A very common question/problem regarding the iron Turbo 350 valvebodies is the complaint of no reverse or weak third gear. This is caused by improper transmission rebuild during installation of the new valvebody.
This solution only applies to Hipster's Cast Iron Turbo 350 Transbrake (P/N: 32748 or 350BRAKE), ATD Cast Iron Turbo 350 Forward Pattern Valvebody (P/N: 32248), and ATD Cast Iron Turbo 350 Reverse Pattern Valvebody (P/N: 32148).
Your Hipster 350 Transbrake or ATD 350 Forward/Reverse Manual Valvebodies all require very specific direct drum prep to be followed, which is outlined in the instructions for each product.
The instructions state: "Assemble direct drum with two new lip seals on piston. Discard inner drum seal."
Failure to follow these directions will result in a no reverse and weak/no third gear condition.
For full versions of the instructions for these products, please see the links below.