What Additive Causes Clutch Slipping?

[tc1446]

In looking at UAO's of Rotella T6 vs Amsoil 10-40, for example, the main diff in additives are T6 is much higher in magnesium and lower in calcium. Other than that, I don't see
much difference. Both have about the same moly. What is the main purpose of magnesium and calcium?

Does anyone know what additive, other than moly, supposedly causes clutches to slip?

 

[Chris142]

I have ran all kinds of oils including moly addatives during break in and never had a clutch slip.

 

[GreeCguy]

Assuming you have a wet clutch, I had a somewhat bad experience with STP in my Case "D" tractor. Tried it in an effort to reduce oil burning only to discover the clutch slipped under heavy load. Granted under normal operation I experienced no problems but a few times while pulling a disc/plow in wet heavy soil the ole gal started slipping pretty bad. At first I thought the clutch needed adjusting but I changed the oil, (it needed changing anyway) just to make sure and the slipping stopped.

On the flip side of the coin, when I changed the oil, I added 3 cans of "Restore" plus one 32 oz bottle of "Motor Honey." Oil consumption reduced tremendously and no slipping clutch.

 

[tc1446]

Theres a lot of talk about wrong oil causing clutch slipping, and motorcycle specific oils are usually rated MA/MA2 and are advertised as not causing slipping. Some bike manuals point out that nothing higher than "SL" should be use or slipping might result.

I'm just curious about what ingredients other than moly, can cause slipping as I don't recall seeing that discussed before.

 

[AVB]

I think the biggest concern is whatever is used as the friction modifier in energy conserving oils.

 

[Clevy]

Its primarily moly that is warned against however I'm sure the "resource conserving" stamp means there is more than just moly being used as a friction modifier.
Anti-wear agents such as zddp don't contribute to a slipping clutch,its friction modifiers that need to be reduced.
I've got a friend with a Harley cop bike. Every year and a half he is needing some kind of clutch work done. I was lost as to why until I saw him using transmission fluid in his primary. Lots of slick stuff in automatic tranny fluid and iirc he was using ATF +4,the Chrysler spec stuff.
Alot of guys use oils with some moly in them but no clutch problems so I really can't say for certain that its guaranteed to cause slip. I think it depends on clutch material,type of clutch,heat,pressure etc.
Moly plates parts that touch each other with pressure forcing the plating mechanism. Maybe how a riders riding style is a contributing factor as well. If a person slips it less the moly cannot achieve the variables required for plating to commence,whereas if a rider rides the clutch and heats it up more this contributes to a more favourable condition for the plating action.

Just spitballing.

 

[Mackelroy]

One thing to note, oil induced clutch slippage is very suttle with a sound clutch.

Several years ago I ran some redline car oil in one of my bikes, I was actually on the second oil change with this oil or about 3,000 miles with running that oil. On sustain highway speed, I'd feel some clutch slippage for a scond and then not, It was so suttle I thought it was in my head. So I took the bike out for a big test, I had a 1 mile straight up mountain, and just burned through the gears, and when I hit top gear (the most load on the clutch, it was obvious There was slippages, as the clutch was obviou)sly intermittantly breakin loose and reengaging. Went home and switched back to a known good clutch oil and no more issue, redoing the test.

Recently in the last year or so, redline has new mc Ma rated motorcycle oils(they used to be MB rated). But they've taken alot of the moly out of the mixture, in comparison to the car stuff. Ive got 3 quarts Im about to try out in another bike.

 

[BusyLittleShop]

Technically speaking a wet clutch in good working order is not about
to slip no matter what oil the owner selects... what is confusing the
issue is the fact that all motorcycle wet clutches will reach a point
in their life and start to slip... have you notice that no one
complains about clutch slip when new... its about the 27K to 57K range
that contaminants build up to point where the clutch may begin to
loose its grip most noted during a WFO (Wide Fooking Open)throttle
burst... in error the oil could be blamed but technically speaking its
really the condition of the clutch plates...

