My shifter runneth over -- oil in shifter assembly. Normal?

[LeonV]

All,

The reason the manuals say fill the TM to the level of the fill plug is because the level matters; the actual volume does not. The reason the level matters is because the engineers determined the fill level required to keep the gears immersed in oil, even while cornering at high g's*. Too low, and some parts get starved for oil (Older Honda's are known to lose 5th gear if the oil level is allowed to get too low.)

However, having the oil level set too high will cause the oil to get whipped up by the gears too much and foam, reducing it's ability to lubricate. It will also tend to beat up the oil faster and loose some of its carefully engineered properties. Finally, it will cause unnecessary drag thereby reducing fuel economy.

Mind you, this is not a precise science, but it is more precise than simply focusing on the volume.

The reference to the fill volume is so that you have some idea of how much you need to buy before draining it. Part-to-part variation will result in some transmission cases having a slightly larger or smaller interior volume. The important thing is that the fill level is correct because that is what the manufacturing process engineers control most tightly in order to get the expected lubrication.

Al

* In a quasi-static state, cornering at 1 G, for example, will put the surface of the oil at a 45 degree angle to the normal level (assuming the car doesn't lean). At that condition, the gears must still be partially immersed in oil in order to properly splash lubricate.</SPAN>

Thanks Al, it's good to have some people who actually understand this. I was typing as you posted.

[Zed Head]

This topic is really more about how to interpret the FSMs. Which is a pretty interesting topic anyway. I don't that that you can determine "reason" from the FSMs. Fun to guess though.

Food for thought - how is the fluid level determined and what should it be when climbing the Rockies? The same for descending. How long can you climb the Rockies before needing to turn around and back up the mountains to re-lube the dry parts or to let the foam subside? Do Zs in San Francisco suffer more lubrication related transmission problems than Zs in Illinois?

If it was super-important, there would be a sight-glass or dipstick installed to verify correct fluid level range. Like in an engine,where it is super-important, but there is still a one quart safe range. Also, Nissan surely would have put one of those cartoon guys in the FSM, sticking his finger in the fill hole to check level. No cartoon guy - not that important.

(p.s. I'm kidding)

Edited December 1, 2011 by Zed Head

[240Z-Fan]

Zed Head,

Climbing the Rockies would be the easy part, it isn't that steep, it is the hard braking and acceleration maneuvers that have to be factored. In automatics, the filter inlet has to remain covered or the trans will slip.

As for glass sight tubes, they are used extensively during the development process. Also, Plexiglas windows are installed in the cases so the engineer can (try to) see what is going on.

Then you have to realize that fluid expansion and contraction is a big part of it too as the volume changes a lot from -40 to +300. Then you need to consider fluid viscosity changes as it flows very slowly at very low temperatures. Some automatics have a fluid storage area with a thermostatically controlled valve to compensate for the fluid volume change.

With all that said. There are some conditions where not all the criteria can be met....

Al

Edited December 1, 2011 by 240Z-Fan

[sblake01]

There actually was a dip stick on the column shift 4 speed in the 320 pickups. There's a roughly 4" rubber plug in the floor that allowed access to the dipstick......

[LeonV]

This topic is really more about how to interpret the FSMs. Which is a pretty interesting topic anyway. I don't that that you can determine "reason" from the FSMs. Fun to guess though.

Food for thought - how is the fluid level determined and what should it be when climbing the Rockies? The same for descending. How long can you climb the Rockies before needing to turn around and back up the mountains to re-lube the dry parts or to let the foam subside? Do Zs in San Francisco suffer more lubrication related transmission problems than Zs in Illinois?

If it was super-important, there would be a sight-glass or dipstick installed to verify correct fluid level range. Like in an engine,where it is super-important, but there is still a one quart safe range. Also, Nissan surely would have put one of those cartoon guys in the FSM, sticking his finger in the fill hole to check level. No cartoon guy - not that important.

(p.s. I'm kidding)

I don't know about you but it's pretty easy for me to interpret, "fill to the plug hole." Not much lost in translation there.

FWIW, there is a cartoon finger sticking a finger in the fill hole (MA-25, '81 FSM), so I guess it is important!

Comment about "finger in fill hole" in 3...2...

[beermanpete]

This topic is really more about how to interpret the FSMs. Which is a pretty interesting topic anyway. I don't that that you can determine "reason" from the FSMs. Fun to guess though.

Food for thought - how is the fluid level determined and what should it be when climbing the Rockies? The same for descending. How long can you climb the Rockies before needing to turn around and back up the mountains to re-lube the dry parts or to let the foam subside? Do Zs in San Francisco suffer more lubrication related transmission problems than Zs in Illinois?

If it was super-important, there would be a sight-glass or dipstick installed to verify correct fluid level range. Like in an engine,where it is super-important, but there is still a one quart safe range. Also, Nissan surely would have put one of those cartoon guys in the FSM, sticking his finger in the fill hole to check level. No cartoon guy - not that important.

(p.s. I'm kidding)

Driving up and down hills, at various altitudes, extreme weather conditions, etc., are all part of what is considered during the design process. The oil level is set at a point that will accommodate anticipated conditions. This is why the fill plug is located where it is. A sight glass or dipstick would certainly be a useful feature but impractical to implement in the case of many car designs. You fill the gear box until the oil level is even with the bottom of the hole, or nearly so at least.

I have worked in automotive and motorcycle service shops and the general practice has always been to fill until the oil is even with the hole. Level checks during routine service involve poking a finger in there to feel for oil. If none is detected it gets oil until it runs out. Precise? No. Suitable? Yes.

[doradox]

Precise? No. Suitable? Yes.

I would argue that it is a precise way to fill the trans to the correct level. Diff and trans housings are castings with tolerances that aren't very tight. The internal volume of a cast housing can vary because of that. So the volume of oil to reach the fill plug level can be different between one trans and the next. Hence the approximate fluid capacity listed in the FSM. The fill plug location is pretty well controlled because it is machined into the casting along with the other features that position the gears in the housing. So, the oil level with respect to the gears is fairly precise if one fills to the fill plug.

Steve

[240260280z]

I think it is a moot point. So long as the gears are lubed is the main thing.... filling to the spec and not reaching the drain hole, or over filling the spec. and reaching the drain hole depth seems to have little difference from reports here and from inspection of the drawings.

As for oil at the base of the shifter.... was it poured in by past owner to lubricate or did it sling out? I think the first.

[sblake01]

I recall reading here a few years back about someone who thought you could fill if form there.....

[cygnusx1]

I have never had an F series datsun trans that wasn't oily at the base of the shifter. Oil slings everywhere in there. Don't worry bout it. Put the inner shifter boot on with a zip tie to contain it.

[FastWoman]

Ah, Blue, thanks! So people DO sometimes fill these things with oil!

Dave, the zip tie is a great idea. I'll do that.

Thanks, guys!

[doradox]

I think it is a moot point. So long as the gears are lubed is the main thing.... filling to the spec and not reaching the drain hole, or over filling the spec. and reaching the drain hole depth seems to have little difference from reports here and from inspection of the drawings.

As for oil at the base of the shifter.... was it poured in by past owner to lubricate or did it sling out? I think the first.

You are correct. Moot point. Use the approximate fill value from the FSM for a generic instance of your transmission or the precise amount of fill for your individual transmission by filling to the fill plug.