Re: gear grinding during shifts to second gear.

Posted by DrewLA On 2016/8/1 13:08:29

If you only experience gear clash when going into 2nd on an up- or down-shift, it's likely the 2nd gear synchronizer is worn, because if it were merely an issue with fluid, the shift to 3rd would likely experience some clash as well. However, if you've lived a pure life, you may find changing the fluid will ameliorate the problem.

Straight 90 GL-1 can be hard to find, but NAPA does carry it, albeit occasionally only by special order. Most gear lubed out there are GL-4/GL-5 for Differentials, and many times you'll notice the label will say "GL-4 for axles only, not for manual transmissions" or some similar language.

An acceptable substitute is SAE 40 engine oil -- in fact Borg-Warner specified that as their preferred lube in some of their overdrive transmissions (T85/86).

In newly rebuilt transmissions I've used a synthetic gear live intended for older manual transmissions to hopefully maximize the lifespan of the rebuild. Amsoil has a manual transmission oil that specifies its suitability for older transmissions that is GL-4 rated for transmissions (which means it won't harm the yellow metals in your trans).

If you're experiencing clash, be careful and slow down your shifts-- if the synchronizes aren't doing their job anymore you could end up plutting a knife-edge finish on the gear teeth necessitating gear replacement rather than a more conventional synchro and bearing rebuild.