straight 40 weight vs a 15w40.

[Sushibar]

I know this might be the wrong forum but I couldn't find one that suits my query.

I have a marine transmission that specs a straight 40 weight but we a had a oil leak and all the 40w leaked out and all we had left was a multigrade 15w40 delo 400.

What is the actually difference between them and would this cause damage to my transmission as it seems to be slipping now at 3/4 load and higher and lots of foam in the oil when checked.

At idle the trans doesn't slip and doesn't foam.

Would the foaming be from the transmission or the multigrade oil.


The transmission is a ZF IRM 310
Oil spec is straight 30w.


Any thoughts would be greatly appreciated.


Jon

 

[Shannow]

So does it spec straight 30, or 40 ?

 

[Jim Allen]

It sounds like the problems have come because the unit was run low on oil or has another failure issue. I can't think of why 15W40 vs straight 40 would cause any short-term problems unless the oil specified is really something special (which I doubt) and the motor oil additive pack is totally incompatible. Your owners manual or your nearest ZF representative could tell you that. I submit that it's likely a moot point now that it's slipping. You'll get it repaired and they will install the correct lubricant (and take home an emergency supply!). FWIW, if you were out on the water and the trans was about to quit, you did right by adding the most compatible product you could find to get you to shore.

BTW, I live near Cloverdale.... OHIO!

 

[Volvohead]

Transmissions in marine duty can present higher shearing loads. For conventional lubes, a straight weight generally is a little more capable in that situation.

Just as with some DDs that demand a straight 40, some equipment won't run right unless you use the recommended weight.

I'd stick with a straight weight as recommended. But check with the manufacturer to be sure.

Foaming is usually in indicator of overfilling, but there may be other factors at play here.

 

[Chris71]

My local Napa carries Napa brand 40 wt. Maybe yours does too. Advance should have Shell 40 wt also. Hope that helps.