I just got my new motor and trans installed and the new 5th gear quit shifting the 2nd day of driving. It is a fresh '99 CTR swap, that I installed a new after market final drive and brand new LS 5th gear set in, Before I put the swap in the car. I put in about 2.5 Qts of 10w-30, and made a slow, 60MPH, easy drive to Arizona, (400mi) to check everything out; no racing or fast shifting. When I left there, to drive home, I was shifting normally into 5th gear and it ground real bad, like the clutch wasn't disengaged all the way. I tried it again to be sure, and same thing. The rest of the way home I couldn get it into 5th without grinding, unless I matched the RPM. All the other gears shift fine. It feels like the 5th gear synchro is plain broken, but everything in the tranny was like new when I put it together, including all synchros and sliders, and I was really babying it, because I didn't want anything to go wrong on the trip. It shifted fine for the first part of the trip, then all of a sudden just stopped shifting into 5th, for some reason.
I am gonna hate dropping out the sub frame again, to take it apart. It is a two week job in this car (a Morris Mini).
Does anyone know what could be causing this? Maybe not enough oil in the trans?

 

2.5 Qts of MTF is full in this trans. 5th gear can be damaged from low oil but I don't think this is your problem. It sounds like a broken 5th synchro spring. You will need to drop the trans for inspection to be sure.

 

If mainshaft wasn't properly cleaned debris could have blocked the oil port and caused 5th to run dry.

 

I guess there was about half of a gallon container of oil left, which is all i had handy at the time; so I guess that would be 2 quarts. Didn't think it was critical, as long as there was some in there. Tranny was spotless inside, and the countershaft was brand new, but maybe not drilled for oil holes,(aftermarket Final Drive). If 5th doesn't get enough oil, what happens exactly? bearings sieze up? or fall out? I need to drive it to the Anual western states and Canada Mini event in a week,(about 1,600 miles round trip), which I have been getting the car ready for, for over 4 months. Will it hurt the tranny if I keep driving it awhile? Haven't got much choice now; I'm going if I have to trailer it there. Thanks for your advice.

 

Drop the trans, inspect the 5th synchronizer, sounds like that little round spring is either chewed up, or its not there. Did you inspect the blocking ring to gear clearance before you installed it? If it's bottomed out, it will not function at all. Best to remedy that quickly before you seriously ruin the gear dogs and collar.

 

PM'd you...give me a call at the shop 909-476-7252