ok,this tranny has always grinded in third and fourth. i took it apart and found that the syncro's where worn bad and the syncro springs were mangled[litterally]. i was gonna buy a whole new set but the dog teeth was worn bad to and from my reseach you cant get the gears for the j1's anymore,different sizes from the 88-89 trannies. so i didnt want to put a new syncro set on a worn gear. so i just replaced the springs and put everything back together in hopeing that it would help the tranny some until i could just save up for a tranny in better shape. well 1,2,3,5,R gears work fine,but you have to baby it into 4th and it pops out when you give it gas,and you can feel the synro's grinding in the shifter if you try to hold it in.
now 4th gear was wore the worst,is this happening because of the new spring i put in,with the worn synro's and dog teeth or did i install something wrong,or could it be something else???? i also replaced the diff with a hydro diff for the hardend diff pin. im not new to trannies so please any of you experts could help me out

 

The engagement teeth are too worn on the sleeve and gear to hold it in place. Since the gear is no longer available, your only hope is to replace the sleeve and synchros.

 

i was hopeing you would chime in,you was the one i was refering to,i spoke to you on the phone a while back and told me about the gears being discontinued. what i dont understand is before i took it apart it stayed in gear,just grinded when it went in and now it wont stay in? is there any reason why? i mean they was worn really bad but it would stay in gear!!

 

Sometimes when you disassemble and clean the parts you remove the last piece of dirt that was holding it together

 

This. And try and find another used gear set that has a better dogteeth on the 4th gear set than yours. Need every bit that will help. :p

 

lol!!!! i see. well thats good in a way,cause i was worried that i put it together wrong,but i was 100% sure that i did it right. i may try a different shift linkage just to rule that out even though im sure it wont make a difference. it also has a short shifter where it didnt before. im just gonna rule everything out before i change trannies.

 

I had the same problem with my y1 transmission. I was gonna fix it but I didn't feel it would be worth the money to do so with how worn the dogteeth were and how expensive the gear would cost. Mine got to the point where 3rd was starting to fail but it was also only a 50 dollar b16 tranny I bought with a blown isb and bad syncro springs along with an ls tranny i took parts to fix it with.