Another gear post, but with a slight twist

[lnferno]

So everyone knows the 3.92 gears are quicker off the line than the 3.21s, but if both trucks are going between 40-60 MPH and then go WOT, which one would be quicker to 120MPH?

 

[69GWC]

Good question, I would guess the 3:92 truck still.
Now if the 321 truck was in a lower gear in the transmission and that same gear ratio was to low for the 392 truck the 321 truck would get the jump on it. at the giving speed.

You know how if you are just at the wrong speed and it only drops to 4th instead of 3rd gear.

Would like to see to stock trucks race a few different times from a stop and then at like you said 40ish mph .


my 2 cents.

 

[RLJ10X]

Since the 3.92 has the mechical advantage, theoretically, the 3.92 should be faster.

 

[yortnodnarb]

But would the 3.92's be revving too high and not be in the optimal power range?? Would it have enough legs to effectively get to 120?? The 3.21's would lose the 0-60, but might be in a better rpm range to outrun the 3.92's 60-120.

 

[69GWC]

Ha no they both stop at 105mph because if the factory govner..lol


Someone posted before that once the trucks go into 3rd gear that the transmission gearing pretty much equals out the difference in the rear end gearing between 8sp trucks.
have no idea if this is fact or was just a thought.

 

[crackerjack1957]

The ratios are (this is for all 1st gen 8HP transmissions to include the 8HP45, 845RFE, and 8HP70-and the 8HP90 in the Hellcats):

1st-4.714:1
2nd-3.143:1
3rd-2.106:1
4th-1.667:1
5th-1.285:1
6th-1.000:1
7th-0.839:1
8th-0.667:1
R-3.300:1

The 2nd gen 8HPs such as the 8HP75, which I strongly suspect will appear in the 5th gen Rams, have a wider range:

1st-5.000:1
2nd-3.200:1
3rd-2.143:1
4th-1.720:1
5th-1.314:1
6th-1.000:1
7th-0.822:1
8th-0.640:1
R-3.456:1




Gear ratios 1 2 3* 4 5 6 R
545RFE / 65RFE 3.00 1.67 1.50 1.00 0.75 0.67 3.00 or 2.21
Aisin AS68RC 3.74 1.96 1.34 1.00 0.77 0.63 3.54
66RFE / 68RFE 3.23 1.84 1.41 1.00 0.816 0.625 4.445
* “Prime” gear used for kickdown only

 

[Wild one]

There's a couple nitrous trucks that went from 3.21's to 3.92's and are actually slower at the track.My truck didn't gain squat when I went from 3.21's to 3.55's,and i'm still kicking my ass for going to the 3.55's

 

[69GWC]

There's a couple nitrous trucks that went from 3.21's to 3.92's and are actually slower at the track.My truck didn't gain squat when I went from 3.21's to 3.55's,and i'm still kicking my ass for going to the 3.55's

Do you think it gained anything off the line ?

Just wondering about regearing after going to a larger tire.

 

[Wild one]

Do you think it gained anything off the line ?

Just wondering about regearing after going to a larger tire.

My best 60ft with 3.55's is 1.68,my best 60 ft with 3.21's was 1.69,so nope,but I also spray my 75 shot right outta the hole.Nitrous generates torque almost instantly.In your case if you're going to a bigger tire,re-gearing is probably wise. I run a short 28" drag radial at the track and 30" tall street tires,so on paper my effective ratio is almost the same as 3.92's with stock 33" tires

 

[gofishn]

3:21 would be better.
Reason everything below 3:55 are called Highway Gears.

Engine works less, at same highway speed, leaving more rpm's availabe, until redlined, to increase speed.

 

[yortnodnarb]

Do you think it gained anything off the line ?

Just wondering about regearing after going to a larger tire.

I've never had a truck with 3.21's but my last 2 had the 3.55. My current truck has the 3.92's and yes you'll benefit greatly re-gearing to 3.92's. This thing pulls like a mack truck compared to the 3.55's and my dad's longhorn with 3.21's.

Downfall is the mpg drops off fairly significant though once above 65mph, but I'm rarely in that mph zone so it doesn't really affect me.

 

[lnferno]

So a tuned truck with 3.21s vs a stock truck with 3.92s would be pretty even until 60 mph? Then the 3.21 truck would pull away?

