No Idea what so ever
06-28-10, 08:13 PM
#1
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No Idea what so ever
Hey everyone, I have no idea what could possibly be going on. This has been happening for the past 2 years since I bought the car. Here is the scoop.
Car is driving fine, smoothly, goes perfect down the road. Upon the ~40mph range the SC400 auto tranny shifts into OD. This would be all fine and usual which it is, however if you try to give it moderate gas (enough to NOT downshift but accelerate in OD) The engine flails ALL over the place and the car shakes and it feels like the engine is going to fall out of the car. How do you resolve this? Give it more gas and make it downshift, then its perfect. OR, just let off the gas a bit and accelerate a little slower. OR, you can just wait out the craziness of the shaking engine until I reach ~50mph + then it doesn't do it at all. It will be FINE from ~35mph but as soon as you hit 40mph the engine does its flailing thing then goes away as soon as you leave the 40mph region.
What the f*** is going on here?
Car is driving fine, smoothly, goes perfect down the road. Upon the ~40mph range the SC400 auto tranny shifts into OD. This would be all fine and usual which it is, however if you try to give it moderate gas (enough to NOT downshift but accelerate in OD) The engine flails ALL over the place and the car shakes and it feels like the engine is going to fall out of the car. How do you resolve this? Give it more gas and make it downshift, then its perfect. OR, just let off the gas a bit and accelerate a little slower. OR, you can just wait out the craziness of the shaking engine until I reach ~50mph + then it doesn't do it at all. It will be FINE from ~35mph but as soon as you hit 40mph the engine does its flailing thing then goes away as soon as you leave the 40mph region.
What the f*** is going on here?
06-28-10, 08:53 PM
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Well first, it sounds like the engine is lugging, (What are the rpms in an sc400 at 40mph in OD anyway?) but I'm wondering what condition your motor mounts are in to cause so much vibration when lugging.
06-29-10, 09:19 AM
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Ah, good suggestion! I did not think of that at all. My SC is at about 1200 RPM in overdrive at 40mph. Can motor mounts be tested if they are bad or not? This actually seems plausible.
06-29-10, 10:11 AM
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To be honest, I'm not too familiar with the 1UZ mounts, but in general, I've been able to find bad mounts by watching the block while having someone put the car in gear and rev it while hold the brakes hard. If the blocks jumps or torques severely out of position, you probably need mounts. You can also just pry the block with a long lever and see how much it moves around. G/L
06-30-10, 09:33 AM
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it's not your spark plugs and it's not your motor mounts. I have read about this problem before and my car does it too. If I recall correctly, it has to do with the tourque converter and the locking/unlocking of the TQ at 40mph. I'll do some digging and see what I come up with.
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06-30-10, 08:39 PM
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it's not your spark plugs and it's not your motor mounts. I have read about this problem before and my car does it too. If I recall correctly, it has to do with the tourque converter and the locking/unlocking of the TQ at 40mph. I'll do some digging and see what I come up with.
06-30-10, 10:00 PM
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So basically what I have been reading has two possible solutions...Complete tranny flush with Type IV fluid or replacing the TQ Converter. There was one person who replaced it with a Dragon TQC but the problem remained...weird. Do a search on the 40 mph shudder and read what I have been reading. Lex Luthor had a very long thread on the issue too.
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