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.