Gears, Gears, Gears

[woaface]

I haven't quite comprehended the concept of gears...all this "3.55, 4.10" stuff. All I know is what's stock on the Marauder and that most people get a higher gear ratio for off the line quickness, or something. Anyways, could someone please explain all this? That would be great. Thanks a bunch!

[sailsmen]

Go to home, FAQ, Performance Mods.

[woaface]

Thank ya!

[TripleTransAm]

http://auto.howstuffworks.com/differential.htm

In a nutshell, the diff gears transmit the rotational power from the transmission output shaft to the axles. If they were 1:1 ratio, the axles would rotate once for every rotation of the transmission shaft, and the torque on the axle shafts would be equal to the torque on the transmission shaft.

With a gear reduction like 3.55:1 (stock Marauder), the axles rotate once for every 3.55 revolutions of the transmission shaft, the benefit being that the axle shafts also receive 3.55 times the torque on the tranny output shaft.

Going to a 4.10:1 diff ratio, now it takes 4.10 revolutions of the tranny shaft to get one axle revolution, but the torque on those axles is now 4.10 times what is applied to the tranny shaft. More torque on the axles equals more force at the tire contact patch equals better acceleration.

[CRUZTAKER]

I rode in Logan's with 4:30's...dammit I was wrong. I here by no longer preach 4:10's as the best setup N/A.

[gilby04]

Triple,
Very well stated...simple to comprehend.
One comment...I think as the axle ratio is numerically increased, the maximum MPH of the vehicle decreases.
Years ago, I had a '64 Plymouth with a 426 hemi and a 4.89 gear ratio that limited my top end to about 95 MPH.
Just food for thought !

[Hemlock]

IN OVERDRIVE WITH 4.30s , FINAL RATIO IS 3.05 X 5300 RPM = 150 . JUST RIGHT FOR A NICE CRUISE .!! CHEERS.

[Ross]

Also, as the rear gear ratio rises (higher number, fewer rotations, more torque) the engine RPM for any given speed increases, too, right?

[TripleTransAm]

Sounds right. You can calculate the new RPM at any speed with a new gear by simply dividing your speed by the old gear ratio, then multiplying it by the new gear ratio.

Fictitious example:
to find out how much faster your engine will be turning at 60 mph by going from 3.55 gears to 4.10s, take the RPM at 60 mph and divide it by 3.55 . Then take the result and multiply it by 4.10, and there's your new RPM.

[MapleLeafMerc]

And with the higher rpm's many have also added a new drive shaft like the metal matrix one, I think.

[woaface]

TripleTransAm...That was JUST the answer I was looking for.

[bigbaga]

I learn a little more every time I have the time to read the threads on this great site. I spoke to Dennis Rinehart today to inquire about the Stage 1, cost, difficulty of installation etc. What I didn't think to ask was, if I have the 4:10 gears installed will traction control still function?

Hope this isin't too dumb a question.

Big Baga (Greg)

[TripleTransAm]

Originally posted by bigbaga
What I didn't think to ask was, if I have the 4:10 gears installed will traction control still function?

I don't think there is any reason why it should not continue to function.

The traction control compares wheel speeds, not engine RPM. With 4.10s, you're still maintaining the same front/rear ratio of wheel speeds (the front wheels are always turning slightly faster because they're smaller), only your engine is turning faster now because the tranny output shaft has to turn faster for any given road speed as compared to the 3.55s.

I believe the traction control uses the ABS sensors to measure wheel rotational speed. So your tranny shaft could be running at 2x the stock speed for a given RPM because you decided to go with 7.10 : 1 gears instead of the stock 3.55 : 1 ;) but the traction control won't care, he's only paying attention to front and rear wheel speeds.

[Agent M79]

Yes, traction control still works.

TTA's assertion that the TC uses ABS sensors is most likely correct.

Since I've had the 4:10's, I've tripped the TC 3 times. The car would get a wee bit sideways during WOT 1-2 shift and it would snap right back with the TC light flashing at me like an over protective mother.

So, yep. It does.

[gilby04]

AgentM79,

Seems like the 4.10 would reduce the overall life of the engine components due to higher engine RPM.
What effect does your 4.10 have on fuel economy compared to the stock 3.55 ?

[Agent M79]

Gilby,

You can go HERE (http://www.averagegeek.com/Evil_Jim/GearCalc.asp) to see the difference. It works because I cruise at 80mph and with the 3.55's I was at 2400RPM and with the 4.10's I am at 2700RPM.

