful not to break the sensor in the housing.

Once you have the sensor out, you will see the drive gear for the speedometer. If it is stripped most likely the cable is bad. If it is not stripped check the cable anyways. It still could be bad.

The fun will begin if both parts check out good. Time to pull the extension housing. The worm has broken or is stripped.

I pulled it out, the square drive part looks fine.. How do I test the rest of the cable??

Someone above said they had to replace a ecm relay.. Could that be the problem?