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Hi All,

I have been going crazy, literally for over a year trying to diagnose a rattle from under the car when accelerating lightly through about 40 mph. (4 cyl Limited, 168k miles) I have read countless suggestions about heat shields, etc. One wonderful soul, who i can't identify any more, because I've looked at so many threads, said it might be a torque converter problem and that when he changed the transmission fluid, the rattle disappeared. He was kind of apologetic because the solution was so far-fetched. I have always been skeptical of tranny fluid changes, thinking they were mostly extra profit for the quick-lube places. But I was desperate, and decided to try it. Guess what? It worked. Don't ask me why or how, but it worked, in a matter of a few hours. So - if you have this problem, and have used up other ideas, think about rucking on down to the local Jiffy Lube. Best $150 I ever spent.
 

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Good to hear that the rattle problem was solved. I'm curious about how changing transmission fluid can cure an under-car rattle unless perhaps the fluid level was low, but if it works then one should go for it!
 

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I hope you didn't go to Jiffy Lube. I quit going there back in the early '90's when they put the wrong transmission fluid in my Honda Accord and the transmission was never the same again.
 

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Discussion Starter #5
If I'm not mistaken, the owner's manual calls for no transmission fluid change unless used for severe service such as trailer towing.

Regarding why this solved my problem, I think there may be a clutch or similar mechanism in the torque converter that lock up at around 40 mph. Over the hill fluid may have caused it to chatter or engage intermittently or something.
 

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Hi All,

I have been going crazy, literally for over a year trying to diagnose a rattle from under the car when accelerating lightly through about 40 mph. (4 cyl Limited, 168k miles) I have read countless suggestions about heat shields, etc. One wonderful soul, who i can't identify any more, because I've looked at so many threads, said it might be a torque converter problem and that when he changed the transmission fluid, the rattle disappeared. He was kind of apologetic because the solution was so far-fetched. I have always been skeptical of tranny fluid changes, thinking they were mostly extra profit for the quick-lube places. But I was desperate, and decided to try it. Guess what? It worked. Don't ask me why or how, but it worked, in a matter of a few hours. So - if you have this problem, and have used up other ideas, think about rucking on down to the local Jiffy Lube. Best $150 I ever spent.
Main thing is you got it fixed. Couple of things though.....there is no such thing, IMHO, as lifetime transmission fluid. Also, you're lucky you made it out of Jiffy Lube in one piece. Not the place to go(again)IMHO, for well, anything.
 

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...One wonderful soul, who i can't identify any more, because I've looked at so many threads, said it might be a torque converter problem and that when he changed the transmission fluid, the rattle disappeared. ...
I remember that thread, I'm sure someone will dig it out. He did a full machine flush, not just a drain and refill. Is that what you had done? His thoughts is some friction plates in the torque converter were possibly cleaned by the flushing action.

There's tons of opinion on this topic, but if my tranny was behaving badly like that especially at high miles, I'd give the flush a try. For now, I'm happy with drain and refill type of services (x2 now at 92k miles), fluid looks and smells good and tranny shifts like butter.
 

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there is no such thing, IMHO, as lifetime transmission fluid.
I believe auto industry considers 10 years/100K miles to be "lifetime" nowadays; vehicles are just not built to last, planned obsolescence and all that... IMO transmission fluid should be drained and refilled every 30K miles. While I'm at it, I'd probably change the filter too. When I got my 3rd gen 4Runner (with 230K miles on the odometer!) last February, the 1st thing I did was to change ALL the fluids, trans, engine, diff, power steering, brakes, etc... Everything was black (as expected.)

The 3rd gen 4Runner auto trans takes about 12 QT's of fluid I believe so I've already done 2 drain and refills, 4QT's came out each time. I have another one to go at 240K miles to complete the 3rd and final drain and refill, then I'll probably do one every year. Last summer I also added an inline external trans cooler and since then I've not seen trans temps go above 160F under normal driving conditions. Before the cooler it was regularly around 190F, same as radiator coolant temp since the OEM trans cooler is built into the radiator. It would spike to 220F during summer and stop and go traffic. Not anymore!

When I get a chance I'll add an external trans cooler to the RAV4 too, and get the girlfriend a ScanGauge type of device to monitor all the vehicle vitals.
 

