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Discussion Starter #1
I was thinking of switching to 3.73 gears, but I had some questions for those that have done this or are familiar with it:

1) How bad does it affect your gas mileage? My Bullitt is a daily driver (though because of my commute that amounts to about 2000 miles per year).

2) How drastic is the difference in RPM's? I had a car before that was geared high and it was annoying how many RPM's it would turn going down the interstate.

3) Is there a table out there that compares the RPMs with stock gearing versus the RPM's with 3.73's?

4) How much time will it really shave off of the quarter mile? (Right now I am bone stock)

5) Can I change them myself in my garage without unusual tools? How long does it take?

6) How do I get my speedometer calibrated to reflect the change in gears?
 

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1) How bad does it affect your gas mileage? My Bullitt is a daily driver (though because of my commute that amounts to about 2000 miles per year).

Did not seem to have much of a noticeable affect

2) How drastic is the difference in RPM's? I had a car before that was geared high and it was annoying how many RPM's it would turn going down the interstate.

There is a definite change but it is not really all that drastic compared to the stock set.

3) Is there a table out there that compares the RPMs with stock gearing versus the RPM's with 3.73's?

Stock

<TABLE class=whs4 width=500 border=4 x-use-null-cells><TBODY><TR class=whs5 bgColor=#c0ffff><TD>RPM's</TD><TD>1000</TD><TD>2000</TD><TD>3000</TD><TD>4000</TD><TD>5000</TD><TD>6000</TD></TR><TR><TD class=whs6 bgColor=#c0ffc0>1st</TD><TD>6.91</TD><TD>13.83</TD><TD>20.74</TD><TD>27.66</TD><TD>34.57</TD><TD>41.49</TD></TR><TR><TD class=whs7 bgColor=#80ff80>2nd</TD><TD>11.69</TD><TD>23.37</TD><TD>35.06</TD><TD>46.75</TD><TD>58.43</TD><TD>70.12</TD></TR><TR><TD class=whs8 bgColor=#40ff40>3rd</TD><TD>17.71</TD><TD>35.41</TD><TD>53.12</TD><TD>70.83</TD><TD>88.53</TD><TD>106.24</TD></TR><TR><TD class=whs9 bgColor=#00c000>4th</TD><TD>23.37</TD><TD>46.75</TD><TD>70.12</TD><TD>93.49</TD><TD>116.86</TD><TD>140.24</TD></TR><TR><TD class=whs10 bgColor=#008000>5th</TD><TD>34.88</TD><TD>69.77</TD><TD>104.65</TD><TD>139.54</TD><TD>174.42</TD><TD>209.31</TD></TR></TBODY></TABLE>

3.73 ranges
MPH <TABLE class=whs4 width=500 border=4 x-use-null-cells><TBODY><TR class=whs5 bgColor=#c0ffff><TD>RPM's</TD><TD>1000</TD><TD>2000</TD><TD>3000</TD><TD>4000</TD><TD>5000</TD><TD>6000</TD></TR><TR><TD class=whs6 bgColor=#c0ffc0>1st</TD><TD>6.06</TD><TD>12.12</TD><TD>18.19</TD><TD>24.25</TD><TD>30.31</TD><TD>36.37</TD></TR><TR><TD class=whs7 bgColor=#80ff80>2nd</TD><TD>10.25</TD><TD>20.49</TD><TD>30.74</TD><TD>40.98</TD><TD>51.23</TD><TD>61.47</TD></TR><TR><TD class=whs8 bgColor=#40ff40>3rd</TD><TD>15.52</TD><TD>31.05</TD><TD>46.57</TD><TD>62.09</TD><TD>77.61</TD><TD>93.14</TD></TR><TR><TD class=whs9 bgColor=#00c000>4th</TD><TD>20.49</TD><TD>40.98</TD><TD>61.47</TD><TD>81.96</TD><TD>102.45</TD><TD>122.94</TD></TR><TR><TD class=whs10 bgColor=#008000>5th</TD><TD>30.58</TD><TD>61.16</TD><TD>91.75</TD><TD>122.33</TD><TD>152.91</TD><TD>183.49</TD></TR></TBODY></TABLE>

4) How much time will it really shave off of the quarter mile? (Right now I am bone stock)

5) Can I change them myself in my garage without unusual tools? How long does it take?

You can do that but I chose to have a garage change mine to ensure that there would not be any problems.

6) How do I get my speedometer calibrated to reflect the change in gears?

I bought a speedcal for mine

Other than that it was by far one of the best mods I have done to date your going to be very happy with them. The kick in the pants this car needs.
 

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Hey Mustangwi,
Talk about instant and complete information!

I will have to concur that the mileage was not affected at all even on a 1300 mile trip from Michigan to Florida. Of course, with the additional ZOOM factor, your mileage could take a dive. The 373 gears certainly wake up a stock Bullitt.

As far as changing the gears yourself, I watched it done and there is a lot to it. My techs used a dial gage to set the ring gear if I recall correctly. The job required pulling the brakes and the axles on both sides. It took four hours for techs who had done the same exact job many times before on SN95 Mustang GTs. (MRT)
 

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Discussion Starter #4
mustangwi said:
1) How bad does it affect your gas mileage? My Bullitt is a daily driver (though because of my commute that amounts to about 2000 miles per year).

Did not seem to have much of a noticeable affect

2) How drastic is the difference in RPM's? I had a car before that was geared high and it was annoying how many RPM's it would turn going down the interstate.

There is a definite change but it is not really all that drastic compared to the stock set.

3) Is there a table out there that compares the RPMs with stock gearing versus the RPM's with 3.73's?

