1st gear grinding (NG3)

[BDA]

Recently, it started to become difficult getting into 1st gear on my NG3 tranny. It started pretty suddenly on the way back from an hour drive a few days ago. It happened again the next day. It seems to be harder after the car has warmed up a bit. The best way to get it into gear with minimal (usually none) grinding is to firs try to shift into 2nd. Usually that will be unsuccessful and I "row" between 1sh and 2nd till it gets into one of them - usually 2nd. Then I can get into 1st. I have no problem getting into any other gears. The tranny oil is topped up. Cursory inspection of the shift linkage showed nothing amiss.

Never having dealt with this before, I am thinking that my problem is probably with 1st (and maybe 2nd) gear synchros. Can somebody check me on this? Is there an alternate explanation?

Since I don't know how many miles were on this box before I installed it (I have probably put around 20,000 miles on it), it may be time to go through it. Has anybody been inside an NG3? Any tops, tricks, watch out fors, be sure tos?

[Pfreen]

I don't know about an NG3 but with my 365, which I assume is similar, it was always difficut to engage 1st gear.  Even after I rebuilt it with new synchros.
Perhaps you could play around with gear lube.  The friction coefficient, which the oil affects, could change the synchro behavior.
I don't shift much into 1st moving.  If going fast, I double clutch to prevent grinding.  I have just learned to live with it.  I think all the other gears shifting up or down is excellent.  Although 5th is a pain to get into.

[kram350kram]

Clutch disengaging all the way? Does it go into reverse without grinding?

[BDA]

Thanks Pfreen. I generally use 1st only to start from a stop, so my problem happens mostly at stop lights. I’ve been using Red Line 75W90NS for years without problems. 1st has never really been a problem before and I am careful when getting into 1st (I’m not really sure why!).

Getting into 5th with my NG3 has never been as difficult as getting into 5th in a 365 but the odd thing is that it seems like it could be even easier lately. I’m wondering if this could be related…

Thanks kram, yes clutch completely disengages and I have no problems getting into reverse but I will double check my clutch adjustment!

[kram350kram]

Reason I was asking about clutch disengagement is a grinding gear means the disc is still turning gears, so not disengaging completely from the spinning flywheel/pressure plate, but you probably know that.

[SwiftDB4]

How big diameter are your tires and is your diff 3.77? With my NG3 1st is so low I never use it. Just start in second and no problems. I can get the trans into first, but fairly stiff.

[BDA]

Thanks Swift, my rear tires are 205/50-15 which is a similar diameter to the stock 185/70-13. I don’t know my rear end ratio or my 1st gear off hand but I don’t think it’s low enough not to use it. In any event I haven’t considered it. Either way, this is something that came up rather abruptly. 1st gear has never been a problem before and it seems to be more prevalent after I’ve driven a bit.

[jbcollier]

On Renault transaxles, a slow shift, especially when cold, will result in 1/2 gear “grinding” as the gear reaccellerates after the synchro does its job.  The oil is too cold to allow things to work properly.  Your box has changed behaviour so it is a matter of tracking down what has changed.  My suggestion would be to start with an oil change and a careful examination of the linkage, front to back.  You’re looking for something that would slow the shifting down: a dry bushing/joint perhaps.

[BDA]

Thanks JB. I’ll be checking that out.

[Clifton]

Clutch not dis en gauging fully could do it. What seems like enough at 3000 rpm is not at 7000 rpm.

Or fluid.

I oopsed and put GL5 in my Nissan truck after a disassembly. After a few thousand miles of syncro unfriendly fluid, I got the grinds. Miata guys have poor syncros and use a Castrol made Ford fluid, XT-M5-QS I used it and it shifts great now at 355k miles. I used in my MR2 trans too. A lot of MR2 guys swear by Redline shockproof. Just don't put a GL5 not designed for syncro's. It's too slick and you will have problems.

[BDA]

Thanks, Clifton.
Interesting. According to Red Line, the NS specified gear oil is made to be used with synchros. They claim it slows the synchros down for smoother shifts and also has improved corrosion protection for the copper in the synchros for longer life. I did email Red Line and they said with the Renault ring/pinion orientation that a GL-5 oil is not necessary and that their GL-4 oils such as MT-85 would also be appropriate. Looking at Red Line's description of their Shockproof gear oils, it seems they are mainly for dog ring gear boxes and specifically not for synchro gearboxes. In fact, they don't give them a GL spec. I agree they would be a bad choice for most of us.