WTH is a "5TH Gear Switch"?

Why is this in a toyota newsgroup?

Probably lets the instrument panel know when the car is in the highest gear so that that infernal upshift light isn't always blinking at you. At least that's what it was for on VWs.

nate

I forgot. You don't know anything about cars.

At all.

If it is near the shifter opposite the reverse switch, I'd guess neutral safety switch.

Oh, no. In the manual it does say 5th gear switch, but doesn't say anything about what it does.

I did find a couple web sites; two said it bypasses the EGR valve, and a Nissan site said it cuts in a rev limiter (the guy was going to wire a momentary switch on the clutch pedal to have the rev limiter on all the time when he presses the clutch...I thought I was a geek...)

Hmmm, are there 3 switches on the tranny - reverse lights, neutral safety switch, and 5th gear switch?

I can't think of why they would want to bypass the EGR valve only in 5th gear, unless they were getting EGR surge during a steady cruise and the EGR is electronically modulated instead of vacuum modulated. The rev limiter theory makes a little more sense, but again, limiting revs is usually more important in lower gears where someone is more likely to miss a gear, and rev limiters are usually more dependent on throttle position than selected gear.

Only two, afaik. 5-speed manual, safety switch at the clutch pedal...

From what I have seen, it seems they shut the EGR down. Probably for two reasons; first, if you're in 5th your probably running in the engine's most efficient range and emissions are nil, and/or shutting it off gets better fuel economy and a bit more response. I know the last part because...

er, let's see...1987-2008=21 years. Past Statute of Limitations? ...

I bypassed the EGR on a new '87 Corolla. Thing had a miss right around 45 MPH and that cured it!!! It was a carb'd model and just didn't have the response of the Hachiroku!!!

In that case, I'd vote for the EGR theory.

"OD" Overdrive light maybe ?

Perhaps on an AT, but these were on Manual transmissions.

I still haven't really found anything definitive on this!

Why not disconnect the switch and see what happens (or doesn't happen) when you shift to 5th gear? Odds are that you won't blow the engine or transmission.

Several of my manual trannies have had an OD light when so equipped. Volvo for sure and I don't remember on my Mazda.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

Does it have an 'upshift' light? If so it might be there to say 'in 5th gear, can't upshift any more'. I check OEM mazda service manuals and wiring diagrams to get a better clue later.

I think I'll have to check the dealer. Nope, no Upshift light (THANK GOD!!! I dismantled the dah on a bran new Jetta in 1985 because of those stupid things!)

It was disconnected! I reconnected it.

I did notice improved throttle response in 5th gear on the highway. I'll keep an eye on the fuel economy...

I am going through the 1989 mazda MX6/626 OEM shop manual. I cannot find anything called a '5th gear switch'. There is however an entry for a 'speed switch 113mph (180kph)'. not much other info on it than showing it as a switch on wiring diagrams.

LOL! I DON'T WANT ONE OF THOSE!!!!!

Japanese cars are made to cut out at 180kPh by Japanese law. That's the switch that, I believe, kills the fuel pump once that speed is reached.

Don't have one on my '85 Corolla GTS. Hit 130 MPH with that car once...

Oh, don't forget the legally required in Saudi Arabia speed switch that turns on a very loud and annoying buzzer at IIRC 62 MPH...

They do put "soft" speed limiters (that do progressive fuel cut in the EFI) in some 'economy' cars that come equipped with regular tires good for only 110 MPH or so, so you don't get out on the Autobahn or a straight arrow West Texas Highway running flat out and overheat & blow a tire or two. The fifth-gear switch moves the rev-limiter redline in

5th down to the max tire safe speed.

This is why they put the Z-rated high-performance tires on the hot cars - no speed limiters - and the tire shops refuse to put any lesser rated replacement tires on them, because the tort lawyers make the shop owners unwilling to take the risk.

If the car calls for Z tires and the tire shop only puts on S-rated tires (still good for any road-sane speeds in the US) or unrated tires (still good for 80-plus MPH) and the tire blows at speed and causes an accident, the tire shop can be sued.

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I remember, about 15-20 years ago, the race they have outin the desert in Nevada. Some Dr. shows up with a brand-new Ferrari, and the inspector says, no, you have the wrong tires and no fuel cell. The Dr gets into an arguement with him, they call a stweward over, and then a race official. The Dr had run the race before, so the official waives the rules.

Guy blows a tire, goes off the road, he gets out, the tank catches fire and the wife dies.

Dr sues the race officials.

How stoopid can you be?