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Discussion Starter · #1 · (Edited)
I've been stuck with 3.55's for almost 2 years now in my 10' RCSB 4x4
and the time has finally come to upgrade!

I've been running 28" M/T DR's on 17" wheels at the track to drop my effective gear ratio to around 4.30:1
The 295/45R17 Mickey Thompson ET's (x4 for my 4x4) shaved 5 tenths off my quarter, and got me into the 13's (13.8/98.5)
...along with the basic intake/exhaust/tune mod's everybody runs.

Most recently I stepped up to an Edge Torque Converter that stalls at about 3000 rpm,
and dropped another 3 tenths off my 60' down from 2.1's to 1.8's but traction is dependant on perfect conditions/prep now.
My new headers just arrived this week (JBA coated shorties)
and before I go much further adding power it's time to address my traction issues due to my open rear diff and 3.55's
I'm getting to the point that I often need to use an AWD (4WD Auto mode) and 4 drag radials for traction.

Since a Locker will keep me from doing a 1 wheel peel,
I may as well upgrade my gears when the rear carrier comes out in favour of a Detroit Tru-Trac limited slip.
I've been doing some calculation,
and I "think" ideally I should be aiming for about 5800 RPM at the finish line in a 1:1 3rd gear. Right?
I'm currently running a Diablo 93 tune, shift points are maxed out 6200-6400.

So what do you think? 4.56's too low? are 4.10's a better choice?
For daily driving I roll heavy 305/50R20 Terra Grappler's on stock 20's
90% city commuting and very rarely see any highway time.
I've recently found some good on-line calculators here...
http://www.hotrodpitstop.com/tool.php#6
Not sure what number to use for torque converter slip so I just used 10%



Here's where I'm at currently with 3.55's on my 28" tires:
3rd gear is falling on its face at 4600 rpm at the traps

with 4.10's put me at 5300, much closer to being in the powerband at the traps

and 4.56's put me right on the edge before 4th gear kicks in after crossing the 1320' mark

Anybody here running lower gears for racing confirm those numbers?
That last thing I want to do is end up shifting into 4th (overdrive)because I've gone too low with 4.56's.
I have to regear both front and rear diffs,so I need to get it right the first time.
I suppose if I end up with too short a gear,
to correct it I could just get new taller tire 30"-31" tires and sell the 28's.

FWIW, my best times at the track on my heavy Grapplers/20's are 14.4's with 3.55's
I bet I could get high 13's on them on 4.56's and my new headers :D
 

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By the calculations above it seems the 4.10's would be the best way to go but I'm new to all of this as well and have been trying to learn on the fly. I have the 3.92 and am at the top of 3 right before the 1/4 line but I have not adjusted the shift point yet. My best time is on the stock 20's and goodyears was 14.465 at 97 mph uncorrected. I have also been thinking of finding a set of m/t's. Hope you get it right!
 

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90% city = 4.56's! How tall are your street tires?
 

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Discussion Starter · #5 · (Edited)
My street tires are 305/50R20 Terra Grapplers
they are 12.2" wide by 32.2" high and on mystock 20's weigh in at over 90lbs ea.

I currently run 14.4's on them at the track
..and thats at 2500'+ DA, would be high 13's at sea level.

I'll probably turn them at 2300+ rpm on the highway with 4.56's, but that wouldn't be very often.
My truck is primarily my city commuter/weekend warrior and wont see 5th gear very often.

I run a 93 octane tune all year round, never less than 94 octane fuel,
my throttle boost and shift points on my Diablo Trinity are maxed out.

Fuel economy has never been a concern, go fast or go home.

Although I've never re-geared a truck for the track,
I have done many Jeeps with 4.56's and ARB air lockers front and rear,
so I do know and appreciate the performance benefits of a gear swap.

I was a Jeep Jamboree Trailguide for almost 10 years
my last ride....built by myslef from the ground up except for the axles, I leave that to the pro's

 

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I think you should think about where you want to go next with your mods. You need to base your gears on your final goal. If you add a cam-n-heads and/or power adder into your equation, you'll likely run out of gear at the big end or cross the line at an RPM that is not optimal.
 

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I would go with the 4.10s. do your M/Ts actually measure out at 28" or closer to 27" when aired down? Also, wouldn't your trap mph increase with a quicker E/T? If your E/Ts dropped to 13.4 you'd be crossing the traps around 101 and that puts your rpms up in the 5600-5700 area. Am I way off in my thinking?
 

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Discussion Starter · #8 · (Edited)
This is why I'm asking for "Real" results from someone that's done it rather than guessing or relying on calculators.

I've read that a gear reduction only effects your ET,
and traps speeds remain aproximately the same if all other parameters remain equal.

With the limited experience I have, I believe that to be true.

I also believe that regardless of power adders or internal upgrades, like cam/heads,
RPM at the finish line will remain constant with tire size x gear ratio x trans gear ratio.

I have a bud with an SRT10 Ram who runs 4.56's and M&H 390/40R17 DR's (29" Tall) and a 100 shot
so there's no way I'm going to run more power than him, so I cant understand how 4.56's could be "too much" gear for my Ram with substantially less power.



As I said before, should it be too low, although I cant imagine it
an easy fix is to just go to a taller drag radial, right?
 

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Discussion Starter · #10 · (Edited)
Tires are WAY cheaper to swap out than Gears if you dont get it right the first time.
we're talkin a couple hundred$ vs a couple thousand $$$ in labour charges alone.

