2002 TJ Speedometer issue after SYE install - Jeep Wrangler Forum
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Old 08-10-2013, 04:04 PM   #1
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2002 TJ Speedometer issue after SYE install

I have a 2002 TJ Sahara with 33” tires and stock 3.73 gears. I purchased a JB Conversions Super Short SYE and had it installed (didn’t feel up to working on the innards of the transfer case in my sandy barn) by a local drivetrain shop that has installed, according to them, hundreds of these without issue. The shop came highly recommended by 2 separate sources independently so I feel confident in their ability. The problem I am having is with the speedometer – it is reading WAY too high.

After they completed the installation they called and asked if I had any issues with the speedometer previously and I told them I had not. They said the mechanicals of the install were fine but when they test drove the Jeep the speedometer would go over 100mph in second gear. They also mentioned that the Jeep would stall if they took off too aggressively (like when you pull onto a busy road). They had taken it apart and rechecked the installation of the tone ring and also verified the torque was set correctly and were trying to get ahold of JB Conversions. I did some research that night and found many posts about the torque issue, and a few posts by people that had found the speed sensor was bad, and a single post where the factory wiring had a short. As the shop had already checked the torque settings twice I focused on the sensor and wiring. The poster with the bad wiring said they had the problem even when the speed sensor was disconnected. I talked with the shop the next day and suggested that if they unplugged the speed sensor and all the other symptoms went away it may help to verify the speed sensor as the cause. They did and took it for a test drive and the issue went away (other than no speedometer obviously). I managed to get ahold of JB Conversions myself that night and they sent a new speed sensor.

It arrived yesterday and the shop didn’t have time to install it so I brought it home and installed it today (I didn’t want to wait until Monday to find out if the problem was fixed). I took the Jeep for a test drive up and down my driveway at >100mph and put 2 miles on the odometer – problem not solved. The speedometer seemed to move smoothly – it’s almost as if there is a calibration issue. I didn’t drive far (my driveway is about 300ft) but did try to give it some hard accelerations and I did not get any stalling issues.

More info - when I drove the Jeep home yesterday I noted the check engine light was on – probably because the speedometer isn’t working. And one time I noticed the shift light was on while I was in 5th gear cruising at about 55mph (using gps) and roughly 1800RPMs – again I am guessing the speedometer caused this but I thought it was odd that it would tell me to shift if I was in 5th gear and as far as the Jeep computer was concerned, I wasn’t moving. The Jeep did stall on me twice on this drive – once when I had made a slow right hand turn and once as I was slowing down (coasting at <20mph) just before my home. Both times the Jeep started up immediately without issue and there were many other slow speed turns without issue between the two events. The Jeep has no history of stalling prior to this.

Does anyone have any ideas on what to try next? The shop told me to bring it back Monday if the problem wasn’t solved as they have another theory – but I don’t know what their theory is and if it doesn’t work, I’d like to have some suggestions on what to try next.

One last tid-bit of information that may or may not be important – I installed a UCF No Body –Lift Needed Transfer Case skid just before getting the SYE installed. Prior to this I had an approximately 1.5” drop on the T-case skid to take out driveline vibrations incurred when I installed my lift 11 years ago (things slowed down when the kids came along). I drove the Jeep to the shop in 4-Hi with the rear driveshaft removed and did not notice any anomalies with the speedometer during that 30 mile trip (drove to work first) so I don’t think this played a part, but I’m not certain.

OK, sorry for the book and thanks in advance for the help.

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Old 08-10-2013, 07:38 PM   #2
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What size tires and what is your differential gearing? The electronics are set up for a stock application and there is no speedo gear in the JB SS SYE, just a sensor and a tone ring. My guess is that you'll have to correct your speedometer with an electronic recalibration device. There are a few on the market, but I don't recall all their names. I used the SpeedoHealer from Blue Monkey Motor Sports on mine when I installed my JB SYE, and it works well. Blue Monkey Motorsports, Inc. : : : : HealTech Electronics SpeedoHealer (R): Product Overview Plug and play, and easy to program. As far as the shift light on the dash, it merely goes by rpms, and on mine it's on going down the freeway in fifth gear wanting me to shift agin into a higher gear I don't have.

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Old 08-11-2013, 09:13 PM   #3
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The tire size is 33” (32.5” actually) and the gear ratio is 3.73. The speedometer was off some before the install due to the larger than stock tires –but the stock tires were 30” so it was only about 10% and it was reading lower than actual not higher as it is now. Thanks for the link though, I had started to research how I would modify the speedometer and that looks like an extremely easy to install unit. I can honestly say I don’t remember my Jeep ever telling me to shift when I was in 5th gear, 4th gear at 1400rpms – yes, but it seemed to understand that I didn’t have a 6th gear.

It was suggested to me to try pulling the connection from the negative side of the battery to see if resetting the computer may help. I pulled it for 15-20 minutes, plugged the sensor back in, reconnected the battery (it was disconnected long enough to reset the trip odometer), started it up and took it for a test drive. It is still WAY off. I had my phone GPS running and when the GPS said 3mph – the Jeep speedometer read 40mph, when the GPS said 6mph – the Jeep said 70mph, at GPS 7-8mph the Jeep was reading 100mph. The speedometer wasn’t “jerky” but it was difficult to maintain a steady reading due to the fact that the speedometer seems to be off by a factor of almost 10x. I just don’t understand why my Jeep would have this calibration issue when many other Jeep owners have installed this JB Conversions kit and not had the issue.

Any more thoughts out there?
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Old 08-16-2013, 01:04 PM   #4
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UPDATE SOLVED:
Monday I spoke with JB Conversions again and he told me they have a 40 tooth tone ring for GM applications that may have been in my kit by mistake. At that point I was extremely hopeful the situation was solved because it fit so well – 40 tooth tone ring vs 3 tooth tone ring and 40mph speedometer reading vs 3mph GPS reading.

The replacement tone ring showed up on Wednesday and was installed yesterday. I drove the Jeep home and the speedometer worked as it did before (about 10% off due to the larger than stock tires). I also didn’t experience any stalling on this trip. I’m not sure why the speed sensor not working would cause the stalling issue but I’m hoping it was so I don’t have to trouble shoot that problem any further. And the shift light didn’t come on once while in 5th gear.

This situation probably won’t occur for anyone else but it does go to show that you should check the parts you purchase closely even (especially?) if you aren’t installing them yourself. Also, as has been said out here many times, it is better to buy the parts through the shop that will be installing them so they will be responsible for any troubleshooting should it be necessary. It only cost me an extra $40 for the troubleshooting labor (they took it apart several times before we found it was the tone ring and I didn’t get charged for that) so I am not complaining too loudly but had it been their purchase they would have been asking JB for the money not me. So lesson learned (I had actually bought the SYE kit prior to joining this forum and for whatever reason never even considered to buy the kit through the shop that I would have install it).
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Old 08-16-2013, 03:44 PM   #5
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Dont have a SYE yet.

I put 32 inch MTRs on my 02 Sport. it had 31 firestones when i got it. before the new tires the speedo was 7 mph low, with the newtires it was 10 low just put 4.11s in to correct the driveing with taller tires but now the speedo is running 10 mph higher. Using my GPS until i can get the SYE then will worry about correcting the speedo.
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speedometer , sye install , troubleshooting

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