I've been using 10/30 Energy Conserving Mobil 1 since 98 in
Mr.RC45 with no clutch slipping due to oil being certified
10% slipperier than non EC oil... and it's a bike with a tall
first gear good for 90mph that's known to incinerate clutch
plates...

Quote SportRider
Can synthetic oils cause my clutch to slip?

"To answer this in one word: No. Clutch slippage is caused by
many things, but the use of synthetic oil alone is usually
not the culprit. The truth is that some bikes seem to suffer
clutch slippage no matter what oil goes in them, while others
run fine with any oil. This is most likely caused by factors
other than the oil, such as the spring pressure, age and
clutch plate materials".


Quote Mark Junge, Vesrah's Racing representative

"He said that in his years of engine work he has yet to see a
slipping clutch that could be pinned on synthetic motor oil.
Junge felt that nearly every time the clutch was marginal or
had worn springs, the new oil just revealed a problem that
already existed."

Friction modifiers additives are only a small percent of the total oil
product and help the base oil do things that it otherwise could not...
Additives fall into several basic categories but Moly is the most
often used friction modifier because it has such a high melting
temperature (4730¯ F versus 2795¯ F for iron), it works great as a
high-temperature, high-pressure antiwear agent. Some claim that
because moly is so slick, it can cause clutch slippage... but note
that 6 of the 19 motorcycle oils Sport Rider tested used moly
including the HP4 market by Honda for any of their motorcycles...

 

[AVB]

Originally Posted By: Clevy
Its primarily moly that is warned against however I'm sure the "resource conserving" stamp means there is more than just moly being used as a friction modifier.
Anti-wear agents such as zddp don't contribute to a slipping clutch,its friction modifiers that need to be reduced.
I've got a friend with a Harley cop bike. Every year and a half he is needing some kind of clutch work done. I was lost as to why until I saw him using transmission fluid in his primary. Lots of slick stuff in automatic tranny fluid and iirc he was using ATF +4,the Chrysler spec stuff.
Alot of guys use oils with some moly in them but no clutch problems so I really can't say for certain that its guaranteed to cause slip. I think it depends on clutch material,type of clutch,heat,pressure etc.
Moly plates parts that touch each other with pressure forcing the plating mechanism. Maybe how a riders riding style is a contributing factor as well. If a person slips it less the moly cannot achieve the variables required for plating to commence,whereas if a rider rides the clutch and heats it up more this contributes to a more favourable condition for the plating action.

Just spitballing.


ATF is used in a lot of 2 stroke MX bikes. I don't know of any manufacturers that recommend it, and it is only recommended for a very short oci though. A motorcycle wet clutch is very similar to the clutch packs in an automatic transmission. Most atfs are friction modified the same way as a limited slip additive or Lubegard to combat tcc shudder. It is a different type of friction modifier than motor oils use.

 

[Ken2]

TC, it isn't widely know what in oil makes a clutch slip. It certainly isn't a synthetic base oil. There are several different forms of molybdenum compounds that are used in motor oils, and some forms might be problems while other forms are no problem.

A virgin oil analysis of Shell Rotella T6 5W-40 shows 42 ppm of some sort of moly. And Shell says that this oil would pass the JASO-MA wet clutch test. Schaeffer's 707 20W-50 motorcycle oil contains two friction modifiers, both their moly compound plus their proprietary Penetro friction modifier, AND passes Jaso-MA2.

By the way, JASO-MA was cut into two parts--the lower friction half is MA1 and the higher friction half is MA2.

 

[rossn2]

Quote:
A motorcycle wet clutch is very similar to the clutch packs in an automatic transmission


Can someone please show me the Torque Convertor on a motorcycle that converts mechanical energy into Hydraulic Fluid pressure?

