3rd Gen Engine and Drivetrain -> 2003-2007 5.9 liter Engine and drivetrain discussion only. PLEASE, NO HIGH PERFORMANCE DISCUSSION!

3.42 Gears

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Old 07-17-2008 | 04:35 PM
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3.42 Gears

has anyone else made this swap?????

There has been very little talk about these in the last year...i know of like two people on here who have done it and they seem to love it..

Taller tires arent an option for me unless a tire company would step up.

I can do the gear setup myself so for around 1100 bucks i think i can have these things in and be able to cruise unloaded at a decent RPM.
Old 07-18-2008 | 06:44 AM
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still no one i assume
Old 07-18-2008 | 08:08 AM
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I did the swap and love it, wish it had of dropped the RPM even lower.
Old 07-18-2008 | 09:44 AM
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how many rpm do you turn at 65,70,75, and 80 approximatley?
Old 07-18-2008 | 10:43 AM
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1900 @ 65 mph, 2000 @ 70, 2150 @ 75, 2300 @ 80.
Old 07-18-2008 | 12:03 PM
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awesome, thanks


How is acceleration at 45 mph in 6th gear? will the turbo spool? I find mine starts around 1300
Old 07-18-2008 | 01:49 PM
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Levi...
If I may make a suggestion... The 3:42 gears are not for towing and I see you have a DWR so I will make the assumption you tow. From that look into a Gear vendor over drive unit. It is a full 15% reduction, can use to pull, and you still have the stock ratio to pull any load you need. They are certainly more money, but there is no comparison in what it will deliver. Had one and loved it to the max!
Old 07-18-2008 | 04:10 PM
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Originally Posted by Mr Bee
Levi...
If I may make a suggestion... The 3:42 gears are not for towing and I see you have a DWR so I will make the assumption you tow. From that look into a Gear vendor over drive unit. It is a full 15% reduction, can use to pull, and you still have the stock ratio to pull any load you need. They are certainly more money, but there is no comparison in what it will deliver. Had one and loved it to the max!
If I remember correctly, and don't hold me too it, I think he already purchased one a while back but then returned it as he found he would have burned it up from the frequent need of backing up his trailer(s). I'm pretty sure I remember reading that Levi said that, but I could be wrong.
Old 07-18-2008 | 05:29 PM
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3.42 Gears

You should still be fine towing if you have a .79 geared G56. I did the swap and with 285's, I still run more RPM's at 70 than the 3.73 rear end 48RE autos. I don't think the swap would be good for towing however with a NV5600, .74 final drive G 56, or auto. You would be lugging the motor towing (anything 5000 plus pounds or over) at under 75 mph. This is from experience. I swapped to 3.42 because I got tired of running 2200 RPM at 70. I normally tow at highway speeds hauling horses to ropings, cattle, tractors, etc. Don't get me wrong, the 3.73 .79 G56 towed like a monster, but just wasn't set up for me driving long stretches of Texas, Colorado, and New Mexico highways at 70 mph. I picked up a couple of hand figured unloaded mpg also. Loaded mpg went up on average 1.5 mpg. Sorry for the long post, but I thought you might want to here from someone who has switched and also uses the truck to tow. I figure Dodge went back to the .74 final gear in 2007 so people would have a true choice. They tried a one size fits all with the .79 & 3.73 rear end and it left people like me that tow on open highways stuck wanting a higher rear end or to go to an auto for the higher final drive.
Old 07-18-2008 | 08:26 PM
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Originally Posted by 92'1stGen
If I remember correctly, and don't hold me too it, I think he already purchased one a while back but then returned it as he found he would have burned it up from the frequent need of backing up his trailer(s). I'm pretty sure I remember reading that Levi said that, but I could be wrong.

You are correct sir


Thanks for the input yall
Old 07-18-2008 | 10:29 PM
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Originally Posted by ronc
1900 @ 65 mph, 2000 @ 70, 2150 @ 75, 2300 @ 80.
Your Mph vs. rpm's are inaccurate,they should be linear. ,from 1900 to 2000 you gained 5 mph,then from 2000 to 2150 you gained 5 mph thats impossible,based on tire size and final drive ratio,each hundred Rpm gain,will gain the same mph.
Old 07-19-2008 | 08:22 AM
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Originally Posted by hammajamma
Your Mph vs. rpm's are inaccurate,they should be linear. ,from 1900 to 2000 you gained 5 mph,then from 2000 to 2150 you gained 5 mph thats impossible,based on tire size and final drive ratio,each hundred Rpm gain,will gain the same mph.
Do you have a 6-speed with 3.42's? I do not know know about the the linear math you are using but my mph and RPM are dead ***** accurate. As for towing with a manual you can always go to fifth gear as oppoosed to sixth.
Old 07-19-2008 | 08:37 AM
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Originally Posted by ronc
Do you have a 6-speed with 3.42's? I do not know know about the the linear math you are using but my mph and RPM are dead ***** accurate. As for towing with a manual you can always go to fifth gear as oppoosed to sixth.
If you were getting 5 mph,per 100 rpm in 6th gear,at 2,000 Rpm you would be running 100 mph.
Old 07-19-2008 | 07:18 PM
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RPM 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear
500 2 4 6 10 13 17
600 3 5 8 11 16 20
700 3 5 9 13 18 23
800 3 6 10 15 21 27
900 4 7 11 17 24 30
1000 4 8 13 19 26 33
1100 5 8 14 21 29 37
1200 5 9 15 23 32 40
1300 5 10 16 25 34 43
1400 6 11 18 27 37 47
1500 6 11 19 29 40 50
1600 7 12 20 31 42 54
1700 7 13 21 33 45 57
1800 8 14 23 34 48 60
1900 8 14 24 36 50 64
2000 8 15 25 38 53 67
2100 9 16 26 40 55 70
2200 9 17 28 42 58 74
2300 10 17 29 44 61 77
2400 10 18 30 46 63 80
2500 11 19 31 48 66 84
2600 11 20 33 50 69 87
2700 11 21 34 52 71 90
2800 12 21 35 54 74 94
2900 12 22 36 56 77 97
3000 13 23 38 57 79 100
3100 13 24 39 59 82 104
3200 13 24 40 61 85 107

Here's a chart based on the G56 and 3.42's as far as mph/rpm.
Old 07-21-2008 | 08:26 AM
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Originally Posted by 92'1stGen
RPM 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear
500 2 4 6 10 13 17
600 3 5 8 11 16 20
700 3 5 9 13 18 23
800 3 6 10 15 21 27
900 4 7 11 17 24 30
1000 4 8 13 19 26 33
1100 5 8 14 21 29 37
1200 5 9 15 23 32 40
1300 5 10 16 25 34 43
1400 6 11 18 27 37 47
1500 6 11 19 29 40 50
1600 7 12 20 31 42 54
1700 7 13 21 33 45 57
1800 8 14 23 34 48 60
1900 8 14 24 36 50 64
2000 8 15 25 38 53 67
2100 9 16 26 40 55 70
2200 9 17 28 42 58 74
2300 10 17 29 44 61 77
2400 10 18 30 46 63 80
2500 11 19 31 48 66 84
2600 11 20 33 50 69 87
2700 11 21 34 52 71 90
2800 12 21 35 54 74 94
2900 12 22 36 56 77 97
3000 13 23 38 57 79 100
3100 13 24 39 59 82 104
3200 13 24 40 61 85 107

Here's a chart based on the G56 and 3.42's as far as mph/rpm.
Thats about right.


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