 

[69GWC]

I've never had a truck with 3.21's but my last 2 had the 3.55. My current truck has the 3.92's and yes you'll benefit greatly re-gearing to 3.92's. This thing pulls like a mack truck compared to the 3.55's and my dad's longhorn with 3.21's.

Downfall is the mpg drops off fairly significant though once above 65mph, but I'm rarely in that mph zone so it doesn't really affect me.

Were those trucks both 6sp or both 8sp trucks. ?

 

[lnferno]

Were those trucks both 6sp or both 8sp trucks. ?

Edit

 

[gofishn]

So a tuned truck with 3.21s vs a stock truck with 3.92s would be pretty even until 60 mph? Then the 3.21 truck would pull away?

Moot. No one races to top speed over 10 miles. Races tend to be 1/8, 1/4, 1/2 mile distances.
3:92 is more fun, form dead stop. 3:92 will pull more weight, easier.
3:21 will also pull the weight with 8speed, due to gearing of drivetrain. but. super heavy weights, on an inclined, the 3:21 may fall down.

EMpty cruising, highway speeds 3:21 is the way to go.

what do you want/need your truck to do? Highway Cruiser, fuel economy queen, drag strip terror, stop light 2 stop light bandit, Pulling Behemoth regardless of load or incline?
There is no one fits all when it comes to truck gearing.

Even if I were not a Dodge guy my entire life< I would still have bought this truck.
I looked at fords, even chevy, but too wimpy power plants, for me. V-8Hemi with 395HP and 3:92?
Now I will trade in my 99 V--10 2500 and get something little easier on gas, that will still pull whatever I need.

 

[yortnodnarb]

Were those trucks both 6sp or both 8sp trucks. ?

I thought of that after posting, 1 was a 6sp so that doesn't really count. But the other was an 8sp and my dad has had a few 8sp trucks and none with the 3.92. My current truck is noticeably different than any of them.

I'm not sure if I would buy a truck without 3.92's now that I've had 1. I was leery before I bought it because I was afraid of a big mpg hit compared to the others. But comparing mine in stock for to my dads in stock form, there wasn't a significant difference. Not enough to beat that off the line tug that's for sure.

 

[69GWC]

And this is where is gets confusing, we have one guy how has been to the track posting in the 1/4 mile the gear choice did not make a difference at all so I dont see how a DD you could tell much or any difference if you cant see any in a timed 1/4 mile. ?

Now I can see once bigger tires are installed or if you are pulling heavy having more grut off the line but if these 1/4 mile times hold true just empty apple to apples the 8sp takes away the advantage in the rear end gearing.


again just talking out loud here.

 

[lnferno]

This is where I'm coming from. My truck currently has 3.21s. I'm going to get a custom Jay Greene tune. I'm contemplating getting 3.92s as well, but I'm wondering how a custom tuned truck with 3.21s would fare against a stock truck with 3.92s both 0-60 mph and in the 1/4 mile.

I know I can't eat my cake and have it, too. I'm not going to lie - the MPG is pretty nice with the 3.21s, but at the end of the day, a quicker truck is the higher priority over a MPG princess. I know some may say get the 3.55s. That's not under consideration. I'm probably going to go with 3.92 gears, unless anyone has a compelling reason why a custom tuned 3.21 geared truck would be sufficient over a custom tuned 3.92 geared truck.

 

[Wild one]

And this is where is gets confusing, we have one guy how has been to the track posting in the 1/4 mile the gear choice did not make a difference at all so I dont see how a DD you could tell much or any difference if you cant see any in a timed 1/4 mile. ?

Now I can see once bigger tires are installed or if you are pulling heavy having more grut off the line but if these 1/4 mile times hold true just empty apple to apples the 8sp takes away the advantage in the rear end gearing.


again just talking out loud here.

The fastest bolt-on NA dodge around is Kyle Tingles truck and he went from 3.92's to 3.55's to get his truck to an 11.98 in the 1/4.He might even gain a little more if he goes to 3.21's .First gear becomes virtually useless with 3.92's once you start bolting on a bit of power.With bigger tires it's another story though,there the 3.92's shine.

 

[69GWC]

Thanks for that info Wild one its great info.
The 8sp is just a kickass transmission..lol