Speedo Problems

[87MJTIM]

My 87 4.0 is have problems with the speedometer.  I will be driving along and the needle will start to bounce.  Then it will drop to zero.  No movement. No mileage changing.  Nothing!

 

When I get back in to drive later, the needle will work for awhile.  I started using a GPS to track my speed.  When the needle is working, the speed matches the GPS.

 

Sometimes it will work for many miles, other times I cannot get out of my neighborhood before it stops.

 

The MJ has cruise.  Thus the speedo cables have two sections.

 

Steps done, both before and after the issue started:

 

1. Before the problems started, I swapped in a new speedo gear.  I found that my mileage was 5 mph lower than I was actually driving.  Changed from 31 to 29 tooth gear.

2. When it first happened, I checked all the cables.  I disconnected cables and spun them.  Both ends turned freely without any binding or looseness. 

3. Checked the cruise rev counter.  It turned freely, also.

4. Reconnected all cables and drove it around.  The needle worked at first, but after a few miles, it dropped to zero again.

5. Thought maybe the gear may be bad.  Swapped back in the 31 tooth.  Same problem.

6. Put back in the 29 tooth. Made sure that the number of teeth marking is at the 6 o'clock position when installing the gear holder.

7. Swapped out the speedo cluster with one I know worked.  Same problem.

8. Rechecked the speedo gear to make sure it wasn't spinning against the cable.  The gear held the cable tightly.

 

Help!

 

I've checked each end of the system and the parts in between.  I've swapped out parts that I know were working previously, yet I am still have the problem.  What haven't I considered?

[Marine1Texas]

when my 87 does it, I grease up the cable ends attached to transfer case and the back of speedo. It is cable and not electronic. So it does dry out for me. The other 2 things could be the gear in the transfer case on 4wd or in tranny is not spinning freely and is out of adjustment or gunked up. Or it could be something wrong in the speedo guage. I would try the lube first and see if that helps.

[87MJTIM]

Nori, thanks.

 

I will try greasing the cable ends.  

 

Previously, I did spray on some lithium lube on the speedo cogs.  It just gummed up the speedo causing it to read under and make noise.  I later sprayed on different lube to loosen up the old junk.  This was on the first speedo mentioned, not the second one I installed.  The lithium should not have affected the second speedo.

 

I also sprayed lithium into the cable.  But all it did was spray back at me.  I do not think it got down into the whole cable. Also, when I spin the cable, I cannot feel any resistance or binding.

 

You mentioned the drive gear in the tcase.  That is not something I messed with.  If I think this through, the gear would have to spin freely on the output shaft - thus not turning the speedo gear.  I guess I would have to pull the tail housing to inspect that.  Oh, joy.

[Eagle]

The problem started when you swapped the speedo gear. Did you properly "clock" the speedo quill that goes into the transfer case? The orientation is dependent on the number of teeth on the speedo gear. Not sure, but I don't think 6:00 o'clock ids the index location.

[HOrnbrod]

37 minutes ago, Eagle said:

The problem started when you swapped the speedo gear. Did you properly "clock" the speedo quill that goes into the transfer case? The orientation is dependent on the number of teeth on the speedo gear. Not sure, but I don't think 6:00 o'clock ids the index location.

 

The two speedo gears the OP used were 29T and 31T. Both of these speedo gears use the same "clocking"; both set in the 26T-31T position. Pretty hard to screw it up.......

[87MJTIM]

I did clock it with the gear teeth range at 6.  I thought I saw that on youtube.

 

I will double check the orientation.

[Eagle]

According to the 2000 XJ FSM, 6:00 o'clock is the correct index. I would pull it anyway, and inspect the speedo gear for possible damage.

 

Is the new gear the same length as the original?

[87MJTIM]

Yes, it is the same length.  In fact, I took the speedo out of an older tcase (21 spline) that used to be on the truck.