Both the e3 sedans and the e9 coupes used the same automatic transmissions but they changed during model year production. Initially the ZF 3HP-20 was installed in the early 2500 and 2800 sedans as well as in the 2800CS and later in the 2.5CS.
It was replaced by the similar ZF 3HP-22 in the later 2500 and 2800 and introduced in the US 2800 Bavaria. According to the factory manuals the 2800CS and 2.5CS kept the ZF 3HP-20. The only difference appears to be very slighty different ratios in 1st and 2nd gears and oil cooling lines added in the 3HP-22 to the radiator..
This transmission was replaced by the ZF-BW-65 where the ZF 3HP-22 was used in the sedans starting with the 2800L, 3.0S, 3.0Si, 3.0L, 3.3L for Europe and for the US 3.0 Bavaria, 3.0S and Si. The 3.0CS coupes now received this transmission as well. This likely took place in 1971 as these new models were introduced.
For the purpose of greater clarity, I will refer to the ZF-BW-65 from here on as the BW-65 only.
The gear lever on the ZF transmission is a slender stalk and the BW uses a T handle. However, initial use of the BW still utilized the ZF shift stalk up until coupes 2230960 and 2250188 (May 1972) and sedans 2800 2400835, 3.0 3152301 and 3.0 Bavaria 3131841. The lower vertical and horizontal shift linkage rods are different to match the appropriate lever. I believe this change was driven by DOT requirements for a positive lockout from Reverse to Drive as the early shifter only has a spring loaded detent.
The ZF uses Dexron fluid while the BW uses Ford Type F and they are not interchangeable. Both have dipsticks on the passenger or right side of the engine bay, the only difference being that the ZF dipstick tube rises from the transmission housing itself and the BW comes forward from the oil pan. Also, they utilize different speedometer drive assemblys, the ZF is metal and the BW is plastic with an internal metal bushing. Speedometer cables are identical. The ZF o-ring seal is 18 x 2.0mm or 19 x 1.8mm and the BW uses a 19 x 1.8mm seal with an internal 8 x 15 x 5mm bushing/seal. BMW will sell you a 18 x 2.4mm o-ring which does NOT fit, you can find o-rings online.
As a side note, the e12 sedans used the BW through 1976 and reverted to the ZF HP-22 in 1977. They were introduced in Europe in 1972 but the ZF dipstick is on the driver or left side of the engine bay likely due to interference with log plenum on the M30 injected sixes.
The 2002 used a ZF transmission but only the ZF 3HP-12, which is shorter than the 3HP-22, and the dipstick is still on the passenger side of the engine bay.
The easiest way to tell a ZF from the BW is the driver side of the housing and the dipstick tube exit from the transmission.
ZF 3HP20/22
BW-65
ZF 3HP-20/22
2800CS ZF and early 3.0CS BW shift handle
Later 3.0CS BW shift handle
Comparison
ZF speedometer drive, same as ZF 4 speed manual
BW speedometer drive showing internal metal bushing and seal
It was replaced by the similar ZF 3HP-22 in the later 2500 and 2800 and introduced in the US 2800 Bavaria. According to the factory manuals the 2800CS and 2.5CS kept the ZF 3HP-20. The only difference appears to be very slighty different ratios in 1st and 2nd gears and oil cooling lines added in the 3HP-22 to the radiator..
This transmission was replaced by the ZF-BW-65 where the ZF 3HP-22 was used in the sedans starting with the 2800L, 3.0S, 3.0Si, 3.0L, 3.3L for Europe and for the US 3.0 Bavaria, 3.0S and Si. The 3.0CS coupes now received this transmission as well. This likely took place in 1971 as these new models were introduced.
For the purpose of greater clarity, I will refer to the ZF-BW-65 from here on as the BW-65 only.
The gear lever on the ZF transmission is a slender stalk and the BW uses a T handle. However, initial use of the BW still utilized the ZF shift stalk up until coupes 2230960 and 2250188 (May 1972) and sedans 2800 2400835, 3.0 3152301 and 3.0 Bavaria 3131841. The lower vertical and horizontal shift linkage rods are different to match the appropriate lever. I believe this change was driven by DOT requirements for a positive lockout from Reverse to Drive as the early shifter only has a spring loaded detent.
The ZF uses Dexron fluid while the BW uses Ford Type F and they are not interchangeable. Both have dipsticks on the passenger or right side of the engine bay, the only difference being that the ZF dipstick tube rises from the transmission housing itself and the BW comes forward from the oil pan. Also, they utilize different speedometer drive assemblys, the ZF is metal and the BW is plastic with an internal metal bushing. Speedometer cables are identical. The ZF o-ring seal is 18 x 2.0mm or 19 x 1.8mm and the BW uses a 19 x 1.8mm seal with an internal 8 x 15 x 5mm bushing/seal. BMW will sell you a 18 x 2.4mm o-ring which does NOT fit, you can find o-rings online.
As a side note, the e12 sedans used the BW through 1976 and reverted to the ZF HP-22 in 1977. They were introduced in Europe in 1972 but the ZF dipstick is on the driver or left side of the engine bay likely due to interference with log plenum on the M30 injected sixes.
The 2002 used a ZF transmission but only the ZF 3HP-12, which is shorter than the 3HP-22, and the dipstick is still on the passenger side of the engine bay.
The easiest way to tell a ZF from the BW is the driver side of the housing and the dipstick tube exit from the transmission.
ZF 3HP20/22
BW-65
ZF 3HP-20/22
2800CS ZF and early 3.0CS BW shift handle
Later 3.0CS BW shift handle
Comparison
ZF speedometer drive, same as ZF 4 speed manual
BW speedometer drive showing internal metal bushing and seal
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Numbers make sense, my VIN is 2250122 and is equipped with "slender" shift handle. I do recognize some amazing photography! Great work. These questions about the autos do come up from time to time, as you know, and this will help fill in some blanks. Good job!