it was very random
every 80s truck i have ever parted with the 400 trans in it was always the short tail
overal trans length including the output yoke(bolt on style) is always the same 31.5" as the 9" tail th350
its crazy like that
the old long tail th400 were way long time ago in the big cars
not common at all anymore
this goes for regular 3L80/th400 only and only 4x2 version
not for the 3L80HD or any other 400 variants
4x4 was a whole different tailshaft than 4x2
the 3L80HD started in 87 and up in the trucks and was 34.5" long overall
and had the 27 spline output like a th350 and 700r4 and so on
tag code LJA and HD cast on the case at the bellhousing top side
i own one and have seen two so far
it is complicated
i have found that the charts and info online that show lengths of GM trannies that are often 1" incorrect
i dont know why
when you put a tape measure on the actual trannies and measure them they are actually 1" longer than stated online
375 and 375B were combinations of the th350 and the th400,
one was a 400 case and the other was a 350 case
th375:
http://en.wikipedia.org/wiki/Turbo-H...Hydramatic_375
http://en.wikipedia.org/wiki/Turbo-H...L80_.2F_3L80HD