Another Speedometer problem

[trex-x-xj]

O K Let me start by saying I have searched but have not found the info I need.

I have the bouncing speedo from what Ive read a severe case (at 50mph? it bounces from 0-35-0-85-0 and so on) like some kind of gag gauges haha .
I have checked everything out and it is all in good shape (used a drill in reverse on the xfer case side of the cable and the speedo operated fine)
BTW.. the vehicle speed sensor checked out as well.
I have narrowed it down to the drive gear in the transfer case. How difficult is it to access. Are there any good writeups on the repair? As common as this seems there isnt much info.

I know it is only a speedometer but I think the signal the speed sensor is sending will not let my Overdrive function properly. I will be driving the Ex at least 100 miles a day 5-6 days/wk so mileage is a concern.

Thanks for any help

 

[mikeinri]

"I know it is only a speedometer but I think the signal the speed sensor is sending will not let my Overdrive function properly."

At the risk of being completely wrong about this, I really don't think your concern is warranted. I believe that the A4LD is completely mechanical (vaccuum controlled, etc.), not electronically controlled, so your speedometer not working should have no impact on whether or not the overdrive works correctly.

Mike

 

[JDraper]

Speedometer on your '92 has nothing to do with the overdrive functionality.

I know you checked the cable, but I'd still suspect it. When you test it with a drill, it doesn't sit at the same angle, or have the same bends in it as when it's installed.

To get to the gear in the Xfer case, you're probably going to have to remove the case and open it up. It's not a serviceable part with the xfer case installed.

 

[CRUISERMEDIC]

im not sure where the gear is on your year. i had the spedo drive gear go bad in mine to. i took of my rear drive shaft and took apart the output flnge thingy and it was right there. very easy to do. hardest part was finding the replacement gears. ford says mine was discontinued took some searching around. remember i think there are right hand gears and left hand ones to make sure you get the right one for yours

 

[trex-x-xj]

There is no direct connection with the speedometer to the tranny? Then what is the Vehicle Speed Sensor for? Ive read in a post somewhere on here that the VSS

does the transmission shift into overdrive? if not, you probably have a problem with the speed sensor. i had that problem with mine.

Thats just one quote I found real quick. I can see the VSS for the cruise control but comments like this make me think it also helps controle the shifting into overdrive. I just spent 2000$ on a AAA rebuild and I do beleive there are electric shift solenoids that the computer manages.

I dont mean to be cruel but how long have yall had your X's. I havent really done much with mine. had the tranny rebuilt about a 16 months ago, and let it sit till I could save up enough for a motor. I'm driving it now with the problems just so I can make some needed repairs to my Jeep Cherokee.

Thanks Medic I'll continue to try to look for some diagrahms and parts before diving in and leaving with nothing to drive to work!

 

[JDraper]

On a '92, the speedo is mechanically driven. It's totally independent of any sensors, so your speedo bouncing will have zero effect on the tranny. There is a VSS, but IIRC it's only used for the cruise control in the '92 Explorer.

BTW, I'm moving this to the transmission forum so you get better visibility with the tranny experts.

 

[Glacier991]

You can access the vss drive gear in the 1354 in vehicle by dropping the driveshaft, removing the flange, and then popping out the oil seal. It will be right there.

And I respectfully disagree with whomever suggested the A4LD is all mechanical. The Explorer version used two solenoids, one to command lockup in the torque converter. (ALL A4LD's had this, in fact the LD means locking device). The other is for the 3/4 shift and the PCM commands this shift, and part of the input for the computer to command it is the VSS. (early versions of the A4LD did not have this... but by the time the Explorer came around the A4LD has this feature so they all do... 91-94 1st gens anyway.

A bad VSS will cause a lack of OD.

All this said, before I'd suspect a trapped spiral gear arrangement (which is what drives the VSS output), I'd be wondering about the VSS sensor itself.

 

[quasarsky]

hey glacier, will a bad vss in a 98 ford explorer cause a lack of OD? thats what the guys at autozone told me, for the check engine code i had. they said the speed sensor in the tranny needed to be replaced.

 

[trex-x-xj]

Cool Im glad to hear the drive gear is that easily replaced
I did check the VSS and it read good. Now to find a gear.
Thanks Glacier for the info ...
Thanks for moving the post J D (Im still a nooB in forums)

 

[mikeinri]

Thanks for correcting me glacier. I knew there were sensors, but didn't realize there were control inputs. I thought all the solenoids were simply vaccuum/fluid controlled. That's why I love this site, learn something every day...

Trex, I've had my 94 since 1999. I've put over 210,000 miles on it since then, it has 264,000 total, all with the original 4.0 OHV and A4LD. Doesn't make me an expert by any means, I was just trying to help.

I can tell you that I have a bouncing speedo, but it has NEVER affected the overdrive OR cruise control, so I've been ignoring it for a few years. It really only happens at highway speeds in my case, and bounces above my true speed, not below.

Wait a minute... "I have a bouncing speedo..." Now THERE'S a visual we can all do without!

Good luck, keep us posted.

Mike