New Pistons are NLA. This will only work if you have a piston with the wide seal around the outside edge. Inspect you B2 BEFORE ordering
Since new B2 pistons are no longer being made, repairing your old one is your only option. The very early version with the narrow sealing ring on the outside of the piston is not repairable. You piston MUST have the wide ring as shown.
722.3 B2 Piston Repair Kit
$69.95
SKU:
TRS-7223B2REPAIR 
Product Details
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$69.95
1981 to 1995 722.3 722.4 722.5 Modulation and Governor Pressure Test Kit
Now to both determine the internal health and to prolong the life of these old transmissions. Full video instructions included. 50 psi limit. This will NOT test full 190 psi supply pressure. Bonus speed adjustment video included
Too much pressure and you will blow the seals. Too little pressure and you will wear out the clutch packs. When installing a new vacuum modulator on your transmission, you most likely will need to adjust it. There are two ways to do this.
$59.00
1981 to 1995 722.3 722.4 722.5 New Transmission Pan Replacement w/ Magnets
Fits many models during that period. See complete list below. Late W123, Late R107, W126, W201, W124, R129 and W140
These transmission pans get "out of shape" due to over-torquing the bolts. That crushes the stops (see below), and when that happens, it is very hard to get the pan seal not to leak. Your best option if you are doing a transmission service is to replace the pan.