Different Reason for Inaccurate Speedometer

benny3577

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Joined
Feb 4, 2019
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32
Location
Iowa
Over the last 7 years owning my TJ, I have fought getting the speedometer to read accurately even after swapping in what should have been the correct speedo gear after changing tire size. Most recently, I swapped new axles (4.10s) into the Jeep. I also installed the corresponding speedo gear based on the charts. This meant that I knew for sure my gear ratio, my tire size, and my speedo gear. Still, the speedometer was 10 mph off. I have been told that I must have been mistaken about one of these variables, otherwise the speed would read accurately.

In addition, my instrument cluster also indicated that I had higher than expected oil pressure (40 psi at idle, close to 80 psi at 2500 rpm). The speedometer needle also stuck at about 65 mph. It would not increase over that speed, and it took awhile for it to come down from that position when well under 65 mph.

I picked up a used gauge cluster for $20 today at a Jeep show. I wanted to see how it would act in my Jeep. Swapped it in. Now my speed reads correctly, and my oil pressure reads what I would think is more accurate (closer to 20 psi at idle).

See these pictures that were taken less than 30 seconds apart with the different gauge clusters.

IMG_6181.jpeg


IMG_6180.jpeg

**Ignore the airbag light, it’s removed in the cluster original to the Jeep as the airbags are disconnected.

Now, I will send the new to me cluster in to get reprogrammed with the correct mileage and we’ll be set.

I just wanted to throw this out there to anyone who is having a similar problem so that they know the instrument cluster itself could be the problem. I do not understand how these clusters can become inaccurate, maybe somebody else here does.
 
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Thanks for sharing this. It's always good to have these bits of info tucked away in the head somewhere.
 
Over the last 7 years owning my TJ, I have fought getting the speedometer to read accurately even after swapping in what should have been the correct speedo gear after changing tire size. Most recently, I swapped new axles (4.10s) into the Jeep. I also installed the corresponding speedo gear based on the charts. This meant that I knew for sure my gear ratio, my tire size, and my speedo gear. Still, the speedometer was 10 mph off. I have been told that I must have been mistaken about one of these variables, otherwise the speed would read accurately.

In addition, my instrument cluster also indicated that I had higher than expected oil pressure (40 psi at idle, close to 80 psi at 2500 rpm). The speedometer needle also stuck at about 65 mph. It would not increase over that speed, and it took awhile for it to come down from that position when well under 65 mph.

I picked up a used gauge cluster for $20 today at a Jeep show. I wanted to see how it would act in my Jeep. Swapped it in. Now my speed reads correctly, and my oil pressure reads what I would think is more accurate (closer to 20 psi at idle).

See these pictures that were taken less than 30 seconds apart with the different gauge clusters.

View attachment 458306

View attachment 458307
**Ignore the airbag light, it’s removed in the cluster original to the Jeep as the airbags are disconnected.

Now, I will send the new to me cluster in to get reprogrammed with the correct mileage and we’ll be set.

I just wanted to throw this out there to anyone who is having a similar problem so that they know the instrument cluster itself could be the problem. I do not understand how these clusters can become inaccurate, maybe somebody else here does.

Did you ever plug your original cluster back in to see if the issue changed after removing it?

I have an intermittent issue where the cluster goes dead and warning lights come on that seems most likely to be a connector issue. Whack the top of the dash and it all comes back. Never dug into the issue because now that its driven almost daily it doesn't happen.
 
Did you ever plug your original cluster back in to see if the issue changed after removing it?

I have an intermittent issue where the cluster goes dead and warning lights come on that seems most likely to be a connector issue. Whack the top of the dash and it all comes back. Never dug into the issue because now that its driven almost daily it doesn't happen.

My 99 did that until I pulled the cluster and gave each of the pins in the connectors a slight twist so they would sit more tightly in their sockets. Never happened again.
 
My 99 did that until I pulled the cluster and gave each of the pins in the connectors a slight twist so they would sit more tightly in their sockets. Never happened again.

There aren't many things I pick on the Jeep engineers for but I have big problems with how they designed the chassis side connectors for the cluster.
 
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There aren't many things I pick on the Jeep engineers for but I have big problems with how they designed the chassis side connectors for the cluster.

I didn't come to any conclusions but I have wondered why that seems to be an issue specific to those connectors and not every other connector in the harness.
 
Out of curiosity who reprograms the mileage?

-Mac

Do a search on google or eBay for “jeep tj reprogram gauge cluster” and you will find several people who will do it. It will cost me about $60 plus one-way shipping. They emphasize on the sites that this service is for matching your actual mileage on the Jeep. Artificially lowering your mileage is illegal if I understand correctly.
 
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Reactions: macleanflood
Did you ever plug your original cluster back in to see if the issue changed after removing it?

I have an intermittent issue where the cluster goes dead and warning lights come on that seems most likely to be a connector issue. Whack the top of the dash and it all comes back. Never dug into the issue because now that its driven almost daily it doesn't happen.

I have had both gauge clusters in and out of the Jeep several times. The original cluster has not corrected itself.
 
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Reactions: CMBD