Hello there first time here. I have a custom build with a C4 transmission. Went for a test run for the third time and this time as I came to a stop it would not go into drive. No sounds or anything just simply would not go into drive has no problem going into reverse though. There’s not very many miles on this transmission at all since rebuild. I have a new vacuum modulator on order but any other pointers before I have to possibly do a dreadful transmission removal? Thanks so much in advance everyone