A4LD speed sensor causing erratic shifting?

[mechjames]

Just a simple google search brought me here:

http://www.usatransdoctor.com/DomesticFORDselectandAnswers.htm#A4LD

If the vehicle speed sensor goes bad it can cause a no 4th gear symptom.

Under light acceleration, The transmission goes 1,2,3rd a bit, then to OD. Under full acceleration, it will go 1,2,then straight to OD.

My speedometer at above 60-70km/h will start to bounce around erratically. Explorers have an electronic speedometer if it has a speed sensor, correct?

I thought it might have been a long trip I took a few months ago, had a lot of overheating and mountain pass climbing. I've changed the modulator, and dropped the pan today. Fluid is clean, and the transmission was supposidely rebuilt 1.5 years ago when I put it in.

I did forget to put the magnet in the pan it seems when I changed the filter before installing it last summer. There is about 3 specs of metal I can see in the pan. Break in for the rebuild? I'm going to go and pick up a magnet, new filter and gasket when I do reassemble. Originally I dug into the pan to make sure the connections to the solenoids were nice and tight.

So speed sensor looks like its acting up, will it cause trouble with the 3-4 shift on my A4LD?

 

[MrShorty]

Explorers have an electronic speedometer if it has a speed sensor, correct?

Not necessarily. My '92 has a cable driven speedometer and a VSS. I'm not sure when they did away with the cable, but it was after '92.

So speed sensor looks like its acting up, will it cause trouble with the 3-4 shift on my A4LD?

A bad VSS can/will cause trouble getting it to shift into 4th gear.

 

[mechjames]

Pulled the VSS today, picked up a new one. Broke the bolt that clamps it in. Now I have to try and drill, and retap. I noticed there wasn't any fluid coming out of the VSS hole. I'll check the transfercase fluid, Its probably because its jacked up at a weird angle.

Might put insurance on my truck this weekend and see how she drives.

 

[BrooklynBay]

Pre 92 Ford vehicles with a digital dashboard have no cable connected to the VSS. My 89 van is one example. My 93 van has an analog dashboard, and no VSS on the transmission. It was replaced with an ABS speed sensor on the top of the differential. This sensor uses the hall effect to create a stream of pulses. # 3 in my list of useful threads has more information: http://www.explorerforum.com/forums/showthread.php?t=158739

 

[mechjames]

My 94 has the mechanical speedometer cable connected through the vehicle speed sensor with two wires.

Thanks for the informative writeup. I now believe my torque convertor lockup is coming on way too early, creating the clunk during shifting.

I'll report back when I get the speed sensor clamp hole drilled out and the new sensor installed!

 

[BrooklynBay]

You could use a tool like this to remove the broken bolt: http://www.google.com/products/cata...0CB8QzAMwAA&cid=386379265226603995&sa=image#p

 

[mechjames]

That's a good tool, I'll go see if the local auto parts store has one in the right size.

I have used similar things for removing stripped screw heads. They work well.