Maxima Forums - Looking for Transmission Fluid articles - PepBoys replaced fuild, now I'm worried

You won't find anything written in stone. Nissan dealers are using GL-5 now too.

The two main issues are 1) the GL-5 may chemically attack the synchros, and 2) the extra low friction of the GL-5 will reduce the effectiveness of the synchros, which can lead to faster synchro wear and/or clunkier shifting.

1) is getting less likely by the day, as GL-4 becomes harder to find the oil mfrs are mostly making GL-5s that are compatible with GL-4 designed trannys. So those oils have GL-4 and GL-5 listed on the bottle. GL-5 is *not* simply a higher quality oil than GL-4 - it has higher additive amounts designed to bond more aggressively to the base metals. This is not always a more desireable behavior, and in our trannys it is detrimental. These EP (extreme pressure) additives are made of a variety of compounds, some of which (phosphorus and sulphur compounds) are bad for trannys designed for GL-4. It depends on the specific oil - some GL-5s include phosphorus and sulphur compounds in their EP additive package, and other do not use these compounds so that is remains it chemically friendly to GL-4 designs. Generally, the 'bad' GL-5 oils are cheaper and/or older formulations. I would press hard to see that Pep Boys discloses exactly what kind of oil they put in, and that it's at least listed as being both GL-4 and GL-5 certified. If it's only GL-5 certified, it could be of the kind that chemically attacks the brass.

2) This one you'll have to see for yourself, and Pep Boys probably can't be held responsible for these results. After all, Nissan dumps in the same stuff.

I reality, I think both of these are small differences in practice. But they are not negligible.

Dave