little grind hitting 4th

[jvandyke]

Thanks to all for helping me through my clutch issues last week. No longer have grind going into 1st or reverse. Only issue remaining is a little glitch/grind going into 4th. Not sure I can do anything about it, could be inherent in this used gearbox but thought I'd ask anyway, if there's something to be done that can save the gear I'll do it, otherwise I'll run it until it's fried while I rebuild the box I took out.
I tried hesitating a second as I go from 3rd to 4th, even tried double clutching (which I've never done before so I stink at it) but no matter what I get a definite little "grind" as I hit 4th. Maybe that synchro is going out? Looked fine on the bench but that doesn't mean much.

 

[texas_bugeye]

Change oil, apply clutch match RPM as best as possible pull and pray.

 

[Sarastro]

Fourth gear synchros going out is fairly uncommon--usually second goes first. (Hope that makes sense.) But I suppose it's not impossible.

Double-clutching is used to speed up the driving gear when you're downshifting--not necessary when upshifting. All you need to do on an upshift is pause for a second. If it still grinds, might be the clutch. but if every other gear works, and no grinding, say, when you shift to first at a stop, probably it's disengaging completely.

 

[jvandyke]

I've been dealing with grinding since the gearbox swap/clutch system rebuild. Until I put a nut under the slave pushrod I could not avoid grinding when going for first or reverse (it did this before the gearbox swap too but not quite as bad as I recall). I tried a different nut to push the rod out even further but it did not effect the 4th gear issue. Maybe I should go even further? Until I get clutch slip then back off? I don't know. I suppose it couldn't hurt to try even more, could save a gear. Really should get and try a 1275 slave push rod, that's longer by a bit for starters.

 

[jlaird]

The 1275 will only be as long as the 948 rod with a nut.

Could always have some welded on your present push rod to make it longer then it could be ground a bit if necessary.

 

[GeeBee1]

I think that the problem resides with the slave and not the trannie :wink:

Shifting into fourth at 1.5 to 2.0k should help, there is a rpm in that range where you can slip it with experience and not need the clutch, do not try this at home hehehe