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71B identification


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#1 theremm

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Posted 13 November 2014 - 07:47 AM

Is it possible to identify the ratios of a 71B gearbox (from a Z) by casting numbers without inspecting the internals and with no prior knowledge of the history of the box?I want to convert my auto 240z to a 5spd and am particularly after a 71B with a 2.9 first. I understand the 71B's had a variety of ratios over the years across different models of the 240/260. Hoping to avoid the frustration of purchasing the wrong box in situations where sellers are unsure which year of car the gearbox was taken from. Cheers

Alexander
1973 240z

#2 dat2kman

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Posted 13 November 2014 - 09:32 AM

Hi Alexander,
Unfortunately, No, we cant tell by looking.
If it is out of car sitting on ground , bestest way is, fit an old clutch plate, with a white reference paint mark at a point, make a mark near on bell.
Rotate plate 3 times, while box in first gear.
The hard bit is, after a little dob of white penpaint mark on the bit of output, on one spline only,
You need to see if it rotates almost one turn, or goes past one turn.
Ie 3 turns in, in first gear, almost, or past, one turn out,
Will denote either a 2.9 first, or, a 3.3 first.
The 2.9 is the better box, after rebuild if reqd.
Majority of 2.9 boxes had the filler plug on other side, but bells can be swapped, i dont go on that.
Fitted to some 260z, both 2 and 4 seaters.
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#3 theremm

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Posted 13 November 2014 - 10:43 AM

Thanks Jason




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