Engine overspeed by downshift
 

Will accidentally shifting to an inappropriately low gear damage something? This can occasionally happen when I'm on the 5th gear, slow down to negotiate a turn, and want to shift to 3rd gear while inattentively shifting to 1st gear.

What part of the engine will be damaged by this move? Rods, main bearing, transmission, or anything else?

How to prevent this kind of overspeed?

Thank you.
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By the way, I'm talking about a stock 4G63T with some insignificant bolt-ons, such as aftermarket intercooler, various gaskets, and head studs.

Rod Bolts will stretch, causing damage to the bearings. The Bolts are the weak link in the stock motor, from over reving.

Valvetrain problems are your biggest issue. Could weaken the springs and cause a valve to fall into the pistons over time...

Try not to shift into 1st, when you mean to go into 3rd... :D

Rod bolts will be damaged but I would be more worried about that if they were under load, in this case they were not.

Mikey

Okay, so it damages the valvetrain and rod bearings. That sounds critical to the engine and it may not last long if this happens often.

I'll try hard to shift to the right gear... hehe

Yeah it's a bad deal to downshift and overspeed the engine.

My GF did a 5-2 downshift at 75mph (meant to go to 4th).

She hit a little over 8k, realized what she did, and pushed the clutch back in.
Real lucky i'd say!

Its not quite as bad as say a 1-2-1 shift persay when racing but you should still avoid it altogether. From my experience the valves will hit the pistons and all hell breaks loose as you can imagine. I had just turbod my honda and installed a b&m short shifter, wasn't use to the new feel of it, and did a pull. Wot in first snatched second bout 6500rpms snatched what I thought was third dumped the clutch and bout went through the front window as my motor went well into the rpm range of a crotch rocket. When I tore it apart it had broken 2 valves bent 3 more and had a nasty hole in a piston and another was beat to crap as well.

Sounds like you're a very good candidate for an automatic transmission. {thumbup}

I spun a rod bearing when I missed my 2-3 shift at the track in my VIII.

That's what mechanics call a money shift. Valves will float and hit the pistons. Worse case the valve head will break off and the cylinder walls will be destroyed. Learn to shift and this wont happen.

Ur engine will go pop along with some of ur drivetrain