trying to verify a 280zx transmission ratio question

Engine, Transmission and related drivetrain.
Gereed75
Posts: 7
Joined: 17 Apr 2017 20:53
Location: PA

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 -

1983
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.

So.....it 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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