First gear jamming

Oldie · Oct 23, 2017

It's been a while since I asked a dumb question so thought I'd ask another one. I did ask about this some time back but I can't find the original post.
Anyway here's the story. It was getting hard to get into first gear and someone recommended trying some Nulon transmission treatment and it worked fine.
So a month ago, I changed the gearbox oil and stuck a tube of Nulon in also and it's fine while cold.
but after driving for bout half an hour, it's starting to jam again trying to get into first.
So I'm wondering, I used Castrol VMX 75W-85. is it possible the oil is thinning out too much when it gets hot and should I use a thicker grade oil or am I looking at another problem inside the gearbox.

Cheers

tweak'e · Oct 23, 2017

i would leave out the additives.
not sure if your problem was due to poor/old oil or not.
you may want to use a 75w-90 which will be a bit thicker and more suitable for warmer temps.

when is it hard to get into first gear? when your at idle or when down shifting?

Czechmate · Oct 24, 2017

I have a 98 mazda bravo with a very notchy heavy duty mazda 5 speed manual gearbox in it
It has always shifted much more easily and smoothly on castrol multitrax than anything else

jonney · Oct 24, 2017

sometimes if the clutch is abit worn or the clutch pedal doesn,t depress the clutch / pressure plate , 1 st gear can be hard to get into unless you double pump the clutch pedal before selecting 1 st gear. try this double pump and see if it makes any difference to selecting 1 st gear.

jack2840 · Oct 25, 2017

Syncoros proboly a little worn, dont think i would worry

Oldie · Oct 25, 2017

Thanks for the replies everyone.
If I'm slightly rolling and I mean slightly rolling, it will go into first.
If I push in the clutch and come to a full stop, that's when it jams and I have to try putting into neutral or another gear a couple of times to get it into first.
It's got me beat. Last few days it's been fine but this morning it did it again.
I'm stumped as the gear box is ok accept for this annoying BS that happens now and again.
Cheers

PS. the clutch is less than 2 years old and seems fine but I was wondering about as if it wasn't fully disengaging.