Transmission Input Shaft Speed Sensor, Output Shaft Speed Sensor

CaRJoE0220 · 12-21-2007, 03:27 PM

I have noticed there are times that if I take of normally in my 99 Grand Cherokee (4.0L Auto) That the revs will slowly creep up and out of no where it just revs higher then normal for a second then switches gears.

At first I thought the worst of the tranny may have been slipping but I dont really think thats the issue because it only happens when i take off and slowly go up to 35-40mph. I went online to see what I could find.

MSN Auto rated the tranny as having problems (along with almost the whole rest of the vehicle haha) but specifically stated this

Quote:

Occasional problems on this vehicle are failure of the Transmission Input Shaft Speed Sensor, 5 speed automatic transmission only, and the Output Shaft Speed Sensor. The cost to replace either the Transmission Speed Sensor or the Output Shaft Speed Sensor is estimated at $25.60 for parts and $32.50 for labor. All prices are estimates based on $65 per flat rate hour and do not include diagnostic time or any applicable sales tax.

Has anyone had this issue and was this what went wrong. I dont know if this could be my issue but if anyone has had experience with this before that would be awesome.

Thanks Guys

Turbonut · 12-21-2007, 04:35 PM

http://www.wjjeeps.com/speed_sensors.htm

The 45 and 545 have 2 speed sensors, while the 42 has only one.
When the sesors go, I believe there is a display code and trans does not shift. Never encountered a problem, but quite a few on the site have if you want to search.

Kheeney5 · 04-05-2010, 06:07 PM

I had a speed sensor go out and my Check engine light came on, along with my transmission having weird shifts.

nkerns · 05-31-2011, 09:45 PM

I have a 2008 Grand Cherokee and just took it to the dealership today because the check engine light came on and it was having problems shifting. The top speed was 40 mph. After we shut the engine off and started back up it was fine. The dealership hooked it up and got a code for the transmission but they don't think that's what it is. A friend suggested it was a senor. The dealership is saying they don't know for sure what is wrong be probably going to cost $800. Any suggestions would be greatly appreciated.

**99JGCWJ** · 06-01-2011, 05:05 AM

When mine went I was on the parkway. The Jeep started grinding gears in D and it didn't like going over 40 mph. I pulled off the parkway drove home in 2nd without it grinding. Got home, shut it off and let it cool down. An hour later I drove it around the block in D and it drove fine. The next day it didn't want to shift out of 2nd gear. I went to the dealer, bought the sensor for I think $30.00 and changed it out. It took all of 10 min and solved the problem.

CanadianZed-J · 06-01-2011, 07:38 AM

Quote:

Originally Posted by 99JGCWJ

...I went to the dealer, bought the sensor for I think $30.00 and changed it out. It took all of 10 min and solved the problem.

For next time, it's really easy to test these sensors. Put an ohm-meter on the two contacts then hover it back and forth over a fairly powerful magnet. If the sensor is working you should see the resistance fluctuate as it passes the magnet.

BTW, old thread! (except for the new guy's problem).

CZJ.

metalhead · 06-01-2011, 07:58 PM

My output speed sensor went bad on my 2000. The tranny would feel like it was slamming into second and then it would not shift any higher. I did get a code. Of course the mechanic I took it to replaced the input speed sensor instead of the output sensor even after I gave him the part and told him where it was.

nkerns · 06-01-2011, 08:26 PM

I got the code from the dealership (next time I will go to an auto store and get it for free) and it was PO717-input speed sensor. I ordered the part and I'm going to change it tomorrow. I've never worked on a car before- I'm a girl. And I've done my research and even found a thread that has pictures on how to change it but my Jeep is a 2008 and I read it might be on the passenger side for that year. Any help would be great. My friends (who are also girls) don't think I can do this and I want to prove them wrong! Thanks!

CarlJH · 06-01-2011, 08:36 PM

If you have the new one already just get under the car and find the same thing on the tranny. When you take the old one off just double check its the right part then just put the new one in. You might need to disconnect the battery for a while so the tranny forgets its settings so it can learn them again with the new sensor

nkerns · 06-01-2011, 08:42 PM

Thanks! The new part will be in tomorrow so I'm sure once I see it I'll be able to fine where it is. The other threads made it sound like you didn't have to get under the car. Do you just mean under the hood?