What gears do I have?

[Flyin Phil]

I am not the original owner of my car and am not sure what gear ratio is installed. Does anyone have speed comparison info available? For instance, 60MPH should be ??? RPMs with 3.07 gears, ??? RPMs with 3.55 gears, ??? RPM with 4.01 gears. I have 17 inch tires.

Thanks in advance.

 

[phiebert]

According to my calculations, this is what the speeds should be...this is based on 25.4 inch diameter of the tires (wheels plus tires) which is apparently the configuration for a Viper with stock tires.


Gear along the top of the chart, RPM along the side, mph in the chart. So for example, at 3000 rpm with stock 3.07's you should be doing 41 mph in 2nd gear. With 3.55's you would be doing 36 mph and with 4.01's you would be doing 32 mph.

3.07 gears (stock)

RPM 1st 2nd 3rd 4th 5th 6th
2000 19 28 38 49 67 98
2250 21 31 43 55 75 111
2500 23 35 47 62 83 123
2750 25 38 52 68 91 135
3000 28 41 57 74 100 148
3250 30 45 62 80 108 160
3500 32 48 66 86 116 172
3750 35 52 71 92 125 185
4000 37 55 76 98 133 197
4250 39 59 80 105 141 209
4500 42 62 85 111 150 222
4750 44 66 90 117 158 234
5000 46 69 95 123 166 246
5250 49 73 99 129 175
5500 51 76 104 135 183
5750 53 80 109 142 191
6000 56 83 114 148 200

3.55 gears (what I have)

RPM 1st 2nd 3rd 4th 5th 6th
2000 16 24 33 43 58 85
2250 18 27 37 48 65 96
2500 20 30 41 53 72 106
2750 22 33 45 59 79 117
3000 24 36 49 64 86 128
3250 26 39 53 69 93 138
3500 28 42 57 74 101 149
3750 30 45 61 80 108 160
4000 32 48 65 85 115 170
4250 34 51 70 90 122 181
4500 36 54 74 96 129 192
4750 38 57 78 101 137 202
5000 40 60 82 106 144 213
5250 42 63 86 112 151 223
5500 44 66 90 117 158 234
5750 46 69 94 122 165 245
6000 48 72 98 128 173

4.01 (A little much for a Viper isn't it?)

RPM 1st 2nd 3rd 4th 5th 6th
2000 14 21 29 38 51 75
2250 16 24 33 42 57 85
2500 18 26 36 47 64 94
2750 19 29 40 52 70 104
3000 21 32 43 57 76 113
3250 23 34 47 61 83 122
3500 25 37 51 66 89 132
3750 27 40 54 71 95 141
4000 28 42 58 75 102 151
4250 30 45 62 80 108 160
4500 32 48 65 85 115 170
4750 34 50 69 90 121 179
5000 35 53 72 94 127 188
5250 37 56 76 99 134 198
5500 39 58 80 104 140 207
5750 41 61 83 108 146 217
6000 43 64 87 113 153 226

 

[onerareviper]

The MPH thing is only right if your speedometer is calibrated properly with an aftermarket calibration box. I think a better way would be to count the rotations of the driveshaft. You need to mark the output shaft and count the rotations per 1 full tire rotation. One full stock tire diameter rotation will equal 3.07 turns on output shaft.

Can someone confirm what I said above? As I am tired, and may be spouting BS.

Later

 

[Flyin Phil]

phiebert, thanks very much for the chart. I will use it to see what I've got. I'll also validate by tire diameter.

onerareviper, thank you, I agree that the most accurate method would be to count revolutions, though I didin't do this as I thought it'd be alot of work getting the car off the ground and getting the engine to turn easily. Probably means removing all of the spark plugs.

I don't believe a speedo calibrator exist in my car, but I could be wrong on that.

 

[phiebert]

If done right, you won't see your calibrator. It is behind the instrument panel up under the dash. It's a little black box (at least in mine) that is about half the size of a computer mouse (closest thing that I could compare it too!).

 

[jcaspar1]

"I agree that the most accurate method would be to count revolutions, though I didin't do this as I thought it'd be alot of work getting the car off the ground and getting the engine to turn easily. Probably means removing all of the spark plugs."

or you could put it in neutral!

 

[joe117]

Neutral get's my vote.

 

[Ulysses]

Put it in neutral, get it off the ground, and count the revolutions.

 

[Flyin Phil]

Thanks, gents. I was thinking about counting revolutions of the engine, but you've pointed out that I need to count revolutions of the driveshaft only. That's easy to do.

 

[Bill 96 GTS]

no need to get it off the ground. Just put in neutral and roll it one tire revolution while you count the driveshaft revolutions. You can do it alone but it is easier with a helper. Push it forward while you watch from the rear. Don't run over your foot while counting.