Tranny/OD thud, jolt, jump issue

[betz]

Okay, I did some searching and found a number of threads regarding this issue, but none of them were conclusive. I know very little about the workings of an Auto Tranny, so maybe someone could guide me to a good conclusion. Here are the conditions and the issue:
Engine must be all warmed up. After driving 55-60MPH for 10-15 seconds, I let off the gas until I hit 45MPH. Then I push on the pedal just enough so that the car is being fed gas, but it is actually decelerating (which means I am running approx 1500-1700 RPMs). As it decelerates from 45-35MPH I get an occasional jolt/thud. It's like my car is being bumped or pulled forward really hard and really short. I usually get 2-3 of these thuds in a row. Just like that: thud, thud, thud. It's almost like going through three big potholes. It definitely feels like it comes from the tranny. If I let off the gas completely or give it some gas, the thuds immediately disappear. Sometimes this thud is much more noticeable than others. The conditions I described above seem to give me the most emphatic results. Anyhow, i decided to replicate these conditions, but with the O/D disabled(off). Obviously the RPMs don't match up with the speeds when O/D is disabled, so I replicated the conditions according to speed and then according to RPM. I was not able to reach the same results. SO, I tend to think that there is a problem with the overdrive, and that it just doesn't want to disengage and downshift a gear, so instead, it kind of disengages for a second, but then immediately re-engages. What are your thoughts?

For a little Hx, my car is a '96 Camry LE v6 1mz w/automatic transmission. She now has 160,000miles. The first time I noticed this little jump was a little over one year ago. I didn't really notice it too much until the last few months. I changed my tranny fluid, filter, and gasket about 3 weeks ago to try and make things better.

Also, based on the info I have given, I came up with a few questions:
Is there a way to have just the overdrive fixed without doing a full tranny re-build?
Will using high-mileage fluid/synthetic fluid/additives help? If so, which ones and which brands?
Is it a good idea to just disengage the O/D until I need it for the highway/freeway?
Would dropping the pan and cleaning out the tranny valve body help? (actually, I don't know what the trans. valve body is or how to clean it, but another guy mentioned it).
Is the current condition bad for my car/going to cause the tranny to blow up?

Thanks for your help,
-Mike

[wahed3001]

Originally Posted by betz

Okay, I did some searching and found a number of threads regarding this issue, but none of them were conclusive. I know very little about the workings of an Auto Tranny, so maybe someone could guide me to a good conclusion. Here are the conditions and the issue:
Engine must be all warmed up. After driving 55-60MPH for 10-15 seconds, I let off the gas until I hit 45MPH. Then I push on the pedal just enough so that the car is being fed gas, but it is actually decelerating (which means I am running approx 1500-1700 RPMs). As it decelerates from 45-35MPH I get an occasional jolt/thud. It's like my car is being bumped or pulled forward really hard and really short. I usually get 2-3 of these thuds in a row. Just like that: thud, thud, thud. It's almost like going through three big potholes. It definitely feels like it comes from the tranny. If I let off the gas completely or give it some gas, the thuds immediately disappear. Sometimes this thud is much more noticeable than others. The conditions I described above seem to give me the most emphatic results. Anyhow, i decided to replicate these conditions, but with the O/D disabled(off). Obviously the RPMs don't match up with the speeds when O/D is disabled, so I replicated the conditions according to speed and then according to RPM. I was not able to reach the same results. SO, I tend to think that there is a problem with the overdrive, and that it just doesn't want to disengage and downshift a gear, so instead, it kind of disengages for a second, but then immediately re-engages. What are your thoughts?

For a little Hx, my car is a '96 Camry LE v6 1mz w/automatic transmission. She now has 160,000miles. The first time I noticed this little jump was a little over one year ago. I didn't really notice it too much until the last few months. I changed my tranny fluid, filter, and gasket about 3 weeks ago to try and make things better.

Also, based on the info I have given, I came up with a few questions:
Is there a way to have just the overdrive fixed without doing a full tranny re-build?
Will using high-mileage fluid/synthetic fluid/additives help? If so, which ones and which brands?
Is it a good idea to just disengage the O/D until I need it for the highway/freeway?
Would dropping the pan and cleaning out the tranny valve body help? (actually, I don't know what the trans. valve body is or how to clean it, but another guy mentioned it).
Is the current condition bad for my car/going to cause the tranny to blow up?

Thanks for your help,
-Mike

Did the symptoms get better or worse after the fluid and filter change? I hope you used the right kind of fluid and also made sure it wasn't over-filled.

[betz]

Well, the symptoms are still the same after the fluid change. Yes, the fluid is overfilled a bit. I used the right type of fluid (Mercon III), but like I said the problem existed before the fluid change. I want to empty the fluid that's in there and replace it with something better if possible, which is why I asked about using synthetics or high-mileage fluids.

[betz]

After some more driving, I realized that my car also does this when overdrive is off at about 40mph/2000RPM. However, it isn't anywhere near as sever as when the O/D is on. This makes me think that maybe this is a TCC issue? Ideas?

[Quicksilver300]

I dont know if this is the same issue, but my car thuds into and out of OD. If I'm on the throttle pretty hard it doesnt seem to do it, but if it's a low stress shift into OD, it thuds.

[Kep]

Check your engine mounts. I would be especially suspicious of the "dog bone" one on the top passenger side of the engine.

Kep