I suppose the extra 300RPM at 80 will wear faster but I can't imagine a properly maintained engine would have a lifespan significantly shorter because of this minor variation. Perhaps some of the more mechanically learned could chime in on that.

As far as fuel economy goes I have 2 factors obscuring that at this point.

The first is my trip to Atlanta to get the 4.10's (among other things) increased my 'last 3 tank' mpg from 17.8mpg to 19.4mpg because it was 8 hours of Interstate driving where my usuall driving is 50/50 highway/city. So it'll take me a few tanks for this to settle out. Watch my sig, I update it with my last 3 tank average.

Second, as per the experience of other members here, my engine is not "broken in". I am told that when it does, it'll be seat-of-the-pants obvious power-wise and mileage wise.

I am also sending my oil out for analysis at every change to watch for things like premature wear.

[gilby04]

Agent,

WOW...Are you always this quick on the draw ?
Yes, the ratio of 4.10 divided by 3.55 yields the increased RPM.
You're probably right about the ultimate engine life, too.
Since I've never had a vehicle with an all aluminum engine, I'm somewhat cautious at this early stage.
My DTR has just 1700 miles since new on Oct 20th.
Mine screams with the stock gear. Really remarkable.
Acceleration reminds me of my '86 TBird turbocoupe.
Must be (2) hand "white knuckle" time with the 4.10 or 4.30 !!!

[Agent M79]

Heh, Gilby, I just got in when I posted that. Friday is the night out with friends... Funny how getting back used to involve the sun coming up and has been slowly moving closer to the sun going down!

I think for most of the applications you'll see here, the aluminum engine block isn't going to matter much. The only time I see comments made about it are during conversations about putting huge amounts of power through it. Even for the typical supercharger install I don't see it as an issue. For the guy putting massive boost through it tho and looking for totally outrageous power, it may become an issue. Like I said, this is from conversations here, I really have no direct experience.

Mine screamed with the stock gear too. And when I just about learned how to drive it right, I got the 4.10's and the other work done. Gotta say, it is a different car. Well, maybe not different, but 'more' of what it was before.

0-45 (backroads), 0-80 (freeway ramp), and 70-90 (passing) romps are all faster now. Faster speed wise, and faster setup wise because of the programming to the tranny.

Stay here long enough and you're gonna what to do some of these things too!

[TripleTransAm]

Originally posted by gilby04
Since I've never had a vehicle with an all aluminum engine, I'm somewhat cautious at this early stage.


I doubt any of the friction surfaces are aluminum to begin with. My all-aluminum LS1 has cast-iron sleeves (non-boreable, unlike the 99+ LS1s) and I suspect the MM must have the same. Bearing surfaces are not aluminum either. Ditto for valve guides, etc. That pretty much covers all contact points.

[Glenn]

Agent:

I saw your car at Team Ford being worked on by Scott - really nice color. I am very interested in the mpg with the 4:10s. I drive 100 miles a day in my MM and get 20-21 consistent mpg at 70-80 mph with a heavy foot. Keep us posted on your mpg experience. Gears are coming after I install a D.R. X-pipe and then the T/C.

Glenn

[woaface]

Agent! I was showing my mother some of the Marauder's on the site. She liked yours best, and since it's so hard to own a black car here (in the summer...it's HOT, and she's OLDer), she said she'd definitely buy a red one if she had the option. lol...I think it's cool that she was interested.

[Agent M79]

I just used a tank with the 4.10's doing my usual driving routine (50/50 city/hwy) and I got 17.3mpg. This is a pretty typical for me at this point.

I have a higher last-3-tank average because the Atlanta trip is still in there where I got a 20.1 going (with 3.55's) and a 20.3 coming back (with 4.10's).

Early indicators are that there won't be an impact but I am keeping an eye on it.

[Bigdogjim]

Originally posted by Agent M79
I just used a tank with the 4.10's doing my usual driving routine (50/50 city/hwy) and I got 17.3mpg. This is a pretty typical for me at this point.

I have a higher last-3-tank average because the Atlanta trip is still in there where I got a 20.1 going (with 3.55's) and a 20.3 coming back (with 4.10's).

Early indicators are that there won't be an impact but I am keeping an eye on it.

M79-When I drove to Marauderville (Ennis,Tx.) in September I had 3 MM with 4.10's follow me(along with at leat 20 others:)) anyway we checked fuel at each time we refuled and found I used about 1-2 gallons less per 300 avg. miles. Not a huge differance. We checked for 3 days about 1200 miles give or take:)

[gilby04]

Agent,

I'm here (on this website) to stay. Everyone's input, large or small, is invaluable. I've learned HUGE in just (1) month! The more I read what you guys have done with gearing, chips, etc, the higher the anticipation.

