I recently decided to rebuild my trans (M5R1) as it was getting notchy going into every gear. Dropped it and tore it down. Replaced all 6 synchros and all seals while i was at it. Other than that everything was perfect, NO damage at all. After getting it all together again, it would jump out of first and was hard to get into second. So i dropped it again and the consensus was that the 1st/2nd synchro assembly was backwards. Tore it down and flipped it around, this time with guidance from the interwebs (several well documented rebuilds). Got it all in the truck again today, and once again it jumps out of 1st. Goes into every other gear just fine, no other issues, just whenever i give it power in 1st, it bangs and pops into neutral.

Does this trans have any linkage adjustment that i missed? What might be causing this to happen?

Thanks in advance!

 

Detent ***** and springs on the shift rail could be worn for 1st.