[DreamNforSpeed]

I have a 99 MTX Cougar V6 - and the only mod right now is a Injen intake (cone filter, yadda yadda) - now I had my alternator replaced a few months back and the battery (obviously) - when they hooked everything back up and the computer reset, my RPMs are different than before at the same speeds. I know - no one I've talked to even thinks it's possible, much less can tell me why. Example - in 5th now, the engine runs about 1000 lower than before - I had it to 95 and hadn't broke 4000 rpms. It's more pronounce in 4th and 5th - but I think it's there through the whole gear set. So... what the hell is that? Anyone heard of similar problems? It doesn't degrade the ride or anything else (except I keep having to downshift too freaking often). Help?

 

[exigent]

well.... your gears cannot change ratios magically. Its simply not even open to discussion. If say your at 3000rpm in 5th and going 80mph.... its going to ALWAYS be that way. Nothing can change it short of diffrent gears in the gear box. That and a clutch that slips but youd KNOW somthing was wrong in that case because is would buck and surge. The only two reasonable explainations are as follows. 1. You are mistaken and its done this all along. 2. The tachometer is wrong. If the tach is wrong i dont know what to say about that..... its especially NOT prone to failure. If the tach is off then everything else would be off... the eec MUST know the rpm exactly to be able to keep the engine running. This would be the equivelent to a faulty crankshaft position sensor... the engine would NOT run or perhaps run but VERY poorly. That leaves me to think that the actual needle in the tach may be off... or perhaps there is a short in the wireing between the eec and the dash. A bad ground for example could make the tach read low but it would also make the gauge jumpy and not liniar like it is normally.

I really dont have any advice unfortunatly. Your comment about changing gears too much bothers me though... thats just not posible. Gears cant change ratios in any way.... ever... not without somone opening up the case and installing new gears.

The only other option would be that someone swaped your tranny out and installed a focus gearset....

 

[DreamNforSpeed]

You would be the 5th person to tel me this is impossible (6 if you count myself). This is why I posted it - it is happening, there is no doubt about it. The change in 5th is very noticeable. I had not thought about the RPM gauge - but I doubt that is it, because the engine noise is right (I could feel if the revs were higher than the tach indicates, at least at the differences I am noticing).

I am confounded - the tranny is a mechanical function - gear size versus revolution, but it is. And there is no noticeable problem in tranny performance otherwise. I plan to disconnect my battery again to see if I can recreate the original conditions. It took 3 or 4 days for the rpms to settle at their level - after the computer reset it was just like factory. The guy at the Mercury place told me I was imagining it too.

I will try to get photos of the speedo and tach when I reset the computer - if I never get proof, no one will ever believe me. What the hell is going on?

 

[NorCalCoug]

It's a physical impossibility. There are only a couple of things that can explain it.

1. Malfunctioning tachometer.
-- Whether it's a stuck or miscalibrated needle or a broken tach, that's a possibility.
2. Malfunctioning speedometer.
-- Perhaps the speedo is reading faster than your car is going.
3. Magical Gremlins.
-- There is a slight possibility that magical gremlins have infested your gearbox, replacing gearsets with different ones.
4. Conscienscious thieves with a heart.
-- A conscienscious thief with a heart may have wanted your tranny and could have swapped his Zetec tranny for yours. :shrug:

Is it possible for an automatic transmission to suffer symptoms of engine speed not matching vehicle speed as dictated by gear ratio and final drive? Yes. Why? Because a slipping automatic tranny will cause your motor to spin at higher RPM than normal, producing lower speeds than normal.

Is it possible for a manual transmission to suffer these symptoms?

No, not without auxiliary symptoms that would be a sign of a slipping clutch. Why? Because the link between the transmission and the motor is a physical one, not a viscous liquid one. Gears are solid pieces of machined metal; they have a specific number of teeth on them. Unless some teeth where sheared off of your gears and the gears shrank, it's impossible for the ratio of number of turns from one gear to turn another to change. If there is a 3.4:1 gear ratio, then that is static and won't change. Why? It's a physical piece of metal, not a malleable piece of putty that can change.

That's my reasoning.

 

[gyger]

Have you changed your tires lately.
I know when I put 15's with toyos on
the RPM to speed profile changes pretty noticably
like I'm shifting alot sooner.

But with my 17's on the gearing seems taller/longer

so I guess it is possible.hmmmmm:cover:

 

[DreamNforSpeed]

Originally posted by: NorCalCoug
It's a physical impossibility. There are only a couple of things that can explain it.

1. Malfunctioning tachometer.
-- Whether it's a stuck or miscalibrated needle or a broken tach, that's a possibility.
2. Malfunctioning speedometer.
-- Perhaps the speedo is reading faster than your car is going.
3. Magical Gremlins.
-- There is a slight possibility that magical gremlins have infested your gearbox, replacing gearsets with different ones.
4. Conscienscious thieves with a heart.
-- A conscienscious thief with a heart may have wanted your tranny and could have swapped his Zetec tranny for yours. :shrug:

>edit<

No, not without auxiliary symptoms that would be a sign of a slipping clutch. Why? Because the link between the transmission and the motor is a physical one, not a viscous liquid one. Gears are solid pieces of machined metal; they have a specific number of teeth on them. Unless some teeth where sheared off of your gears and the gears shrank, it's impossible for the ratio of number of turns from one gear to turn another to change. If there is a 3.4:1 gear ratio, then that is static and won't change. Why? It's a physical piece of metal, not a malleable piece of putty that can change.

That's my reasoning.

I know - everything you wrote is true - and there is one more explanation, that I've gone completely insane. Because with all the logic against it, I must insist I have noticed this phenomenon. I did not change tires (although that seemed to be a good guess) - the only non-stock element is the intake, and I cannot believe that has anything to do with it. I will go ahead with my plan to disconnect the battery and document any changes.

I wonder - how do you test your speedo, short of getting a cop to capture you on radar and give you a ticket? Does anyone have a neighborhood with one of those "You are going this fast" radar signs?

 

[NorCalCoug]

Have a friend with a car that's in stock trim (including tires) pace you.