lundefinedl

I have had my 3.73 for a few weeks now. I got 25mpg average before and now I get 24mpg. I usually drive about 40 miles a day for work. The only thing that sucks is the engine is insanely loud at 80mph at around 2800 RPM.

frdsinmyblood88

My car runs at 2400 rpm's at 80mph in 5th gear so should I expect it to run 2800 rpm's at 80mph if I use the 3.73 gears at?
Also would it be worth it to get 3.55 gears thats still a upgrade from my 3.31 but I'm not sure if I would be happy with 3.55.

laterider

This thread was exactly what I was looking for as I am seriously considering a change to 3.73 gears. This thread was reading well about the enhanced accel with minimal mpg loss, but then I read the above.

So this goes out to V6 3.73 guys - is everyone having this prob? 80mph is about the max I really ever drive, are you all seeing this problem at 80mph (loud engine, to high rpm???)

jimkaray

Huh? 1 mpg loss at 80 mph is pretty minimal I would say. these changes are the typical results of switching to a numerically higher rear gear. not an actual problem just the normal result of turning the higher rpms. If you are looking to improve gas mileage and quiet the ride at speed switch to a numerically lower gear.

tx_zstang

A loud engine has nothing to do with gears. The engine will rev a little higher at those higher highway speeds, comparing 373s to the stock 331s, but only by a few hundred rpms, similar to the difference perhaps going 70 vs. 75 or so.
With my 373s, the car revs to around 2300 rpms at 70 mph. But even at 3000 rpm, that's not that much louder. Now of course if you have an exhaust that can get loud (and many of us do), then you could have a louder ride that way.

jimkaray

Your exhaust is the primary factor I would agree with and engine RPM would be the second most important factor. Since gearing has a direct bearing on your engine rpm at crusing speed I wouldn't say they have nothing to do with a loud engine (in the example being discussed at least). I would suggest the op run the expected rpm with the gears so he can see how his car will sound with his exhaust system and then he will know if it is acceptable. Of course if he can keep always be going down hill he can pop it in nuetral and it will be very quiet

laterider

I have been playing around in that area - trying to drive 90 or so to get there, probably not the best idea, just to hear the engine. Seems fine.
But I should have been more specific on my question as really the second issue is more important to me. Will I be over stressing the motor running it at 2800RPM when at 80 on long highway drives? This is something I rarely do, but as soon as I change - it will come - road trip!!!
I have found a shop that seems knowlegable on the swap and my next step is to go and see them in person and if all is well, plunk down the cash next month when a bonus arrives (as long as I can keep the $ from the better half). But back to the point, my main concern is the engine. I just want to get all the info before I lay out the dosh...

jimkaray

hmmm, your sig makes me think you tend to throw caution to the wind so why the sudden conservative bent?
You won't be over stressing the motor at all. It will you cause just a little more wear and tear sure but it isn't anything you need to worry about or can realistically measure. If you aren't already doing it I would recommend running synthetic oil in the engine, trans & rear for the best protection against wear and temp extremes. Also, if you have an auto trans a trans cooler will be a help on those hot Florida days.

Joshspony

You guys seem pretty knowledgable about gears. Can I as a question?
I have a V6 auto. In the distant future I want to put a sc on it. Would I be better off going to a bigger rearend or just changing the gears? Either way would that be something that I should wait to do till roughly the same time as the sc?

ABQstang89

run the 3.73's. i would say run 4.10's but if your already set against it...... If you have a future plan for the car it will help you here. If you wanna go tc or sc just save the cash now and get 3.55's.