VSS Replacement on a 89 2WD Automatic Trans?

[Ranger101]

My speedometer isn’t working and I get a long stall in the shift from 1st to 2nd. She also intermittently loses power in the city and on the highway. Can’t have that!

I want to start my trouble shooting by changing the Vehicle Speed Sensor first. Any help on locating it on the automatic A4LD transmission and any tips on what to look out for when changing it would be appreciated.

 

[scotts90ranger]

It's at the end of the speedometer cable going into the rear drivers side of the transmission, should be the only thing out there sticking out the side with a 2 wire connector on it too, I think it's a 7/16" or 3/8" hex on the bolt.

Sounds like your speedo gear might be broken or something, they're easy to come by and go by color for tooth count.

 

[RonD]

+1 ^^^

Look at the 3rd and 4th pictures here: https://www.therangerstation.com/tech_library/speedometer.shtml

You have a dual speed setup, a speedometer cable just for the speedometer/odometer, AND a VSS for the computer and cruise control(if so equipped)

If speedo is acting up AND you think trans is acting up then the problem may be the gear, so pull the unit out and make sure gear is OK and tight on the shaft

Speedo cables are made up of several smaller wires wrapped together, over time one of the smaller wires can break and cable will bind as it spins causing the speedo to jump around, as cable binds and releases
This can effect the other end of the cable at the transmission as well, so could effect VSS signal out to computer

 

[adsm08]

If you have any damage to the plastic drive gear rotate the cable by hand to feel for binding. I have had a cable bind, freeze, and wipe out the teeth on the gears.

 

[Ranger101]

Thank you all for the input and knowledge. I’ll put it in over the weekend and post the results.

If the smaller wires that make up the cable are the issue, how will I know that after changing the VSS and checking or changing the gear?

How do I change the speedo cable, if necessary?

 

[RonD]

Its for sure not just the VSS, that wouldn't effect speedometer at all

These dual units were used from 1987 or so to 1993/94 on all Fords so not hard to find them at wrecking yards and they were not known to fail, unlike the rear axle VSS stand alone sensor were

If the Driven gear(on the unit you pull out) looks OK then put it back in and leave speedometer cable unhooked, go for a drive to see if transmission shifts OK

You can use a drill on the speedometer cable to spin it, and see if the speedometer reads OK or gets jumpy, indicating a bad cable
It only shows speed in one direction, but doesn't hurt it to spin it the other direction, thats happens when you back up, so if speedo doesn't show speed Reverse the drills direction

To replace speedometer cable you need a new cable, of course, and you will need to pull out the instrument cluster, to unclip it from the back of speedometer
Have 6 new Cluster back light bulbs, as this would be a good time to change them all, they are not expensive

 

[Ranger101]

Its for sure not just the VSS, that wouldn't effect speedometer at all

These dual units were used from 1987 or so to 1993/94 on all Fords so not hard to find them at wrecking yards and they were not known to fail, unlike the rear axle VSS stand alone sensor were

If the Driven gear(on the unit you pull out) looks OK then put it back in and leave speedometer cable unhooked, go for a drive to see if transmission shifts OK

You can use a drill on the speedometer cable to spin it, and see if the speedometer reads OK or gets jumpy, indicating a bad cable
It only shows speed in one direction, but doesn't hurt it to spin it the other direction, thats happens when you back up, so if speedo doesn't show speed Reverse the drills direction

To replace speedometer cable you need a new cable, of course, and you will need to pull out the instrument cluster, to unclip it from the back of speedometer
Have 6 new Cluster back light bulbs, as this would be a good time to change them all, they are not expensive

If the gear is OK and the transmission still doesn’t shift properly, what next? I plan on draining/changing the fluid and filter while under there.

 

[RonD]

Fluid and filter would be the place to start

Examine pan, filter and fluid for any debris, metal flakes would be a bad sign, if you have a magnet run it around in the fluid and see if it picks up anything

Also check vacuum modulator(on passenger side) hose for ATF fluid

 

[scotts90ranger]

Would it be possible for the speedo drive gear on the transmission output shaft to loosen up without causing other issues on an A4LD? I know it's just a friction fit with the rear nut (if it's similar to a BW 1354 transfer case drive gear) but haven't been in an A4LD

 

[RonD]

Good question

No, on the 2WD automatics, the Drive gear on the tail shaft is machined on the shaft

Picture here: https://i.ytimg.com/vi/-Ej8u8nRBUA/maxresdefault.jpg

Thats an AOD transmission, but A4LD thru to the 5R55E 2WD have the gear there, just not used after 1998, so the nylon driven gear probably couldn't hurt the metal drive gear, and, of course, no slipping
I think the 5R55N and W shafts didn't have the drive gear

Yes, the transfer cases were different, they are not Ford specific so 6, 7 or 8 tooth drive gears could be installed, and yes they could slip if damaged

 

[scotts90ranger]

And now I know, thanks Ron!

To me it really sounds like a chewed up speedo gear.

I was going to mention that you need a 2 wheel drive speedo cable but then I got to thinking and can't remember if I changed that when I changed to 4x4 15 years ago... thinking harder I don't think I did... but then again maybe? dangit...

 

[Ranger101]

And now I know, thanks Ron!

To me it really sounds like a chewed up speedo gear.

I was going to mention that you need a 2 wheel drive speedo cable but then I got to thinking and can't remember if I changed that when I changed to 4x4 15 years ago... thinking harder I don't think I did... but then again maybe? dangit...

I took the VSS out and checked the plastic gear that is in the transmission. It’s in great shape.

 

[scotts90ranger]

There's a wire clip holding the speedo gear onto the VSS and I think something holding the VSS onto the end of the speedo cable, if the transmission is misbehaving there has to be something going on between the two. The speedo stopped is one thing, but the VSS is at the other end of the cable... did you try spinning the gear while you had it out? was there any resistance? There should have been a little...

 

[Ranger101]

There's a wire clip holding the speedo gear onto the VSS and I think something holding the VSS onto the end of the speedo cable, if the transmission is misbehaving there has to be something going on between the two. The speedo stopped is one thing, but the VSS is at the other end of the cable... did you try spinning the gear while you had it out? was there any resistance? There should have been a little...

I did spin the cable by hand, back and forth, and there was no resistance or binding. I attached a hand drill to it and it spun with no problem. Because I was by myself I couldn’t see the speedo while using the drill.

 

[RonD]

You need to see speedo when doing the drill test, so strap the drill up and tape the trigger on, then look at speedo for at least a minute

If its steady replace the combo unit in the transmission, you can reuse your Driven gear