Having a 4x4 makes it twice as expensive if you're not careful ;)
 

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I'd personally go with the 4.10's. Even with the 4.7L I will most likely go to 4.10, if I had the hemi with the extra numbers I'd definitely choose 4.10.

I'd choose the gear that will get you what you want on the street, then adjust your slicks to meet the final ratio you want. You don't want to set it up for the track then have it not as driveable on the street as you'd like. Like you said, you can adjust tire size easily, but I'd adjust it on the track.

Realistically, even with 4.56 it wouldn't be that bad on the street though.
 

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Discussion Starter · #12 · (Edited)
That's exactly why I made a point of saying this is not a highway truck that will be spinning 2300 RPM in 5th gear at 70 mph for hours on end..

I only use the truck occasionally to-from work and it wont likely ever even get to 5th gear.
Getting from intersection to intersection in the city is a lot shorter than a quarter mile.
Performance>Economy are my priorities and I cant imagine why 4.10's that are barely better than 3.92's would be the best choice.

Gas milage would be the only down fall if I was spending the majority of my time at highway speeds.

My Ram is two years old and has about 12k miles on it, it is not my only vehicle.
 

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^I understand, but you will end up with the same final ratio either way by adjusting tire size, so it really doesn't matter which you choose. Just that with 4.56 it'll be slightly worse on the highway. I understand you don't care about that, but there's no downside to the 4.10's, so I don't know why you'd not go with them.
 

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You could even run like a 26" diameter slick and end up with the same final ratio as running 4.56's with your street tires. My point is it really doesn't matter for the track, you can adjust your slicks to meet the final ratio that you want, it's on the street where you don't want to run tiny or huge tires that you should gear it to what you want. That's my opinion anyway. Final ratio is what really matters. If you run 26" slicks with 3.55's vs. 32" tires with 4.10's, the 3.55 setup is "better" for the track probably, so it just sort of depends on the entire setup

Either are fine for the track, even 3.92 or 3.55 are fine for the track, you can achieve the same final ratio with tire size.

It sounds like you have talked yourself into 4.56 though.
 

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I'd go for more rpm than 5800 thru the traps. 6300 with you're tire dia and 100 mph would work out to 4.77's. I think 4.56's would be perfect and even if a little short you'd just have to put a taller tire which would look better anyway.
 

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Discussion Starter · #16 · (Edited)
It sounds like you have talked yourself into 4.56 though.
What I'm asking for, in the "Drag Racing" section,
is performance experience/opinions from those who HAVE raced with 4.56's.
...not what gear would be more streetable. :doh:

chefred, kay-9, Randtx ? are you guys around still?
or is my question is better suited to hardcore racers at NADodge.

Yes I want to run 4.56's, why? I've done it before on other vehicles I've owned,
and because there are already many Ram's running 3.92's,
So are 4.10's going to be a significant advantage over them?, for $3000+? Hell no!

If I'm going to "upgrade", I want to pick up as much RPM as possible for the $ without going over right?, if 5900 rpm costs the same as 5300rpm, why would I waste my time and money by settling for less?

I could have upgraded my torque converter from 2300 to a stock R/T 2600
but chose to go one step further for a reason, and now I can bury them off the line with a 2800-3000 stall.

Why not do the same when it comes to re-gearing???

[edit note]...just for the record, I have only 12k miles on my 2 y/o Ram
and have 3 other vehicles to drive, all for different needs/requirements.

only requirement for this truck is to be FAST, all the time!
I run a performance tune and 94 octane all year round, 4WD in the Winter
and drive the hell out of it always...lucky to see 10MPG and I dont care :p
 

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Final ratio will be the same either way, but choose whatever you want, you asked so I'm just giving advice. If there's no difference on the track, then why would you purposely choose the option that is less streetable?

That's what's :doh:

Actually, the setup with smaller tires will be faster because the tires will be smaller which means they are lighter.

The 4.10's with the smaller tires to give the same final ratio that you would go with by having 4.56's will be better performing when run side by side. Also, 3.55's with tiny tires to give the same ratio as those above would be better performing again(as long as you can keep traction, but most likely it wouldn't be an issue with slicks, especially if you use 4wd).

I agree to go with the best option.

If you want to "upgrade" to hit a certain rpm at the gates without spending a lot of money then just change the tire size. You'd run faster with 3.55's and small tires.
 

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Discussion Starter · #18 · (Edited)
WTF?

final drive ratio is the same ? no difference on the track?

I already have the 28" tires, def not going smaller
so the only factor is the gearing, and I NEED a locker

4.10's = 5300 rpm at the traps
4.56' = 5900 rpm at the traps

do you not comprehend that?

my city commute is from stop light to stop light
that's actually LESS than a quarter mile.

so how is a lower gear that's better for the track, less streetable?
 

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Discussion Starter · #20 · (Edited)
:doh:

I didnt start this thread asking what tire size I should run, I'm under-geared with open diffs.
I need a rear locker to help avoid a one-tire-fire, and want to take the carrier swap opertunity to change gears at the same time.

I purposely bought a set of (4) light weight 295/45R17 DR's to drop my effective gear ratio from 3.55:1 to ~4.30:1 two years ago.

With my Drop, if I go any lower on my tire height I'm going to bottom out :D



I want to drop my 13.8 to mid 13's, on my DR's
and I want to be able to run my 20's occasionally and go from 14.4's to high 13's
I would like to be able to do it in 2WD whenever possible, which inst likely with an open diff now that I have a higher stall TC.

My heavy 305/50R20 Grapplers best time on 3.55's is 14.4 but traction with open rear diff is hit and miss... all terrain tires suck for traction in 1 wheel drive
 
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