gear oil GL4 or GL5

[tonkatoy189]

i recently canged all the gear oil (difs, trany and transfer) my 64 rover. being too smart to use instructions, i did it with the gear oil i use in my alfa romeo. of course in reading the manual after the fact i noticed that the oil called for in the rover is GL4 and i put in GL5. i used 90w as per the book. am i doing any damage running with this oil? whats the diffrence between GL4 and GL5 anyway?
thanks
david

[slouzon]

Originally Posted by tonkatoy189

i recently canged all the gear oil (difs, trany and transfer) my 64 rover. being too smart to use instructions, i did it with the gear oil i use in my alfa romeo. of course in reading the manual after the fact i noticed that the oil called for in the rover is GL4 and i put in GL5. i used 90w as per the book. am i doing any damage running with this oil? whats the diffrence between GL4 and GL5 anyway?
thanks
david

The way I understand it is that GL-5 has additives that can attack the soft metal parts like synchros.

I wanted to run synthetic, I have always used Mobil 1 as it is available everywhere. But it is not recommended for GL-4 applications.
So I have given Royal Purple MaxGear 75W90 a try.
Seems to be doing OK so far but it's only been 2 weeks on as freshly rebuilt trans.

[pickuprover]

OH the long and lengthy debate about gl4 is restarting....

GL5 yes has sdditives that can eat the brass in your tranny (it is fine for everything else as there is not any brass in the diffs....) My thoughts... the rate at which the GL5 will eat the brass is very low, and chances are you will be rebuilding the tranny before the syncros go. As well as the only brass that is in the tranny is the syncros, if they do get eroded, well then you just have to double clutch 3 and 4 as well. If you can find gl4 (I was lucky and have found a source in Ontario at a resonable price) then of course use it. As well there are some gl5 oils that state on the packaging that they are yellow metal safe (but they usually carry a hefty price tag...)

[slouzon]

I agree.
But I was using synthetic anyway and the cost difference between the Mobil 1 GL-5 and the Royal Purple GL-4 safe was a no brainer.

[tonkatoy189]

thanks for the info. i'll probably change the tranny oil at some point this summer. i've heard that synthetic oil is better at finding those leak holes than good old dinosaur oil. the folks on the alfa BB said that on a fresh rebuild with all new seals it is fine. but to replace petroleum oil wthh synth is asking for leaks.
later
dk

[slouzon]

Originally Posted by tonkatoy189

thanks for the info. i'll probably change the tranny oil at some point this summer. i've heard that synthetic oil is better at finding those leak holes than good old dinosaur oil. the folks on the alfa BB said that on a fresh rebuild with all new seals it is fine. but to replace petroleum oil wthh synth is asking for leaks.
later
dk

Can you say "wives tail"?

Synthetic oils don't thicken up as much at cold temperatures so they will continue to leak.
If there are leaks there are leaks bottom line.

Remember when they said you couldn't put synthetic in a new engine until after 8000 miles or it would never seat the piston rings?
There are a lot of cars coming from the factory with synthetic now.

I wouldn't put synthetic oil in a leaky box just because it cost to much to pour it on the ground.

[Disco Mike]

Not to confuse the issue of the GL4 and GL5, but what do you guys heart about the GL6? I have been running it for nearl 5 years in my diffs and t/case, started using it when I found it took all the noise out of my Detroit.
In my vehicle I am running their 85/140W for the extra wear protection and it's ability to withstand more stress.
Mike

[jimfoo]

Originally Posted by slouzon

Can you say "wives tail"?

Remember when they said you couldn't put synthetic in a new engine until after 8000 miles or it would never seat the piston rings?
There are a lot of cars coming from the factory with synthetic now.

I wouldn't put synthetic oil in a leaky box just because it cost to much to pour it

I believe I heard that those engines were broken in at the factory. After running it in my race car and seeing how much better it protects than conventional, I would NEVER break an engine in on synthetic.

[slouzon]

No been to a couple of the plants making the engines for a few different manufactures and they do put it in straight from the factory.
But I do believe there maybe other things done to help with compression ring seating like special materials on the ring wear surface.
I also know there have also been changes to honing processes for the cylinder bores, i.e. peak honing but these changes I believe were made mostly to reduce oil consumption over the life of the engine?

[jimfoo]

Originally Posted by slouzon

No been to a couple of the plants making the engines for a few different manufactures and they do put it in straight from the factory.
But I do believe there maybe other things done to help with compression ring seating like special materials on the ring wear surface.
I also know there have also been changes to honing processes for the cylinder bores, i.e. peak honing but these changes I believe were made mostly to reduce oil consumption over the life of the engine?

Yeah, basically it looks like cylinder finish. Mobile says ok to use, Redline says no. My take on it is if I have to be changing the oil soon, why do I want to spend twice as much on it to break it in. I do like synthetic, at least if whatever it's in doesn't leak.
"
Many readers have questioned us on engine break-in procedures when using synthetic oil. Conventional wisdom has it that a new or freshly rebuilt engine should be broken in using mineral oil, then, once enough mileage has accumulated to ensure rings and cylinder walls have lapped themselves into harmony, synthetic oil can be used.

Readers have correctly pointed out that several major brands come from the factory with synthetic oil, among these being Corvette, Mercedes-Benz and Viper. How can these engines break-in if run on synthetic oil from day one, they ask?

To find out, we spoke with Mobil and Redline Oil companies for their take on the synthetic break-in question. Mobil's response was that engines break-in just fine on synthetics, and that any wear point in the engine significant enough to be an interference, and thus susceptible to rapid wear, would be a wear point no matter what lubricant is used.

Redline, on the other hand, has found it best to recommend a mineral oil break-in. Occasionally an engine will glaze its cylinder walls when initially run on Redline, they say, so by using a mineral oil for 2000 miles, verifying there is no oil consumption and then switching to the synthetic, glazing is eliminated.

Cylinder-wall glazing is not a deposit left on the cylinder wall, but rather a displacement of cylinder-wall metal. This happens when the high spots of the cylinder wall crosshatch are not cut or worn off by the piston rings, but rather rolled over into the valleys or grooves of the crosshatch. This leaves a surface that oil adheres to poorly, against which the rings cannot seal well. Compression is lost and oil consumed, and the only cure is to tear down the engine to physically restore the cylinder-wall finish by honing.

Why is glazing not a problem for the major manufacturer? Because they have complete, accurate control over their cylinder-wall finish and ring type. Redline deals with a huge variety of engines and manufacturers, both OEM and from the aftermarket. Cylinder-wall finish and ring type thus vary greatly, and glazing can therefore occur, albeit rarely."

[jimfoo]

Back to the original topic... Viscosity wise, 30 wt engine oil is the same as SAE90. They are rated by two different systems. I think I have heard rumors of people using 30 wt in their gearboxes as they don't have the yellow metal eating stuff in them. Anyone have first hand experience with this? Also, the synchros aren't the only yellow metal, there is the bushing which is I think between 2nd and 3rd gears, the two piece one, or one piece which would turn itself into a two piece.

[MPi-KMS-72]

Originally Posted by jimfoo

Back to the original topic... Viscosity wise, 30 wt engine oil is the same as SAE90. They are rated by two different systems. I think I have heard rumors of people using 30 wt in their gearboxes as they don't have the yellow metal eating stuff in them. Anyone have first hand experience with this? Also, the synchros aren't the only yellow metal, there is the bushing which is I think between 2nd and 3rd gears, the two piece one, or one piece which would turn itself into a two piece.

I've done the 30wt trick in a vintage Volvo for those reasons. it went 100k+ on that 30wt with no issues.