I've used Schaffers Supreme 7000 20w-50 (high in moly), Amsoil MC 20w-50, Valvoline MC oil, Redline MTL (yeah the stuff that goes into manual transmissions), SYN3 and NEVER had clutch slippage in any of my four Harleys!

 

[AVB]

Originally Posted By: rossn2
Quote:
A motorcycle wet clutch is very similar to the clutch packs in an automatic transmission


Can someone please show me the Torque Convertor on a motorcycle that converts mechanical energy into Hydraulic Fluid pressure?

I've used Schaffers Supreme 7000 20w-50 (high in moly), Amsoil MC 20w-50, Valvoline MC oil, Redline MTL (yeah the stuff that goes into manual transmissions), SYN3 and NEVER had clutch slippage in any of my four Harleys!


That is the job of the pump not the torque converter. The torque converter has nothing to do with the similarity between the clutches.

 

[BusyLittleShop]

True but deceptive... Motorcycle wet clutches are similar in shape to Auto but differ in grip
material... Auto plates employ Sintered metal like on our brake pads whereas Motorcycle
clutches employ Kevlar or Cork...

 

[AVB]

Originally Posted By: BusyLittleShop

Not all of them, I have never seen a sintered metal plate in an automatic, not saying they don't exist though. Here is a pic I just took of a couple plates out of a 4L60E kit that I have. It is some kind of paper/fiber friction material.

 

[AVB]

Here is a close up.



I wouldn't use atf in the transmission of a Harley, but it does work with short intervals in 200# MX bikes.

 

[onegudman]

Originally Posted By: tc1446
What is the main purpose of magnesium and calcium?


A lot of replies but I didn't see that anyone answered this questions. My understanding is that the magnesium and calcium act as buffering agents to neutralize any acids that form in the oil over time. This contributes to a high TBN (Total Base Neutrals) number. As motorcycles often spend longer times sitting around without being run compared to cars/trucks, the ability for the motorcycle oil to neutralize acids is important. In general, the higher this number, the longer the potential oil change interval.

 

[Ken2]

Magnesium and calcium compounds (never magnesium or calcium elemental metals), often magnesium sulfonate or calcium sulfonate, are part of the detergent compounds in the lube oil. These detergents do offer some acid neutralization.
http://www.pqiamerica.com/magnesium.htm
https://www.oronite.com/products/detergents.asp

When picking oils, look at the actual results in service, not a data sheet. The starting TBN of an oil is not as important as the finishing TBN when the oil has become exhausted and is due for change. Often the oil is due for change due to loss of viscosity, oxidation limits, depletion of ZDDP, etc., and it may still have an adequate TBN.

 

[tc1446]

Thanks to all of you for some fine feedback. I surely am more informed than before and will feel more confident in my oil selection. I normally use Amsoil but as of yesterday did my 4000 mile change and am trying for the first time Castrol 10-40 blend to see how it does. Will send a lab test in at 3K as I've done with other oils for comparison.

It'll be some time before I get 3K on it but will report it here when I do. I recall some folks said friends don't let friends use Castrol so I just have to give it a shot to see for myself. LOL.

 

[sunruh]

Originally Posted By: tc1446
I recall some folks said friends don't let friends use Castrol so I just have to give it a shot to see for myself. LOL.


consider this a de-friend then!

 

[tc1446]

Originally Posted By: sunruh
Originally Posted By: tc1446
I recall some folks said friends don't let friends use Castrol so I just have to give it a shot to see for myself. LOL.


consider this a de-friend then!

Now you've hurt my feelings! LOL

Will be sure to let you know how my lab test comes out...good or bad. My Can Am seems to be particularly notional about oil and shears like crazy. Figured since the BRP Company touts their brand of Semi-syn (not otherwise identified but assumed to be Castrol) and says it good for 4600 mi I'd give Castrol a try. If it turns out better than Amsoil, I can get it cheaper, whereas BRP oil is outrageously expensive. I'm sort of a notional person too.