overdrive vibration?????
Grand Champion
Joined: Aug 2009
Posts: 5,971
Likes: 45
From: MAINE
Uhh, your trans actually works harder in overdrive then it does in normal gears. that's why they tell you to switch it off when you tow.
Just because the engine RPM's are lower doesn't mean the trans isn't doing more work.
The engine RPM's get reduced to a ratio of 0.69:1 in OD because the trans does the extra work to make the truck maintain the same speed at a lower engine RPM. If your engine's running 2000 rpms in OD, your trans is running like it would at about 2900 RPMs in 3rd gear at a 1:1 ratio. At 2500 engine RPMs, your trans is outputing about 3623 RPM's worth of work. The driveshaft spins faster too.
The only part of the drivetrain that gets a break in OD is your engine.
A bad snap ring can cause poor or no OD engagement, an unbalanced driveshaft can cause a type of "harmonic wobble" at certain RPM's. If the OP drives his truck conservatively, he may not ever reach that specific driveshaft RPM range until he gets into OD.
If might also be a failing OD solenoid or sensor. It also could be the TC as the OP suspects. Could be a lot of things including the suspension, but the OP hasn't reposted.
Just because the engine RPM's are lower doesn't mean the trans isn't doing more work.
The engine RPM's get reduced to a ratio of 0.69:1 in OD because the trans does the extra work to make the truck maintain the same speed at a lower engine RPM. If your engine's running 2000 rpms in OD, your trans is running like it would at about 2900 RPMs in 3rd gear at a 1:1 ratio. At 2500 engine RPMs, your trans is outputing about 3623 RPM's worth of work. The driveshaft spins faster too.
The only part of the drivetrain that gets a break in OD is your engine.
A bad snap ring can cause poor or no OD engagement, an unbalanced driveshaft can cause a type of "harmonic wobble" at certain RPM's. If the OP drives his truck conservatively, he may not ever reach that specific driveshaft RPM range until he gets into OD.
If might also be a failing OD solenoid or sensor. It also could be the TC as the OP suspects. Could be a lot of things including the suspension, but the OP hasn't reposted.
good to know...
Thread Starter
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Registered User
Joined: Dec 2009
Posts: 7
Likes: 2
it will not shake in any other gear. if im in 3rd gear goin 60, its smooth, then when i press the overdrive button and it shifts in, then it starts shaking. ive been a mechanic for years and i know its not a tire issue or a driveshaft issue. i was just wondering if this is a common problem so it could help my diag.
Registered User
Joined: Jan 2010
Posts: 1
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From: O-H-I-O
Hello 2nd Geners. First pot here. I stumbled upon this forum trying to track down this exact problem.
I have the exact same symptoms as the OP. It happens only in O/D. I gets noticeably worse the faster I go especially past 60mph. I am leaning towards the torque converter as well. I'm going to crack the pan tomorrow and have a look. I just can't see it being a u-joint or driveshaft balance. I think that would be somewhat noticeable in any gear at any speed.
I have the exact same symptoms as the OP. It happens only in O/D. I gets noticeably worse the faster I go especially past 60mph. I am leaning towards the torque converter as well. I'm going to crack the pan tomorrow and have a look. I just can't see it being a u-joint or driveshaft balance. I think that would be somewhat noticeable in any gear at any speed.
Thread Starter
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Registered User
Joined: Dec 2009
Posts: 7
Likes: 2
just got it back from the local dodge dealer and they found that its a misfire causing the vibration. they checked compression and found low compression in all but 1 cylinder. i pulled the heads off and found one head chamber had leaked down after i poured tranny into them. the head gaskets have signs of blow by. im hoping the one that leaked down isnt a cracked head and just needs valves. any input with suggestions??
Professional
Joined: Mar 2021
Posts: 190
Likes: 1
just got it back from the local dodge dealer and they found that its a misfire causing the vibration. They checked compression and found low compression in all but 1 cylinder. I pulled the heads off and found one head chamber had leaked down after i poured tranny into them. The head gaskets have signs of blow by. Im hoping the one that leaked down isnt a cracked head and just needs valves. Any input with suggestions??
