Quick ATF drain bolt question
 

Yesterday I did an automatic transmission fluid drain and fill on the family 2009 Honda Fit, which was bought with 2,000 miles on it (sold as new, but with a heavy discount since the dealership had used it as its body shop loaner). We had not replaced the ATF on it before, and it now has just over 58,000 miles.

I had great difficulty breaking the drain bolt loose and had to brace myself against the front bumper to do it. I cannot believe it was torqued in place at just 36 ft-lb. That torque value is given in the ATF replacement DIY on this forum, and also in the bootleg electronic FSM that is mentioned here from time to time and covers the Jazz/Fit for all regions other than North America. However, the bootleg FSM shows a completely different drain bolt with 18 mm hex head, instead of a round head with recessed square for a 3/8" drive ratchet.

Can anyone confirm that 36 ft-lb is the specified torque value for US/Canadian Fits? Is it normal to have this much trouble breaking the bolt loose? I torqued it back in place to 36 ft-lb and it still felt kind of loose; then, just for kicks, I set the click-type wrench to 45 ft-lb and that still felt significantly less than the break-loose torque.

First off, I don't own a CVT Fit so I don't really know if the drain plug is a pipe plug or a plug with a crush washer?



Was there sealant on the treads that may have "glued" the plug to the case? Assuming the case is aluminum and the plug is metal? Two dissimilar metals can "weld" themselves together. Based on being an 8 year old car, and if the plug was installed dry it's a possibility?

This is a Fit Sport with the five-speed automatic, so the drain bolt has a crush washer. I don't know if antiseize or threadlocker was applied; there were a couple of small gray spots in the threads on the bolt when I took it out, but the magnet was also very dirty. I'm pretty sure the case is aluminum, but the bolt threads were very bright, so I suspect a nickel alloy. Welding together through electrolysis sounds like a plausible theory.

Absolutely normal. I've even ruined a Snap-On ratchet on a Honda transmission drain bolt. Now I use a long breaker bar and use a quick jerk motion with follow through to break them loose.

Wipe the fuzz off the magnet, that's normal.

36 ft lb is correct.

Threads CLEAN. No sealant of any kind, no anti seize of any kind.

The crush washer does the job of sealing.

Don't go tighter than spec, you could cause serious damage. I've actually seen a trans case cracked at the drain bolt area.

The reason it feels unusual during tightening is because the soft aluminum crush washer is becoming squashed (crushing to form a seal) as you tighten the bolt.

Look up 'breakaway torque' for an explanation of why it almost always requires much more effort to break a bolt loose than it did to torque it.

Perfect response ezone.

Ezone--many thanks for this. I'll invest in a breaker bar.

I'll also try the crush washer at 36 ft-lb at the next drain and fill, which should be fairly soon (within the same oil change interval) since I am trying to get the old brown ATF-Z1 out through multiple drains and fills instead of bleeding and filling through the oil cooler loop.