Well, after an extensive rebuild of my original NVT-350 trans this winter including all bearings, synchro's, shimmed Quaife LSD, I'm now having a significant grind going into 2nd gear if shifting quickly. All other gears shift flawlessly fast or slow. If I very very slowly shift into 2nd it will go in no problem without grinding. I followed the rebuild videos by Little Dragon Racing, which I highly recommend purchasing if anyone is looking to rebuild! (email [email protected]). During the process everything assembled easily, and I verified all was in working order before installing in car.

For the build I re-used the gears, sliders, forks, etc. because they didn't look too worn, only new synchro's (all brass) and needle bearings installed onto both shafts. The grinding into 2nd gear wasn't something I experienced before the rebuild. For fluid I'm using valvoline synchromesh, I hear stepping up to Redline MTL or MT90 may help? It feels as though the 2nd gear synchro is working but is taking much longer to speed up/slow down the gear to allow the slider to engage. Is it possible I need to put more miles on the trans to allow the new synchro's to "seat" or break in?

Appreciate any info, I'll add some photos here this afternoon.

Pictures below

The brass synchronizers I have found to give more feedback per say, more "mechanical" feeling while shifting. However there should be no grinding if your clutch is properly functioning. Did you replace the two larger bearings at the end of the case?

BLACK'98DSM said:

The brass synchronizers I have found to give more feedback per say, more "mechanical" feeling while shifting. However there should be no grinding if your clutch is properly functioning. Did you replace the two larger bearings at the end of the case?

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I agree, although all other gears shift like "butta" as they say. 2nd gear is the only one giving me trouble. Clutch is disengaging properly. Yes I replaced both large bearings on the ends of the shafts. Is it possible the whole shaft is moving when I try to get into 2nd?

If an entire gear shaft or shift fork were either axial, or "sliding/shifting", and having enough play to cause issues with one gear... Then issues with other gears would be noticed as well. For example, I had an issue with popping out of fifth gear but it also happened with first gear and opposite. One of my larger case bearings were ruined along with the snap ring and bearing cover. That particular issue itself is rare, but. Reverse has it's own bushing and synchro. The gears are separated to a certain degree. If only one gear has an issue, you should be suspect of that specific synchro or gear on the stack. 1&2 share a synchro, I'd assume you also know. That's not to say the synchro is perfect or within specs as either side of the shaft could be worse than the other, and more issues than that. And although a shift fork bending/breaking is rare, it has definitely been recorded and should be checked.
Unfortunately, any way I see that this goes, I don't think it's possible to diagnose or resolve with the transmission still assembled. You will probably have to separate the belhousing from the case to know for sure.


I would check the shifter cables and bushings to still be in tact before removing and opening a transmission of course. But if that all checks out let's see what happened inside.

I've done some more research and came across this post describing a similar issue of the shafts moving axially within the case. Although this one has more to do with 5th gear popping out. I recall when assembling my case during the rebuild, there was some axial movement of the countershaft, even with new bearings pressed on and the snap ring installed. The only thing stopping this axial movement is the rear backplate/cover at this point.

Is it possible when I try to get into 2nd gear, which in fact moves the 1-2 fork towards the back of the case (towards rear bearings) that there is some axial movement of the counter shaft and that does not allow the synchro to engage? Thus grinding?

I'm planning on tearing off that rear cover to see if there's anything obvious. Maybe try tapping the rear bearings on more and install new snap rings, which I haven't been able to locate as they are discontinued.

Ref. post - https://www.dsmtuners.com/threads/transmission-pops-out-of-5th-gear-and-sometimes-4th.518296/

Post a picture of the bearings and snap rings once you have the cover removed. And make sure you have some RTV or anaerobic sealant ready. Normally an issue with those components is visible. Also drain the fluid through a strainer and see if anything chunks or shavings come out, and post a picture if so. I normally install a magnetic drain plug on these transmissions.

You would most likely have an issue with gear pop outs or shifting with multiple gears if the shafts have too much play. But I wouldn't rule it out without inspecting. The most common issue, while rare, is popping out of 5th gear if that shaft has excessive play. That normally means some part is worn past tolerances.

I'll upload photos for sure. Been thinking more about it today, and agree with you, even if there was end play this would be more of an issue of gears popping out, not so much grinding... I may have to bite the bullet here and pull the trans to see what's going on.

I completely dissembled the output shaft during the rebuild, possibly one or more of the 1/2 slider keys/ball bearings/springs are out of place? Do you know if the 1/2 hub goes on 1 way or not on the shaft? Slide collar?

Will update here as I progress!

I had a similar issue in my AWD trans. Turned out it was a goofy year that required a different synchro "key" Ramp style. Short vs long. Not sure if these have different ones or not but the keys put pressure on synchro and help with the slider to slide down onto the engagement teeth of the gear.

It sounds like the back side of #2 syncro is not slowing the gear down, for whatever reason. Did it seat on the cone nice and smooth. The back slows the gear down to engage it on the gear "dogs". Just a question is all. If you have any "slop" on a shaft, that should be addressed as mentioned. Good luck!