Triton318

I'm getting ready for a long trip, so I went to check my manual transmission (AX-15) oil/fluid. As I was backing the fill plug out, oil began to run out of the fill hole. I tightened it back up quickly.

I know that the correct amount of oil is just to the bottom of the fill hole. How could the level be higher than the bottom of the fill hole? If you're pumping oil into the fill hole, you'd have to stop when the oil begins to drip out and replace the plug.

Could it be that the level is correct, but for some reason, there was some oil trapped above that level in the gears? The vehicle is parked on level ground.

Thanks.

PatHenry

It's certainly possible to overfill the transmission and you definitely DON'T want too much fluid.

The AX15 takes gear oil per the spec, so it's oil.. oil is runny and when it's thrown around by moving gears, it coats everything. If it's leaking a little out when you remove the fill plug, it's normal. You can either let it drain out until it stops or probably leave it if it wasn't pouring out.

00t444e

That's no problem at all, I just dump a gallon in mine through the shifter hole. Some transmission shops recommend overfilling it some for better lubrication.

BlueRidgeMark

Well, that's very interesting! Two very different views of overfilling a transmission!


The difference is automatic (never overfill) and manual (can't really overfill). There's no real huge hairy problem having "too much" gear oil in a manual trans. It might blow out the vent, causing hysteria and angst as you wonder where the leak is coming from. Some say too much will make it hard to shift, but I'm skeptical of that.

PatHenry

My feeling on the matter is the general concern with too much oil - potential damage to seals etc. Considering that the typical AX15 is going to be over 20 years old, I wouldn't want to stress it unnecessarily.

Now sure, a manual transmission is probably more tolerant of over filling since it's not pumping it around, but again, the spec is the spec for a reason. I don't think we're in as much disagreement as we're talking a "bit" over vs. grossly over.
Also, the AX15 is a damn solid transmission - possibly one of the best ever made, so I'd be a heck of a lot less worried about it than others. I can say that I definitely would NOT trust the NV3550 and would be awful worried about even a "bit" over, but I'm biased against that piece of junk.

For the O.P.'s purposes, my point was that his experience is normal and he's good to go unless it was pouring out in which case, I would let it run down to the spec. Even the FSM mentions "just below the hole" as well as "fill until fluid seeps out" seemingly interchangeably.

Triton318

Thanks for the responses. I ended up draining it and refilling with new oil anyway. That was about the easiest thing I've done yet on my XJ. I'm glad I did it too -- the oil that was in there was almost black and smelled burned. BTW--I decided to go with synthetic 10W-30, as I don't have time to get any Redline MT-90 mailed to me (and it's not available locally). I may change it out after my trip.

Thanks again!

PatHenry

Nice!
I love the MT90 which I'm running in my 95. It is a bit pricier than other options, but it's synthetic, it's safe for the soft metals and is specifically designed for GL-3 gear oil lubricated manual transmissions such as the AX15. My transmission shifts smooth, quiet and seems to run a bit cooler with it as measured by my unscientific method of feeling the floor above the transmission.

You can also buy it by the gallon and dump it down the shift tower if you like. I filled it with a bottle pump from a 1 gal. container and had a little left over after it started running out the fill hole.

BlueRidgeMark

Not a bad plan. That 10-30 should give it a good bath, and then another drain and fill with the good stuff will put you in good shape.