strange behavior
Senior User
Joined: Sep 2006
Posts: 247
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From: NC
Can you actually feel the RPMs changing or is it just the RPM guage flucuating?
If you can actually feel it then it could be the speed sensor on the rear axle not giving correct info to the PCM, If it's only the RPM guage, then it could be the Cam Position Sensor as it controls the RPM guage.
I'm sure someone here will stear you in the right direction.
If you can actually feel it then it could be the speed sensor on the rear axle not giving correct info to the PCM, If it's only the RPM guage, then it could be the Cam Position Sensor as it controls the RPM guage.
I'm sure someone here will stear you in the right direction.
Postmaster
Joined: Nov 2005
Posts: 3,168
Likes: 10
From: San Ramon Ca.
Welcome to FTE!
The throttle position sensor comes to mind. Just guessing. The speed sensor on the rear axle is a possibility too I suppose. The torque converter could be randomly locking and unlocking. Since its free pull the sensor on the rear end and clean it up.
The throttle position sensor comes to mind. Just guessing. The speed sensor on the rear axle is a possibility too I suppose. The torque converter could be randomly locking and unlocking. Since its free pull the sensor on the rear end and clean it up.
Hotshot
Joined: Oct 2003
Posts: 17,791
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From: Ashland City, TN
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Senior User
Joined: Sep 2006
Posts: 247
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From: NC
If your running 60mph at 2000 rpm, then it has to be a 4.10 rear end and if the torque converter wasn't locked then you would be running around 2500 at 60. When the torque converter unlocks then the rpm's will go up. Yours are going down. The only way that you could be going 60mph at 1500 rpm is if you had something like a 3.55 rear end, then if the torque converter unlocked it would be feasible to see 2000 rpm and back and forth. The torque is pretty expensive to repair.
What rear end do you have in your truck? If it's a 4.10 or even a 3.73, then I don't think it would be the torque converter locking and unlocking.
One way to tell is while your driving take your left foot and barely touch your brake while staying on the gas with your right foot and see if the rpm's go up....if they do then your torque converter just unlocked and when you took your foot off the brake it locked back.
What rear end do you have in your truck? If it's a 4.10 or even a 3.73, then I don't think it would be the torque converter locking and unlocking.
One way to tell is while your driving take your left foot and barely touch your brake while staying on the gas with your right foot and see if the rpm's go up....if they do then your torque converter just unlocked and when you took your foot off the brake it locked back.
Postmaster
Joined: Nov 2005
Posts: 3,168
Likes: 10
From: San Ramon Ca.
You are still in the why stage. Keep it simple simple and check the cheap stuff first that might cause the issue. The torque locks and unlocks by command. If it were bad it would slip or just not function. Check your tranny fluid level too.
Postmaster
Joined: Sep 2007
Posts: 4,195
Likes: 6
From: Medford Oregon
Tried to Rep but must spread it around first.
Fleet Mechanic
Joined: Mar 2007
Posts: 1,808
Likes: 0
From: Meigs County Ohio
Just for information sake, are you talking about the switch that is used for the brake lights at the pedal? ANd are you saying that it is incorporated into the TC's electrical system and that it unlock the TC when your slowing down so a faulty switch would make it go in and out?