2007 3/4ton gears

[CBrahs]

I have looked at several places but can not find any gears for my new truck. It has 37in tires with auto transmission and need to find a 4. 30'ish gear for front and rear of truck. Does anyone have a line on gears. Has 11. 5 rear aam axles. I think the front is 9. 25 but not totally sure.

 

[Bob4x4]

I think you might have better luck finding 4. 56's



Bob

 

[CBrahs]

I thought of that but do you think my RPM's will be too high going down the freeway? I would still like to get some MPG out of it.

 

[oneshotkyle]

even with my 35's and 3. 73 gears i'm at 2000 rpm at 70. depends on the kind of driving you will most likely be doing and the state hwy speed in NM. in my opinion 4. 10's would be my choice for 37's.

 

[Bob4x4]

even with my 35's and 3. 73 gears i'm at 2000 rpm at 70. depends on the kind of driving you will most likely be doing and the state hwy speed in NM. in my opinion 4. 10's would be my choice for 37's.

The autos have a higher od than your 6spd. Mine is about 2krpm at 70 with 35's and 4'10s.



Bob

 

[CBrahs]

I found Klenger's gear ratio/tire size chart and played with it for a bit. If I did it correctly w/ 3. 73, and 37in tires @ 1700 RPM in overdrive I am doing 73MPH and with 4. 10 gears, 1700 RPM would be doing 66MPH. 4. 10's might be where I need to be but to bring it down to the original gear (37's vs 265x70x17's) I would need to go to 4. 34 gears. I am affraid that 4. 56's will be too much. Maybe I am just being a pain in the hind end, I just don't want to burn up the transmission when I am pulling a trailer. Looking at buying a boat when I sell my 5th wheel.



3. 73's

47RE/48RE 4 Speed Automatic

Gear 1 2 3 4

RPM 2. 450 1. 450 1. 000 0. 690

1000 12 20 30 43

1100 13 22 32 47

1200 14 24 35 51

1300 16 26 38 56

1400 17 28 41 60

1500 18 31 44 64

1600 19 33 47 68

1700 20 35 50 73

1800 22 37 53 77

1900 23 39 56 81

2000 24 41 59 86

2100 25 43 62 90

2200 26 45 65 94

2300 28 47 68 98

2400 29 49 71 103

2500 30 51 74 107

2600 31 53 77 111

2700 33 55 80 115

2800 34 57 83 120

2900 35 59 86 124

3000 36 61 89 128

3100 37 63 91 133

3200 39 65 94 137

3300 40 67 97 141



4. 10's

47RE/48RE 4 Speed Automatic

Gear 1 2 3 4

RPM 2. 450 1. 450 1. 000 0. 690

1000 11 19 27 39

1100 12 20 30 43

1200 13 22 32 47

1300 14 24 35 51

1400 15 26 38 54

1500 16 28 40 58

1600 18 30 43 62

1700 19 31 46 66

1800 20 33 48 70

1900 21 35 51 74

2000 22 37 54 78

2100 23 39 56 82

2200 24 41 59 86

2300 25 43 62 89

2400 26 44 64 93

2500 27 46 67 97

2600 28 48 70 101

2700 30 50 72 105

2800 31 52 75 109

2900 32 54 78 113

3000 33 56 81 117

3100 34 57 83 121

3200 35 59 86 125

3300 36 61 89 128

 

[oneshotkyle]

for example: 37 inch tall tires aren't truley 37" my 35inch toyo m/t are 34 somethin. so that adds to the final ratio also...

 

[Bob4x4]

37x1350x17's are 37. 1" tall... ... ..... http://www.toyo.com/docs/tires/product_spec.asp?lpid=18136&name=Open Country M/T™&category=off-road



Bob

 

[oneshotkyle]

hey bob don't want a ******* match. but if you mount that tire on a 8 inch rim maybe, then put it on a nine inch rim, then ten. does the tire still have the same height? how about running 35lbs of air versus the 65lbs max. just from my experience there is to many variable's in tire height.

 

[Bob4x4]

No match intended but the Toyos are pretty much what they say they are and . 1-. 2 doesnt amount to a hill of beans. :-laf :-laf



Bob

 

[HLewallen]

And I don't mean to nit pick either . . . but what you actually want to look at is static loaded radius or something like that. The tire is probably only 37. 1 inches tall on the specified rim unloaded - the radius (which is really incorrect at this point) is different from center to top and center to ground.

 

[CBrahs]

I looked at Pro Comp website and they claim the 37x13. 5x20 tires which i have have an overall height of 36. 8 inches.

 

[Jason Hughes]

4. 30's do not exist for these trucks. If you have 37 inch tires, 4. 10's work pretty well according to customer feedbacks. I would only suggest 4. 56's if you tow heavy loads all the time and your speeds are 50-65mph on the highway. And yes the diesels have a aam 11. 5 rear-end and a aam 9. 25 reverse rotation diff in front.

 

[CBrahs]

THe more I am reading on here from your advise the more I am going to go with 4. 10's. Anyone have a good source for those gears?