Missed Shift - When do you worry?

[jcsjcs]

I had a blast over the weekend exploring the back roads of Eastern PA. '84 911 Targa - with the top off. The leaves are just changing, the roads were dry and curvy, and this was my first time with the car outside of New York City!

I did have one "Missed Shift" from 5th to 2nd - ugh. Looked like the tach went to about 7000 (that is just an after-image in my head for some reason - not necessarily true.) I reacted very quickly and punched the clutch and found the right gear. No obvious after effects - the car performed fine the rest of the weekend.

Should I worry?

[Oh Haha]

You should be OK. 7000 isn't really that high for these engines. If you don't hear any funny noises don't worry about it. If you spun it up to 8000 I would worry but you should have an RPM limiter so you don't do this.

[Brent Lineker]

The rev limiter will not help you if you blow a shift,it only cuts spark but does not stop your engine from over revs any way mechanically.

[Oh Haha]

Brent,
Yup but I was thinking that he might feel he had free reign to run it up to 8000. Guess I wasn;t looking at what I was typing. duh.

[Jeff]

Does it idle OK?

[jcsjcs]

Idle is the same as always (at least since I have had the car - about 1 month.) Stays stable within about 50 RPM or so.

What's the solution to this problem (other than being more careful)? Shifting from 5th to 4th feels like a bit of a potshot - too far to the right and you get some reverse gear grind, too far left and you blow your engine.

Does a Gate Shifter solve this problem?

[spartan]

get a wevo shifter

[Jeff]

Sounds like you dodged a bullet.
Wevo is a great shifter. You can also look at Rennshift. They both have centering springs (will put the shifter in between 3-4 in the neutral gate) which should alleviate hunting for the correct gear.

[emac]

Got lucky-- I did the same thing and had to replace the clutch. Needed it anyway.

[dad911]

if the shifting is vague, inspect/change the bushings.

$6500 If you bend the valves..... there, bet you shift a little slower now......

[tcar]

Originally Posted by Oh Haha

If you spun it up to 8000 I would worry but you should have an RPM limiter so you don't do this.

RPM limiter won't help a bit with a missed shift.

[Wayne 962]

Run a compression check - it will tell you right away if you have a problem...

-Wayne

[304065]

Run a compression AND leakdown test and report the findings.

It is far better to tear down the engine to replace the rod bolts and any bent valves than to break a rod and blow a window you can put your fist through in the side of the engine case.

[jcsjcs]

How difficult to run compression and leak down at home? What do I need to do it myself?

While I am concerned about the missed shift - I have absolutely no symptoms that anything is wrong or different - no strange noises at idle, normal idle, car is running as always, etc. I expect that the blip in the 7k range did not do any damage but are there any other things I should look out for to see if any damage was done? While I agree I don't want to "blow a window in my engine", I also don't want to overreact with nothing to go on other than the story itself, i.e. no symptoms of a problem.

Thanks for the input!

[304065]

You need a decent air compressor and a leakdown tester. A special adapter for 911 engines that fits into the spark plug hole with a quick-disconnect fitting is nice to have.

Or any local shop can help, it's about a 1 hour task to do it right. Where are you in the City, I can recommend somebody to take it to if you don't want to invest in the equipment.

[jcsjcs]

I live in Brooklyn, but have no problem traveling to Long Island or the other boroughs.

[Eagledriver]

You can tell alot just by turning over the engine by hand. Turn it with a wrench on the fan nut while pushing on the side of the fan belt to keep it from slipping. You should have the same compression feel on all 6 cylinders. If you feel some of them are significantly easier to turn through TDC then you may need to investigate with a leak down test. You can also hear the air hissing out when you do this. It should sound the same on all 6 cylinders and should come from the case of the engine not the intake or exhaust.

-Andy

[Wayne 962]

Just run the compression check - for bent valve damage, it will tell you the same information as a leakdown. Running both is not really necessary...

-Wayne