I haven't paid much attention to trucks since I bought mine. I couldn't imagine pulling a trailer with 159 hp - That explains a lot. The V6 has about the same HP as my 4.7 V8 - I have had a lot of issues with my Dakota.

The TSB was originally for certain Tacomas prior to 2010, and then extended to 2010 models. It was for those Tacomas with a three-leaf rear spring set with a particular part number. If customers complained of problems like you mentioned, dealers were to contact Toyota and replace them with a four-leaf set. Unfortunately I'm not at home right now and don't have all the particulars, but, if you go to the Tacoma forum (tacomaworld.com), you can find the info you need. That's where I got it from.

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2007 22TB HiLo
2010 Toyota Tacoma