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I believe auto industry considers 10 years/100K miles to be "lifetime" nowadays; vehicles are just not built to last, planned obsolescence and all that... IMO transmission fluid should be drained and refilled every 30K miles. While I'm at it, I'd probably change the filter too. When I got my 3rd gen 4Runner (with 230K miles on the odometer!) last February, the 1st thing I did was to change ALL the fluids, trans, engine, diff, power steering, brakes, etc... Everything was black (as expected.)
............
When I get a chance I'll add an external trans cooler to the RAV4 too, and get the girlfriend a ScanGauge type of device to monitor all the vehicle vitals.
I fully agree with your maintenance schedule but don't understand a 10y/100k lifetime. As far as I'm aware, cars are lasting much longer these days. I remember cars of the 50s & 60s were pretty much used up by 80k or so(yes I'm old!). 150-200k is not uncommon these days. I actually got 300k out of my 1996 Maxima with no major repairs. Regular maintenance is still the key.
 

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Hi All,

I have been going crazy, literally for over a year trying to diagnose a rattle from under the car when accelerating lightly through about 40 mph. (4 cyl Limited, 168k miles) I have read countless suggestions about heat shields, etc. One wonderful soul, who i can't identify any more, because I've looked at so many threads, said it might be a torque converter problem and that when he changed the transmission fluid, the rattle disappeared. He was kind of apologetic because the solution was so far-fetched. I have always been skeptical of tranny fluid changes, thinking they were mostly extra profit for the quick-lube places. But I was desperate, and decided to try it. Guess what? It worked. Don't ask me why or how, but it worked, in a matter of a few hours. So - if you have this problem, and have used up other ideas, think about rucking on down to the local Jiffy Lube. Best $150 I ever spent.

Maybe your talking about my earlier post that went like this
"I have the same issue with my new to us 2010 I-4. This is what I will do in the next month or so. Change out the trans fluid with Amsoil universal 3 times and filter change on the last drain and fill.
About 5 years ago I had the very same issue on my 05 Honda Odyssey. At the time Honda was reflashing the PCM to keep TC lock up from holding low RPM's and they were doing ALOT of TC replacements with little permanent success. One lone poster said the Amsoil trick made it go away. I did his cheaper route and by God it worked like a charm. I like the gas saving low RPM TC lock up on that van and since that time I used that van for a multitude of moving trips of 900 miles one way. To this day the low RPM trany shudder has not shown its self in the least. Right after I did the fix, Honda issues a new all synthetic Trans fluid and alerts dealers to swap out all the old Honda semi synthetic crap. The TC stresses to maintain TC lock up at low rpm because it really doesent have the line pressure to sustain the Lock up as it once did so you get a rapid lock-unlock-lock taking place creating the grumble.
At least in the Honda, this trick worked great and if you think this Toyota grumbleing is bad, the Honda one was so bad you could swear the engine & trany was going to literally rip out of the mounts and bounce out threw the hood and on to the side walk (I replaced both "good" engine mounts). I never used Amsoil before but I have to say, that stuff was like the hand of God healing the Honda permanently! I would never have believed a oil change could make such a fantastic turn around.
Finding an Amsoil dealer around here is a problem... hate to have to pay shipping. "


I have 9 quarts of Amsoil hanging out but have not found the time to change it out yet. I like the idea of letting the engine pump out the old fluid as I add thru the dip stick tube. Not sure which way I'll go yet. To expand on why this works, it has to do with line flow and heat. The shutter is created by the transmissions inability to "hold" torque converter lock up at a low oil pressure due to the low RPM of the engine. Dirty fluid will heat more quickly than clean oil simply due to how an automatic transmission works. Typically heat lowers the viscosity and the viscous valveing in a AT demands consistent viscosity and line pressure to ensure a smooth transition from viscous drive to gear to gear TC "lock up". A good quality synthetic will provide that. The shutter comes from the TC going in and out of lock up in rapid surges. At the moment of Lock Up, line pressure drops drastically enough as to not sustain the lock up of shaft & gears so they release, causing a pressure spike and again a lock up is initiated only to fail again from the drop in pressure.... on and on. This is as simple as I can explained it. A clean filter and oil is imperative to a smooth TC function. I'll try to post how my change out works out.
 

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Well I did the first drain & fill with Max Life synthetic and immediately found the grumble about 60 percent gone. Now I do one more drain & fill w/ Amsoil, then soon there after drop the pan for a clean & new filter and more Amsoil. That should do it for quite some time to come.
 
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