Let's talk Transmissions

[eschaider]

Originally Posted by fastd

My ideal is to set up the gearing so that you could get to 50 mph in first gear at say 5000 rpm (my engine tops out around 6300). In top gear you’d like to be around 2000 rpm at 80 or so.

Check out the Second Strike Gearing Calculator <= clickable. If you use a 0.82 OD TKO 600, a tall 275 x 65 x 15 rear tire (30 inch diameter) you will only be able to get to 69 MPH at 2000 rpm w/ a 2.92 R&P. 80 mph is measurably higher and louder. If you use a more traditional 295 x 50 x 15 tire 2000 rpm will only be 64 MPH! 80 mph with this tire is 2500 rpm.

Don't forget your side pipe exit is only about 24 inches from your left ear. If you are driving on the highway this would be an example of an uncomfortable experience. Ear plugs would help but a lower engine rpm by about six to eight hundred rpm or so would be much better.

A T-56 with a 2.66 first gear will give you approximately a 1700 rpm engine speed at 80 mph. Sound pressure on your eardrum at 2000+ engine rpm for an extended highway drive will diminish your hearing both immediately after the ride and longer term also, not to mention the potential for tinnitus.

The question for the owner / builder is how much pain do you want to associate with the driving of your car. After a while you will be wondering why you didn't think far enough ahead to get under car exhausts.


Ed