trying to verify a 280zx transmission ratio question

Engine, Transmission and related drivetrain.
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trying to verify a 280zx transmission ratio question

Postby Gereed75 » 01 Aug 2017 06:26

I am replacing the stock 4 speed in my 72 510 race car.

After searching every conceivable thread on all the nooks and crannies on the net, I decided that the "Close ratio" 280ZX box was the best choice. I found a really nice looking 82 and bought it. I have verified that the ratios match the FSM for a "close ratio" box - 3.062/1.858/1.308/1/.745.

Next, following all of the vintage net wisdom, I tracked down a 32310-58S54 OD gearset (NOS still in the box!!) with the expectation that this would yield the road race perfect .864 OD ratio. This gear set is definitely 22/37. Oh boy - well on my way to faster lap times and the trick set up!!

Then I found this spreadsheet in a thread on another site -

Main C/G Ratio
23 29 0.793103448
1 34 14 3.062111801
2 28 19 1.85812357
3 28 27 1.307568438
4 1 1 1
5 26 44 0.745059289

I have confirmed that all of the tooth counts in this spreadsheet match the FSM and the ratios in my box.

When you plug in the magic 22/37 numbers into fifth - you get the same old .745 OD ratio, not the .864 that me (and every road racer) wants. appears that all of the old net wisdom was wrong. The 32310-58S54 gearset does not yield an .864 OD in this tranny. It is possible that this 22/37 gearset got switched into the wrong box and the 32310 gearset is some other ratio, but that seems highly unlikely and there is no evidence of a different fifth gearset that actually yields .864 anywhere on the net.

So before I punt the whole thing, does any one see an error in the spreadsheet, the method, or my ability to count teeth on a gearset??

I know that you can change the main ratios with some other boxes and get a hybrid .709 "main" ratio and yes, you will get a .864 OD, but in the process, you lose the desiriable 1.858 "close" second. It looks much easier to just get an 86 200sx box, swap bell housings with an L box and get 3.321/1.9/1.308/1/.833

Guru's please confirm!!

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