G56 fluid ?

[Newsa]

Mine is quiet. So I see no need to put anything heavier (more viscous) than 75w 90.

I just thought it curious that a synthetic oil manufacturer was recommending mixing weights. Especially since GL5 fluids are known to be harsh on synchros.

I will stay with the DMF. And will have it checked (possibly replaced) when my clutch goes. I haven't been towing heavy enough lately to rrequire a more stout flywheel/clutch set up.

I think ATF is adequate. But I doubt It's lubrication qualities can match a real manual transmission lube. ATF has lube qualities, but was designed to transfer loads (fluid pressure) in addition to lubricaring. After my max care expires (only have about 7 months left on the Power train warranty, but have 2 1/2 years left on the max care), I plan to change to redline mt-90. It is a top quality 75w 90 transmission lube.

I often use amsoil products. But I think redline is much better. And if I'm going to leave it in there a couple of years (just top off when needed), I want a good lube in there.

 

[Randomrunner12]

RVTRKN and I have spoken many a times on the matter of fluid and after so i went with the Mobil delvac 7qts. I will eventually build his cooling setup and I still have the files for it and am sure it will help me in the future.

 

[Newsa]

The gear ratios were a lot higher making it easier on the trans as well as a higher ratio diff. They are medium duty trucks they went into. However they changed ratios for the CTD, to make it more acceptable to our graphics and market. So the trans runs hotter with a 50wt oil. The ATF has been used in the past for manuals and sheds the heat better, as well as doesn't attack the brass syncros, they thought they were doing good. End of the day if you run a heavy weight oil, monitor the temps.

"Doesn't attack the brass synchros".....

Yeah, I know that a gl5 gear oil is not recommended in most manual transmissuons. But gl4 gear oils are "designed for" manual transmissions.

Both gl4 and gl5 oils have extreme pressure additives. Gl5 has about double the extreme pressure additives that gl4 does. So, I'm guessing it really is just the "concentration" of extreme pressure additives that is the concern with using gl5 lubricants.

FCA recommends the use of ATF4+ fluid. Is this because there are no extreme pressure additives? ATF4+ does have antiwear additives (but these don't attack alloys like brass/bronze).

Well, I will be switching from ATF to Redline MT-90 next month. I like the Redline line of lubricants. Their ester synthetic base is suppoed to adhere to the metal like the extreme pressure additives. So, I hope they use a lower concentration of EP additives because their base oil already has some of the characterisitcs that the additives are supposed to have.

Long live the synchros!