Folks,

The article below was just published in the NCRS publication "The Corvette Restorer" (Vol 32 Number 1 Summer 2005). Figured someone out there would need it when building a C3 "street" machine. Enjoy.

4.11s the Other Way

by DAN PYZEL
How many times have you heard it said: "Man, all this car needs is a 4.11 gear!" Right, but most of us also know by now that in a car with 4.11 s, the motor gets awfully busy at today's interstate speeds. What if I told you that you could have your cake and eat it too? This all has to do with different rear end gears and different transmission ratios.

Chevrolet offered two different transmission ratio sets for most 4-speed Corvettes, the close-ratio and the wide-ratio. Also offered were a range of rear end ratios to suit the needs of most buyers, from 2.73 to 4.56. Not all possible combinations of transmission and rear end ratios were available together. For example, the wide-ratio transmission was not available with a 3.70,4.11, or 4.56 rear end gear. Solid lifter engines were generally available only with close-ratio transmission, no matter what the rear end gear ratio was. Chevrolet Engineering set these rules according to the maximum torque load they felt the gears in the transmission could handle.

So what are a close-ratio and a wide-ratio? During the years of Corvette production, there were slight differences, but for example, in 1963 cars, a close-ratio had a gear reduction of 2.20 in first, 1.64 in second, 1.31 in third, and of course 1:1 or direct in fourth. The wide-ratio had 2.54 in first, 1.89 in second, 1.51 in third, and again 1:1 in fourth. These numbers don't seem very different, but what really counts is the overall reduction, which is the ratio of any of these numbers multiplied by the differential ratio. Lets multiply some of them out and see what we come up with.

3.36 with close-ratio:     3.36 with wide-ratio:
1- 2.20 x 3.36 = 7.392     1- 2.54 x 3.36 = 8.534
2- 1.64 x 3.36 = 5.510     2- 1.89 x 3.36 = 6.350
3- 1.31 x 3.36 = 4.402     3- 1.51 x 3.36 = 5.073
4- 1.00 x 3.36 = 3.36     4- 1.00 x 3.36 = 3.36

3.55 with close-ratio: 3.55 with wide-ratio:

1- 2.20 x 3.55 = 7.810 1- 2.54 x 3.55 = 9.017
2- 1.64 x 3.55 = 5.822 2- 1.89 x 3.55 = 6.709
3- 1.31 x 3.55 = 4.651 3- 1.51 x 3.55 = 5.360
4- 1.00 x 3.55 = 3.55   4- 1.00 x 3.55 = 3.55

3.70 with close-ratio: 3.70 with wide-ratio:
                          (not offered by GM)
1- 2.20 x 3.70 = 8.140 1- 2.54 x 3.70 = 9.398
2- 1.64 x 3.70 = 6.068 2- 1.89 x 3.70 = 6.993
3- 1.31 x 3.70 = 4.847 3- 1.51 x 3.70 = 5.587
4- 1.00 x 3.70 = 3.70   4- 1.00 x 3.70 = 3.70

4.11 with close-ratio: 4.11 with wide-ratio:
                          (not offered by GM)

1- 2.20 x 4.11 = 9.042 1- 2.54 x 4.11 = 10.439
2- 1.64 x 4.11 = 6.740 2- 1.89 x 4.11 = 7.768
3- 1.31 x 4.11 = 5.384 3- 1.51 x 4.11 = 6.206
4- 1.00 x 4.11 = 4.11   4- 1.00 x 4.11 = 4.11

As the numbers go up with the lower ratio rear end gears (higher numerically), the overall reduction increases in kind. The point of this article is to note the overall reductions of the various combinations. If one were to replace a close-ratio transmission with a wide-ratio transmission, the effect would be to lower the rear-end ratio by two steps in first, second and third gears without changing the fourth-gear ratio. For example; the overall reduction numbers of a 3.36 gear with a wide¬ratio transmission are very close to those of a 3.70 gear with a close-ratio transmission in first, second and third, but still a 3.36 in fourth. Similarly, a wide ratio with a 3.55 gear has almost exactly the same overall reductions in first second and third as a 4.11 with a close-ratio transmission, but again retains the 3.55 in fourth. A 3.70 gear with a wide-ratio transmission would be almost like 4.56's in first, second and third, and so on. A close-ratio transmission is desirable in racing in order to keep the engine rpm near maximum power at various speeds, but that's not so important for driving and cruising. So there's an easy alternative if you want plenty of acceleration around town, but still desire a satisfactory cruising gear for the highway.

Dan Pyzel
bndpyzel@yahoo.com Membership #7114
This article was submitted in furtherance of the requirements for the Founders' Award.

All very true.  But it leaves out an important consideration.  Fourth gear is a 1:1 in both cases, and the rear axle ratio will have the same affect on the highway.  The rear ratio will determine the engine RPM at highway speeds.

Still, the effects in 1st, 2nd, and 3rd gears is accurate, and should be considered when selecting the final drive ratio.

If you wanted to go 4-speed auto the ratios are:
   200-4R        700R4/4L60E    4L80E/4L85E
1 2.78        3.06           2.48
2 1.57        1.63          1.48
3 1.00        1.00          1.00
4 0.67        0.70          0.75
custom7638556.5610416667

I have a 3.36 rear gear and a Tremec TKO 5 speed in mine. Makes for a great cruiser with plenty of out of the hole grunt.
1st 3.27
2nd 1.98
3rd 1.34
4th 1.0
5th .68

[QUOTE=Eddie 70] I have a 3.36 rear gear and a Tremec TKO 5 speed in mine. Makes for a great cruiser with plenty of out of the hole grunt.
1st 3.27
2nd 1.98
3rd 1.34
4th 1.0
5th .68

[/QUOTE]

Seems to me that is the best of both worlds; fast off the line and easy engine RPM on the interstate.

An overdrive and a bit steeper rear gear is always a nice combination.  There are still some considerations.  I would like to use an overdrive and a 3.55, but that's a LONG way off.