Bigdog,

I assume you have the stock 3.55 gear, like me.
Even though 1-2 gallons is a not huge (absolute) difference, 1-2 gallons represents a 5%-10% variance in a 19 gallon fuel tank.

[bigbaga]

Don't you just love this site? I spend so much time reading the threads my wife is starting to think I have a girlfriend! Well, That's probably why we have a member that calls his car "The Other Woman".

Thanks to all for the answers regarding the traction control issue. Now that I'm getting so "geeked" about the Stage 1, I cant wait until I have the extra $ to get this Rinehart kit ordered. Having the holidays sneaking up on us, the extra $$ most likely just wont happen. Now, to find someone I trust to install the gears.

I just ordered the kit from Eastwood to paint my calipers gloss black. (on sale now) I just hate how they look now, but I will wait until spring when the winter tires and wheels (going on next week) come off to paint them.

[CRUZTAKER]

Originally posted by Bigdogjim
[B]M79-When I drove to Marauderville (Ennis,Tx.) in September I had 3 MM with 4.10's follow me(along with at leat 20 others:)) anyway we checked fuel at each time we refuled and found I used about 1-2 gallons less per 300 avg. miles. B]

I was one of the 4:10 drivers, and true, we all checked every fill up, and every time it was the same. I averaged 22 and the stockers averaged 24. At this point I wonder if 4:30's would have been .....funner....

Barry

[Glenn]

Agent:

Thanks for the update on the 4:10 mpg. I would still like to keep this thread going for awhile. If anyone else has mpg readings between the stock 3:55's and the 4:10's please posted it here. It looks like we may have somewhere around a 10% gas mileage difference for most MM???

Thanks,

Glenn

[SergntMac]

How do you get more push from less gas? Here's a quick history lesson from an old guy who's a 2x MM owner.

I think it's reasonable to expect a reduction in MPG once 4:10s are added to a bone stock MM. Fondness for getting into the throttle is my customary expectation once a Stage I kit and a dyno tune have been added. Of course, this will skew MPG figures for the short term, but we all eventually settle down for a serious MPG study. That's when you see that despite your new and more efficient gear ratio, you still stab the throttle to get moving. You move sooner and quicker, yes. But, you seem to be burning more fuel to do that. Why? Well, guess what, you have a new "performance leak" and it's called torque converter.

The OEM converter for the '03 MM is an 11" unit that suffers from "balooning" over 6000RPM. It gets all out of shape and starts to act like a football at high RPM. Since the '03 was delivered with RPM and speed limiters in place, this side effect was not a concern for the designers. However, once we got our fingers into the PCM, we side steped those limiters, and issues with drive line stability came to the surface.

Our "drive shaft vibration" became the chief issue, we all got a taste of that high speed buzzing, and we all wanted it fixed. I think Zack was the first to blow a tailshaft because of it, but we all paid attention and did our homework. The drive shaft issue overshadowed the torque converter shortcomings, and we rarely mentioned it specifically at all.

I don't have any 411 on the '04 torque converter, except that it's now an 11.25" unit, and supposedly "smoother." FMC may have fixed the "ballooning" issue, but they haven't increased the converter performance. The OEM torque converter converts engine torque at a 1:90 to 1 ratio (or something very close to this).

That's better than the General's average of 1:53 to 1, but it's still not satisfactory when moving a "heavy car. It takes a lot of torque to move 4200 pounds from a dead stop, and it takes a lot a lot to keep it moving on the highway. We lose a lot of that torque, maybe as much as 25%, in the power train of a bone stock MM.

I love the "Stallion" torque converter from Precision Industries. I may be biased here because I've owned and driven two MMs, both with Stallions, but both performed like you wouldn't believe. The Stallion converts torque at a whopping 2:50 to 1 ratio (or something very close in that area) and that reduces your driveline power loss to something closer to 15%.

This is not a cheap mod y'all, maybe 750 bucks not including install labor. However, Precision Industries offers a two year warranty that allows you to return your Stallion to them for testing and updating for free. You pay shipping. Check it out here... http://www.converter.com/stallion.htm

Once you upgrade your torque converter to something like the Stallion, your "above 20" MPG should be restored, I'm sure of this. With all the junk I have installed on my MM now, my recent OTR trip to meet y'all in ATL netted me an average of 22 MPG getting down there, and 21 MPG getting home, cruising an average of 80 MPH. I think this is possible only because the torque converter delivers more power to the rear end, and I use less throttle to get up to speed.

"Short answer? You get more push from less gas"...IMHO.