Lubrication

[raybee]

Hello all. Any comments about using Rotella T 15W40 ?

Also - looking to change the tranny (manual) fluid - I have the Valvoline 80W90 Gear Oil. Chiltons mentions GL5...not sure what that is.

Thanks!

 

[Antz81]

Also - looking to change the tranny (manual) fluid - I have the Valvoline 80W90 Gear Oil. Chiltons mentions GL5...not sure what that is.

The container should say on it what it is.
valvoline 80w90 is available as GL4, GL5, and GL5 LS.

 

[Peer81]

Rotella T is the oil to use if you want to keep using your aftermarket non roller hydro cam.

Greetings Peter

 

[Hib Halverson]

If you're going to use petroleum based lubricants, in the engine I'd use Rotella T 10W30 rather than the 15W40. It's harder to find but Wal-Mart shows it on its web site.

For the transmission, ideally, if you're going to use a petroleum-based gear lube, you want an SAE80W90 or an SAE90 which meets GL4. Problem is most of what's on the market these days is "multipurpose"/GL5-rated. GL5 is actually a spec for lubricants used in rear axles. In short, for a four-speed manual, a GL5 will work, but a GL4 will make the trans shift nicer.

For best possible lubrication, if it were my car, I'd go to synthetics and, for an '81, I'd use Joe Gibbs Driven HR 10W30 in the engine and Gibbs Driven STF in your four-speed. The HR 10W30 engine oil has an appropriate level of of ZDDP additive to ensure durability of a flat tappet camshaft. The STF, is a synthetic equivalent of an SAE90 GL-4 gear lubricant.

 

[raybee]

If you're going to use petroleum based lubricants, in the engine I'd use Rotella T 10W30 rather than the 15W40. It's harder to find but Wal-Mart shows it on its web site.

For the transmission, ideally, if you're going to use a petroleum-based gear lube, you want an SAE80W90 or an SAE90 which meets GL4. Problem is most of what's on the market these days is "multipurpose"/GL5-rated. GL5 is actually a spec for lubricants used in rear axles. In short, for a four-speed manual, a GL5 will work, but a GL4 will make the trans shift nicer.

For best possible lubrication, if it were my car, I'd go to synthetics and, for an '81, I'd use Joe Gibbs Driven HR 10W30 in the engine and Gibbs Driven STF in your four-speed. The HR 10W30 engine oil has an appropriate level of of ZDDP additive to ensure durability of a flat tappet camshaft. The STF, is a synthetic equivalent of an SAE90 GL-4 gear lubricant.

Thanks, all. Chiltons specifically mentions GL5, and you definitely say GL4, Hib? I am now reading the bottle of 80W90. It reads as follows:
Differential: API SERVICE GL-4, GL-5
Non-Synchronized Manual Transmission: API Service GL-5
A bit confusing...any further clarification would be great - Thanks!!

 

[Antz81]

Thanks, all. Chiltons specifically mentions GL5, and you definitely say GL4, Hib? I am now reading the bottle of 80W90. It reads as follows:
Differential: API SERVICE GL-4, GL-5
Non-Synchronized Manual Transmission: API Service GL-5
A bit confusing...any further clarification would be great - Thanks!!

The FSM says to use GL5 as well. Hib does know a lot though. And there will be a good reason behind him saying to use GL4. Not sure what it is but would be interested to find out as I'll be due to change mine soon.
The valvoline you have would be GL5.

 

[kpic]

GL-5 is (not really) the latest gear oil. It has additives formulated for hypoid gears (aka ring and pinion) for high speed and/or low speed under high torque applications. That would include sun-planet and spur gear T-cases.
To be GL5, oil must be tested SAE J2360. J2360 is relatively new, it is a global requirement which includes GL5 and a MIL Spec.

GL4 is for spiral bevel and hypoid gears under moderate speeds and loads. It can be used in manual transmissions and trans-axle applications.

As it adds about 200-250K to the warranty, most commercial diesels have gone to synthetics for the manual transmissions.

The older GLs (1,2,3,and 6) have been dropped by SAE; I believed in the mid 1990s. Although a can may state the old numbers, there isn't any test standards maintained by SAE.

Shell Rotella-T is generally considered to be the best petroleum based engine oil. High or low load, high or low rpm. It is used in commercial diesel engines where the loads are much higher than seen by pass car or light duty diesels. No offense, but a 1 ton pick up is a light duty diesel.

I'm not a lubrication engineer, but I've worked with them.

 

[Hib Halverson]

GL5 lubricants are mainly for hypoid rear axle gears. Hypoid gear teeth rub across as well as mesh with each other. For that reason, a GL-5 lubricant will have a high proportion of extreme pressure (EP) additives.

GL4 lubricants are for the aforementioned light-load hypoids and spiral bevels but they are also for lubricating spur gear or helical gear transmissions. A GL-4 will have less EP additives.

The cone synchronizer rings in a Super T10, Muncie M20/21/22 or T10 four speed, need a certain level of friction to work properly and have good shift feel. While a GL-5 will certainly lubricate bearings, bushings and gears in a four speed manual, its high proportion of EP additives reduce friction so much it inhibits synchronizer action to a certain extent. Shift effort goes up because there is not enough friction between the synchro ring and it's cone and clutch.

I don't have an '81 Service Manual. It certainly possible a GL-5 is listed as a lubricant for the four-speed from that year, but a GL-4 will be a better choice. It provides all the lubrication the bearings, bushings and gears in those transmissions need along with the better shift feel from synchronizers which are working with the proper level of friction.

 

[kpic]

True and the only difference between hypoid and spiral bevel is the axis of the ring and pinion do not intersect. Which means it is a given that hypoid gear sets handle more load than spiral bevels. A hypoid gear mesh has a "sliding" action which dictates the need for the EP additives.

Another point, GL-5 has unfavorable effects on bronze components or you see yellow metal metal such as the synchronizers or bushings, do not use GL-5 unless the OEM specifically states it. So GL-5 is not necessarily backward compatible with GL-4. You'd need access to the OEM's material data to know and we will not get that access.

GL-5 can add viscous drag which is what affects shift feel.

Actually GL-5 has a lower coefficient of friction than GL-4; GL-5 might be too slippery. Synchronizers need a balance which GL-4 provides better than GL-5. Rather than get too deep, I did a search.

Red Line Gear Oils & Manual Transmission Fluids - Free Shipping on All Orders @ JEGS

Edit: Not a plug for Jegs, but my laziness.

 

[raybee]

Thanks again, all GL4 will be purchased this week.

 

[raybee]

OK, final question regarding the gear oil for the tranny in my 81. I just got the oil delivered by Summit. It's Brad Penn "Classic" Multi Purpose GL-4 80W90 Gear oil. All looks good with the exception of the following which is on the label: Not for use in applications requiring API GL-5 quality extreme pressure lubricants or where OEM specialized fluids are mandated.
Should this be a concern? Please let me know - thnx, Ray