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So I've had my 2008 Rav4 for a few months now and I love it. It's the V6 AWD 5 speed auto. I did a drain and fill on the trans pan when I bought it with some Valvoline ATF. Works fine but I plan on eventually using this Rav4 to tow my boat. I've been doing a lot of research on these U151 transmissions. People have a lot of different opinions on what fluid to use, I'm wondering if any of the fluids make the shifts stronger/quicker. Mine slides gears like it's trying to keep a full cup of water from spilling over. It doesn't slip like its bad, just very slow gear engagement. I have read about the Sonnax Zip kits, does anyone have that? Does it make the transmission snappier? I've had 2 Mustang's in the past with built autos that shifted so hard the tires would break loose, I don't need it to be THAT aggressive but how it is now I don't know if I wanna tow much with it...My boat may or may not be around 3500+lbs. I had a 98 4Runner that towed it no problem and this has like 100 more HP and an extra gear so as long as the transmission can hold up I wanna take care of it.
 

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You might consider adding a transmission cooler when you start to tow. Your tranny will run hotter with towing, and a cooler made a big difference in my temps (both towing and not towing).
 

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2008 RAV4 Limited V6
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I have always heard that you should only use Toyota WS fluid in these transmissions. Learned my lesson years ago when I owned a Honda Accord. Everybody told me then to only use Honda transmission fluid, and I ignored that advice. It drove fine for a year or 2, but then I had to have the transmission rebuilt.
 

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I have always heard that you should only use Toyota WS fluid in these transmissions. Learned my lesson years ago when I owned a Honda Accord. Everybody told me then to only use Honda transmission fluid, and I ignored that advice. It drove fine for a year or 2, but then I had to have the transmission rebuilt.
You can change fluids as long as the fluid you're putting in does the same thing as the factory fluid. I know for sure you can run "Amsoil fuel efficient OE ATF" but it's $10 a quart. I currently have some Valvoline equivalent ATF mixed in with the old WS but I'm going to be doing a trans filter soon and changing out all the fluid. I guess I'm mostly wondering if anyone has used anything that stiffens up the shifts
 

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2011 v6 Limited, 4WD, Tow Package, Draw-Tite Class 3 Hitch, Black Projector Headlights w/ Xenon
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I don't think the fluid will make much of a difference. For what it's worth, I towed a 3,500lb trailer ~4,000kms and had no issues with the transmission (I have the tow package); but I wouldn't do it again if I had the option!
 

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1. Shift firmness - only a shift kit or valve body modification will firm this up AFAIK. Likely not worth it.
2. This transmission was used in the second generation highlander which was rated to tow 5,000 lb, although likely with a better cooling system and other changes, plus Toyota is overly conservative with tow ratings. You should be fine with 3,500 lb behind, as long as everything else is done correctly (trailer brakes, weight distribution etc).
3. Fluid: the MaxLife is a full synthetic and there are a few threads on BobIsTheOilGuy about it in relation to WS - and many members have been running it for a while with no reported ill effects that I can remember. Be smart and tow correctly and you should be fine. (Says the random guy on the internet!)
 
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