Urgent: Transmission Speed Sensor Error, Stuck in 2nd Gear - Jeep Garage - Jeep Forum

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  #1  
Old 09-01-2016, 04:02 PM
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Unhappy Urgent: Transmission Speed Sensor Error, Stuck in 2nd Gear

I own a 2005 Jeep GC Laredo 3.7L v6 45RFE transmission 170,000 miles. I'm from Mass and drove down to New Jersey last weekend with no problem. The next day I was driving about 30 mph on a side road and my engine starting revving up like it was in neutral reaching 2500-3500 rpm and was stuck in second gear. The +/- option to shift gears/ overdrive on the stick shift also stopped working completely. The normal jeep "clunk" sound when shifting from park to drive or vice versa was noticeably louder and heavy. I had the memory card read at AutoZone (because it was a Sunday and no one else was open) and it was a p0717 issue. I know that has to do with the input speed sensor sending no signal to tell the transmission when to shift gears. Check Engine light also came on. I tried restarting the car, giving it an hour to rest and driving it again, same thing. So I figured I would take it to a transmission specialist. He let the car sit for a day or two then looked at it and drove it and couldn't recreate the issue. He said nothing out of the ordinary happened for him, but 2 days before that I couldn't drive over 30 mph without the engine going crazy and no shifting occurring. He said its possibly a wiring issue that is intermittently cutting off the sensor signal, or it could be a problem with the actual sensor but he has no way of telling unless the issue can be recreated. I'm weary that its a total circuit or computer issue.

I have seen other posts from people with somewhat similar sensor error issues but not close enough to be able to derive an answer. I know jeep had a transmission recall back in 05 that had to do with fluid leaking and sometimes destroying the tranny but I don't think that the recall has to do with the problem and the dealer that performed the work for the recall for the previous owner is out of business. Meanwhile I had to go back to Mass to make work and my car is still in Jersey so I can't be down there. The mechanic said if he can't recreate the issue that I have three options: Replace the sensor, hope that this was in fact the issue and it fixes the problem. Take it to either a dealer or an electrical specialist to see if the computer or wiring is the culprit, or just drive it off the lot and hope it was a one time anomaly. This is stressful because I'm not physically in the same state as the car and have to conduct this process over the phone. On a side note, the day this started happening the AC worked fine but was making a weird low almost farting or whirring type noise and the bottom of the car had intense fluid leaking from it when the AC was turned on. I will also say that the car had been driven a lot and it was incredibly hot out in this 4 or 5 day stretch. Any help, advise, or comments are greatly appreciated because I'm lost.

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Old 09-02-2016, 12:07 AM
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Re: Urgent: Transmission Speed Sensor Error, Stuck in 2nd Gear

We see input and output speed sensors issues quite a bit on the NAG1 transmission (by the way you have a nag1 trans not a 45rfe if you have a V6), normally we replace the transmission lead frame that has both of the speed sensors attached, it requires the valve body to be removed so it is kinda of involved.
Also your normal jeep clunk from park to reverse ect. is not normal it means your front axle mount bushing is probably totally torn through and letting your front axle slam up and down when you shift
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Old 09-02-2016, 11:40 AM
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Re: Urgent: Transmission Speed Sensor Error, Stuck in 2nd Gear

I wasn't sure of the type of transmission I had, I used cars.com for specs and I must have selected another car by mistake. The problem is this mechanic is telling me the speed sensor is fine as of today. I left out one detail that I didn't mention because I didn't think it had anything to do with my transmission situation. About half way down on my drive to NJ my dashboard lit up saying "check gas cap" When I got down to Jersey I stopped and checked and the bottom part of my gas gap was broken possibly causing air to breach the fuel tank.

I did some research on another thread and someone with a 99 Dodge Dakota (Chrysler makes the computers for Jeep and Dodge) posted about the speed sensor being faulty and being stuck in second gear when he is critically low on fuel. An engineer saw the post and responded that Chrysler car computers are notorious for going into "limp or safe mode" when there is air in the fuel tank because the transmission sensors base their calculations on pressure and when you're running the car and burning gas combined with either a broken gas cap or really low fuel the transmission can lock itself out because it doesn't know the correct speed of the car based on the given amount of pressure.

I'm wondering if (since I drove all the way to NJ, about 270 miles, with a broken gas cap) my tranny locked itself out because of it. It sort of makes sense because I bought a new gas cap the same day, and my car sat for 2 days after not running and then restarted and according to the mechanic is now running normally. Is it possible that from sitting for 2 days with a working gas cap that the fuel tank was able to depress the air that was in it, and thereby unlock the transmission for normal shifting?

I know most speed sensor issues do result in valve body work but if the car is running fine is what I'm thinking possible?

Thank you for the reply.
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Old 09-10-2016, 11:00 AM
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Re: Urgent: Transmission Speed Sensor Error, Stuck in 2nd Gear

We just went through this. I have an 07 with the 545rfe and my roomate has an 05 just like yours. NAG1. Speed sensors on all four wheels. it resolved the issue and also ran much more smooth than before. Start there. If that doesnt do it go ahead and change the sensor in the transmission. Total time for the entire fix was about 2.5 hours. When doing the wheel speed sensors get some pb blaster or if you have access to it "open and shut" from diamond. We literally just went through this a few weeks back. 99% this should be the fix.Check between rockauto.com and amazon. Great prices.
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