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Unread 09-15-2014, 05:13 PM   #1
Zyurazek
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Speedometer issue

So I'm having new speedometer issues. When I am going 70-80 mph, my speedometer thinks I'm going around 4mph. Then the shift light thinks I need to shift although I'm out of gears to move up to. Speedometer issue or computer? Also, a week before this started, I changed my clutch. Could a short do this? The odometer moves steadily.

95 YJ
5 speed 4.0L

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Unread 09-16-2014, 01:15 AM   #2
ThreeToe
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The shift light will always come on in the 1700 range in my 92, even 5th. I don't think that's related unless it's on the entire time. But I'm almost positive it runs solely of the rpm.
It sounds like your speed sensor might be pooched. It's the electronic sensor at the back of the Tcase. Take it out with a 13mm wrench and inspect the teeth on the gear. Then hook it up the speed sensor to a drill and see if it's reading speed when you turn the drill.

Last edited by ThreeToe; 09-16-2014 at 01:16 AM.. Reason: Spelling mistake
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Unread 09-16-2014, 01:18 AM   #3
ThreeToe
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Also take a mental note of the direction the speed sensor is clocked and reinstall it the same way. It can be installed 4 different ways based on the tooth count of the gear and won't work in 3 of the four positions.
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Unread 09-16-2014, 05:50 PM   #4
Gealii
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I'm not sure about the shift light being rpm dependent based on it coming on for me at different rpms in different gears.

As far as the speedo
check the speedometer gear, 2 bolts on the back of the transfer case with wires coming out, and inspect the gear for wear
the gear could be torn up or just barely making contact.

also check the motherboard behind the cluster for the speedo, it can be corroded and give false readings, just wipe the grime off
with rubbing alcohol, BUT DO NOT SCRATCH IT to get grime off or your speedo will not work at all
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Unread 09-16-2014, 06:16 PM   #5
fishadventure
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Engine load sensitive (vacuum) is how the shift light works I believe
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Unread 09-25-2014, 02:24 PM   #6
Zyurazek
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Well I've found the issue. I had once before bypassed the circuit board for the speedometer and a couple dash lights because of corrosion and my cheapness to find a new board. So u checked that the wiring was good. Next, I pulled the VSS. I pulled it and found the teeth a little chewed up. So I tried to spin it to see if the speedometer would work. It didn't. So then I pulled the gear out and found that the little shaft stripped out inside the gear and broke off. I had replaced the VSS before and the part was still under warranty. So 10 mins later I had a new part in my hand for free!

Even better news, while replacing the VSS, I also luckily had a spare gear on hand so I replaced it and it had fixed the second issue that has been stumping me. Whenever I would let off my clutch, the engine would bog down to about 300-400 rpms. A couple times the engine would stall out. My conclusion, the gear got stuck in the transfer case drive shaft which then would somehow put enough friction there to slow down my engine.

Can anyone tell me if that's possible? If not, I have no idea how I can tie in the other issue becoming fixed after I replaced the VSS.

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Unread 09-25-2014, 03:02 PM   #7
mike134
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My guess is that the speed gear would just be chewed to bits if it got stuck in the drive line, I don't think it could bog the engine down. The bogging may be unrelated to your speed sensor and either coincidentaly just started or you are just now noticing it because you are paying closer attention while diagnosing your speedometer problem.

Are all of your maintenance items up to date?
Spark plugs, wires, distributor, clean battery terminals
fuel filter
air filter

You should check for vacuum leaks by spraying carb cleaner on all of the vacuum lines while the engine is running, listen for a change in rpm.

You should check your fuel pressure with a fuel pressure gauge which you can borrow for free from autozone (just have to leave a deposit)

It could also be a clogged catalytic converter, but save that for last
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Unread 09-25-2014, 04:08 PM   #8
Zyurazek
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All general maintenance items have been done within the past 6-8 months (distributor, clutch, spark plugs,spark plug wires, starter, radiator, water pump, rear main oil seal, head gasket seal, I cleaned out all the gunk while inside the head,fuel filter, 50% of the fuel lines)...the list goes on. Cat was replaced along with muffler last December and I don't hear any sort of rattle. But like I said, this issue went away as soon as I fixed the speedometer.

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Unread 09-26-2014, 07:20 AM   #9
JeeperDon
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Quote:
Originally Posted by ThreeToe View Post
Also take a mental note of the direction the speed sensor is clocked and reinstall it the same way. It can be installed 4 different ways..
Three different ways. The 4th would be the same as the 2nd.
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