Bit of a weird question, but it's what I'm faced with. Is there a systematic way to determine the ratios in an 020 without opening the box? The box is in use in my rally car, and has good ratios for what I do, problem is that when it was built, they took off the model number and re-stamped it with just the final drive ratio. I'd like to figure out what it was originally, and if they changed any of the ratios when built. Trying to get my head around the math and a way to break it down. Thanks bo
It can be done, either with the car running.... or with the gearbox out of the car... While the car drives : drive the car in each gear at a fix RPM point, say 4000 or 5000 rpm, and see what speed you do Best use GPS speed as that is more accurate There are a few things we can say we know.... 1 st gear is always 3,45 by VW ( unless its a special close ratio gearset ) 2 nd gear is either 1.94 or 2.12 by VW With the above info and the circumference of the tyres you can find out the Final Drive ratio Take 3th 1,44 / 4 th 1.13 and 5 th 0,91 as starting point Play a bit with a calculation program ( as below) and see if 1 st and 2 nd gear make sense about rpm and speed and rpm drop after gear change https://www.bacciromano.com/en/prod...6gyC8satqz6SaFXBqkaYVllP4dETJVhXYUEueX3CKAenA http://www.brokevw.com/020ratios.html
Had to pull it before I could do a proper speed test (seal leak, clutch not liking it). I figured I could just manually clock the input shaft to the output and calculate the ratios. Taped a couple of degree wheels to in and out and started taking notes... Turns out I'm still too dense to figure out an answer. If I understand correctly, 1st should be 3.445 and reverse should have a 3.167. In 1st, I can turn the clutch around 16.6 turns for 1 on the axle. Reverse about 15.2 turns. My math is putting me somewhere between 4.6 - 4.8 for the final, and there's no way I have a VWMS ring in there. I will say that tach'd right out around 6k, I'm only able to get a bit over 90 mph with 73.75" circumference tires. I just found a video that showed 52.9 mph (gps) at 3300rpm. Just for completeness, my measurements input to output (so gear and final): 1st: 16.57 2nd: 10.71 3rd: 6.97 4th: 5.45 5th: 4.35 The new stamp on the case shows 3.89, but it doesn't add up. The box is getting to the point it needs to be rebuilt, as the 3-4 syncros are getting lazy, but I'm trying to determine a good replacement before I take it out of service. It is in a rally car, so I'm kind of fond of the spacing, I just need a touch more final ratio. If any of you can see the obvious that I'm missing, I'd love to hear about it.
More Excel.... 52.9 mph= .8816 mile/min= 4655.2 ft/min= 55862.4 in/min= divided by 73.75" (tire) = 757 wheel rpm @3300= 4.36 final total ratio.
