well my 86 rx7 tranny linkage broke, so did the driveshaft at one time. Well i fixed that buy by taking my tranny to a school and having them swap the housings. I put the tranny in and driveshaft and the car runs.

Here is the problem i didnt know you was supposed to put a rear tail transmission seal before you put in the tranny, well now my car leaks gear oil from the ending of the tranny and the begining of the driveshaft.

And i have one more problem, i cant put my car into reverse, well i knew it worked before i had them swap the housings. Im thinking they fucked up and put it in wrong, but im wondering if my tranny oil is low would that cause me not to be able to put it in reverse?