Cameron Morison
5+ Year Contributor
- 51
- 46
- Nov 12, 2018
-
Christchurch,
New_Zealand
I've just ordered some parts to do a freshen up on my PAR gearbox, I've noticed 2nd gear has got crunchy even when shifting slowly. This gearbox I built a couple years ago with good condition used synchros, they had nice sharp teeth that had good clearance and grabbed my thumb pad really well. 1st gear is obviously still single cone, 2nd, 3rd and 4th gear are evo 3 double cone. 1st, 3rd 4th and 5th are still mint. It does seem a little bit odd as its not been raced in a while but last few leisurely drives around the block I had zero issues with the synchro but driving it yesterday it was really bad but only 2nd gear.
There is a chance that a synchro key spring has come dislodged. I did the double-up trick on them with 4 springs in there. The other possibility is that the synchro is simply worn out. The car is a hillclimb car so gets driven hard, clutch is a tilton twin and confirmed no clutch drag. I was wondering what other people experience with synchro life?
Oil wise I have to use Penrite Pro-gear GL5 75w90 for the gear set, there is a motul option but they are all 'synchro safe' GL5. One thing Ive noticed about the 2nd gear synchro is it has incredibly fine teeth inside it, unlike the evo 3 3rd and 4th, and all of the nissan gearboxes I've worked with previously. I can see this could potentially limit its ability to cut through a strong oil film and would make it less tolerant of wear.
There is a chance that a synchro key spring has come dislodged. I did the double-up trick on them with 4 springs in there. The other possibility is that the synchro is simply worn out. The car is a hillclimb car so gets driven hard, clutch is a tilton twin and confirmed no clutch drag. I was wondering what other people experience with synchro life?
Oil wise I have to use Penrite Pro-gear GL5 75w90 for the gear set, there is a motul option but they are all 'synchro safe' GL5. One thing Ive noticed about the 2nd gear synchro is it has incredibly fine teeth inside it, unlike the evo 3 3rd and 4th, and all of the nissan gearboxes I've worked with previously. I can see this could potentially limit its ability to cut through a strong oil film and would make it less tolerant of wear.
