overfilling a ZF: probably not so good

[RLDSL]

I was doing some *light* reading through some of my old spicer manuals and noticed that there was a big warning against overfilling. Aparantly a lot of guys were overfilling those things for teh same reason, to shut them up ( they do have some wicked rollover noise ), but the fill plugs are positioned on gearboxes for a reason so the lube can be picked up by the lower cluster and slung to the upper cluster. When you overfill ,the gears of teh upper cluster dip down into the lube and churn it up causing excessive foaming which leads to dry spots, which of course leads to premature wear and breakage." Overfilling usually results inoil breakdown due to excessive heat and aeration from the churning action of the gears . Early breakdown of the oil will result in heavy varnish and sludge deposits that plug up the oil ports and build up on the splines and bearings. Overflow of oil usually escapes onto clutch or parking brakes ( f450 /superduty tailshaft type parking brakes ) causing additional trouble."
I did some digging and found references in a few other manufacturers so it would obviously apply to the ZF as well since it universally applies to all gearboxes. So it looks like the use of a little extra lube to dampen case resonance may not be the best for the box in the long run.
I guess insomnia is good for something after all

 

[johnnyb1]

I've always put Lucas in my boxes. Helps the boxes but does nothing for my insomnia.!

 

[flareside_thun]

I'm not a fan of Lucas products myself but which one are you putting in the box?

 

[johnnyb1]

I just use "oil stabilizer". Alot of guys don't like Lucas. I've always had good luck with it. Same as their fuel treatment. I like Howell's also. Alot of guys don't like that either.

 

[Agnem]

This is why I overfill with 2 gallons of NON-DETERGENT streight 30wt. Motor oil. It doesn't foam, and I gaurantee you there is nothing dry in there!

 

[flareside_thun]

I was wondering about that Mel....2gallons of straight 30w?

 

[Dieselcrawler]

NON DETERGENT. non detergent is what older kohlers and air compressors use. it does not foam when aireated. i know that is spelled wrong. lol

 

[RLDSL]

Actually , at the time these old manuals were written, 30 and 50 wt non detergent motor oil were the standard spec lubricant for all of spicers boxes, so that is what this was written about.

 

[nsjames]

NON DETERGENT. non detergent is what older kohlers and air compressors use. it does not foam when aireated. i know that is spelled wrong. lol

You can find non-detergent motor oils at a small engine shop.

Actually , at the time these old manuals were written, 30 and 50 wt non detergent motor oil were the standard spec lubricant for all of spicers boxes, so that is what this was written about.

True, the Spicer box in my 1600 is spec'd for 30-50W motor oil depending on climate.

 

[Diesel_brad]

I wonder if my 6.8 qts of RELINE MTL is too much

 

[MIDNIGHT RIDER]

I think the over-filling practice has a lot to do with just what particular gear-box is in question.


It is a widely proven fact that the G360 GETRAG 5-speed, most commonly known as OEM in 1989-1993 Dodge/Cummins lives MUCH longer and behaves much better when over-filled by at least 1-1/2-QTs.

Standard plug-level factory-fill on those is 3.5-QTs; just about anyone in the know has been running 5-QTs instead.

The Getrag got an un-deserved bad name before it was discovered that the cure for it's ailments was simply adding an extra 1-1/2-QTs of lube.

Those running the extra lube have proven to be nearly bullet-proof.


I have also known of various gear-box (and engine) maladies being cured by pulling lube from the drain and pumping it via an electric pump such that it re-enters the box being sprayed into a problem bearing or gear.

Usually when this fix is performed, the lube is also routed through a stand-alone filter and auxilliary cooler as fringe benefits of the re-circulating pump, thus adding more lube capacity that also makes for more cooling.

 

[itsacrazyasian]

I wonder if my 6.8 qts of RELINE MTL is too much

Redline MTL does not foam. Mine is overfilled too, keeps my zf nice and quiet. Shifts real nice too with it in it.

 

[RLDSL]

I think the over-filling practice has a lot to do with just what particular gear-box is in question.


It is a widely proven fact that the G360 GETRAG 5-speed, most commonly known as OEM in 1989-1993 Dodge/Cummins lives MUCH longer and behaves much better when over-filled by at least 1-1/2-QTs.

Standard plug-level factory-fill on those is 3.5-QTs; just about anyone in the know has been running 5-QTs instead.

The Getrag got an un-deserved bad name before it was discovered that the cure for it's ailments was simply adding an extra 1-1/2-QTs of lube.

Those running the extra lube have proven to be nearly bullet-proof.


I have also known of various gear-box (and engine) maladies being cured by pulling lube from the drain and pumping it via an electric pump such that it re-enters the box being sprayed into a problem bearing or gear.

Usually when this fix is performed, the lube is also routed through a stand-alone filter and auxilliary cooler as fringe benefits of the re-circulating pump, thus adding more lube capacity that also makes for more cooling.

You may have a rare exception there where teh plug was possibly bored too far down in the case to begin with. You notice that's a pretty exacting amount that the overfilling seems to take care of the problem with that one.