Stock

<TABLE class=whs4 width=500 border=4 x-use-null-cells><TBODY><TR class=whs5 bgColor=#c0ffff><TD>RPM's</TD><TD>1000</TD><TD>2000</TD><TD>3000</TD><TD>4000</TD><TD>5000</TD><TD>6000</TD></TR><TR><TD class=whs6 bgColor=#c0ffc0>1st</TD><TD>6.91</TD><TD>13.83</TD><TD>20.74</TD><TD>27.66</TD><TD>34.57</TD><TD>41.49</TD></TR><TR><TD class=whs7 bgColor=#80ff80>2nd</TD><TD>11.69</TD><TD>23.37</TD><TD>35.06</TD><TD>46.75</TD><TD>58.43</TD><TD>70.12</TD></TR><TR><TD class=whs8 bgColor=#40ff40>3rd</TD><TD>17.71</TD><TD>35.41</TD><TD>53.12</TD><TD>70.83</TD><TD>88.53</TD><TD>106.24</TD></TR><TR><TD class=whs9 bgColor=#00c000>4th</TD><TD>23.37</TD><TD>46.75</TD><TD>70.12</TD><TD>93.49</TD><TD>116.86</TD><TD>140.24</TD></TR><TR><TD class=whs10 bgColor=#008000>5th</TD><TD>34.88</TD><TD>69.77</TD><TD>104.65</TD><TD>139.54</TD><TD>174.42</TD><TD>209.31</TD></TR></TBODY></TABLE>

3.73 ranges
MPH <TABLE class=whs4 width=500 border=4 x-use-null-cells><TBODY><TR class=whs5 bgColor=#c0ffff><TD>RPM's</TD><TD>1000</TD><TD>2000</TD><TD>3000</TD><TD>4000</TD><TD>5000</TD><TD>6000</TD></TR><TR><TD class=whs6 bgColor=#c0ffc0>1st</TD><TD>6.06</TD><TD>12.12</TD><TD>18.19</TD><TD>24.25</TD><TD>30.31</TD><TD>36.37</TD></TR><TR><TD class=whs7 bgColor=#80ff80>2nd</TD><TD>10.25</TD><TD>20.49</TD><TD>30.74</TD><TD>40.98</TD><TD>51.23</TD><TD>61.47</TD></TR><TR><TD class=whs8 bgColor=#40ff40>3rd</TD><TD>15.52</TD><TD>31.05</TD><TD>46.57</TD><TD>62.09</TD><TD>77.61</TD><TD>93.14</TD></TR><TR><TD class=whs9 bgColor=#00c000>4th</TD><TD>20.49</TD><TD>40.98</TD><TD>61.47</TD><TD>81.96</TD><TD>102.45</TD><TD>122.94</TD></TR><TR><TD class=whs10 bgColor=#008000>5th</TD><TD>30.58</TD><TD>61.16</TD><TD>91.75</TD><TD>122.33</TD><TD>152.91</TD><TD>183.49</TD></TR></TBODY></TABLE>

4) How much time will it really shave off of the quarter mile? (Right now I am bone stock)

5) Can I change them myself in my garage without unusual tools? How long does it take?

You can do that but I chose to have a garage change mine to ensure that there would not be any problems.

6) How do I get my speedometer calibrated to reflect the change in gears?

I bought a speedcal for mine

Other than that it was by far one of the best mods I have done to date your going to be very happy with them. The kick in the pants this car needs.
\

Thanks .... any ideas on Question 4??
 

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Yeah, gears are not to be handled by an amateur. You need to know how to adjust backlash and pinion depth, and even then, it's not fun. Most shops charge around $300 for install.
 

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Well 373s certainly make a difference on a road course.

But I am not a drag racer and don't speed shift the Tremec.

What do you think, guys, would 373s get you well into the 13s? (with good driving skills)
 

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Professor Bullitt said:
\

Thanks .... any ideas on Question 4??
This is a tough question to answer, with no real definite answer. Once you get used to running the car with the new gears, you could probably count on .2 to .35 second reduction in 1/4 mile times. The first few runs with gears for a lot of people are discouraging. There is a little bit of a learning curve there.
 

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I doubt he would hit 13's with just a 3.73. Maybe if he pulled out ALOT of weight. 4.10's are a better choice in my opinion. If I had to do it again...I would go 4.30.LOL!
 

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Check the Bullitt Archives at top of page for gear-rpm-speed tables.
 

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Professor Bullitt said:
\

Thanks .... any ideas on Question 4??
Slow day today Rick, nothing but time to kill.

As far as question 4 goes I do not have an answer to that I was running low 14's with the stock gears and the way te car feels now I would think that it may be in the upper 13's but I do not have a definite answer as I never did make it to the track last year. I will agree it does take some getting used to after the stock gears have been replaced. Like I said you are going to love the new gears. The 4.10's are a good way to go but you will experience higher revs on the freeway, not terrible, but it will be noticeable. I have driven a Bullitt both ways and if you are looking for a daily commuter and still have fun on the weekends the 3.73's are a nice set up.

Enjoy!!!


Jeff
 

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i think with gears and tires a bullitt should be mid to low 13's. i know of a guy all stock with drag radials runnin 13.6's or .5's.... who is it that has a 13.8 at 101 posted in thier sig that posts on here.
 

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Discussion Starter #13
That's weird. The slowest time I've seen in a car magazine for a Bullitt is a 14.1 and one magazine got a 13.62 out of a stock Bullitt in a shootout against a Cobra & a Mach 1.
 

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Did you check Time Slips at top of page for some times? When you click on the names there is some info about the car.
 
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