Fortuna Wolf
Veteran Member
I have experimentally determined that my combination ratio for my 01m transmission is 2.53 give or take a few percent. Next time my engine is hot I'll see if I can get a graph with vag-com of my transmission and engine rpm and get a more accurate number.
I used the numbers 23.5" tire circumference, 2900 rpm, 80 mph (just from memory, but reality is very close to that).
Now scanning through the great red book (the Bentley) it tells me that all TDIs have 3.700 and 3.273 final drive ratios, and 4th gear ratios of .742. Some other engines were given transmissions with a 4.875 final drive ratio and .679 4th gear.
3.7*.679 = 2.51 combination ratio, which is closest to the number I got
But there is no transmission with that particular combination listed.
The TDI's lowest combination gear ratio is 3.273 * .742 = 2.43.
Now, the paper tag on my transmission is pretty much faded and chewed up and I can't read my transmission code (I'll try again tomorrow). Otherwise I'll get vag-com out and try to get a more precise reading of my gear ratio.
I was just thinking... the lowest possible gear ratio would combine the 3.273 final drive with a .679 4th gear for a combined gear ratio of 2.22. That would be 2,222 rpm at 70 mph. Not bad
Granted, if we had an 09A transmission we could have a final gear ratio of 1.86, but that's another story
Anyhow, if anyone knows a bit more about these transmissions than I, is it possible to swap gears and differentials? Can I order just the gear or differential? This is mostly a thought experiment BTW. I freely admit it doesn't make any sort of financial sense to swap out the gears on my transmission.
PS: I just realized that I should include the TC's gear ratio in too. Its .978 I believe. Not going to edit everything right now because it doesn't really matter (comparisons are the same)
I used the numbers 23.5" tire circumference, 2900 rpm, 80 mph (just from memory, but reality is very close to that).
Now scanning through the great red book (the Bentley) it tells me that all TDIs have 3.700 and 3.273 final drive ratios, and 4th gear ratios of .742. Some other engines were given transmissions with a 4.875 final drive ratio and .679 4th gear.
3.7*.679 = 2.51 combination ratio, which is closest to the number I got
But there is no transmission with that particular combination listed.
The TDI's lowest combination gear ratio is 3.273 * .742 = 2.43.
Now, the paper tag on my transmission is pretty much faded and chewed up and I can't read my transmission code (I'll try again tomorrow). Otherwise I'll get vag-com out and try to get a more precise reading of my gear ratio.
I was just thinking... the lowest possible gear ratio would combine the 3.273 final drive with a .679 4th gear for a combined gear ratio of 2.22. That would be 2,222 rpm at 70 mph. Not bad
Granted, if we had an 09A transmission we could have a final gear ratio of 1.86, but that's another story
Anyhow, if anyone knows a bit more about these transmissions than I, is it possible to swap gears and differentials? Can I order just the gear or differential? This is mostly a thought experiment BTW. I freely admit it doesn't make any sort of financial sense to swap out the gears on my transmission.
PS: I just realized that I should include the TC's gear ratio in too. Its .978 I believe. Not going to edit everything right now because it doesn't really matter (comparisons are the same)
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