Can't Find GL-4/GL-5 for Transaxle that Shifts OK

[Paul B.]

If the car manufacturer specifies 75w-90 GL-5 for the manual transaxle, I can't see why mobil 1 is going to do any harm. The syncro materials should be compatable with the additives if GL-5 is specified. Their may be other brands that have been found to work better with the syncos, but using a GL-4 formulation like pennzoil syncro will not provide protection to the differential gears that a GL-5 will.

 

[440Magnum]

Originally Posted By: Paul B.
If the car manufacturer specifies 75w-90 GL-5 for the manual transaxle, I can't see why mobil 1 is going to do any harm. The syncro materials should be compatable with the additives if GL-5 is specified. Their may be other brands that have been found to work better with the syncos, but using a GL-4 formulation like pennzoil syncro will not provide protection to the differential gears that a GL-5 will.


M1 may have some limited slip FM already added- which would defeat synchros even if the chemistry didn't physically damage them.

Also, most FWD transaxles do not have hypoid gears in the differential section like rear-drive differentials do. GL-5 is really for hypoid gears, not for "differential" gears. If the diffy gears are simple helical or straight-cut gears, then GL3 or 4 is adequate.

 

[Paul B.]

I'm using the Mobil 1 in a Subaru where GL-5 is called for. It did say it has an LS additive but it seems to work the same as the factory fill with regard to syncro action.(after 18,000 miles).
My point was that if the OEM calls for GL-5 you would not be using an oil that meets the requirement if you use a GL-4 even if you get better Synco action. Even if the gears are not true hypoid gears the factory likely had something in mind when they specified GL-5 for transaxle.

 

[bmwtechguy]

Well, your Subaru most likely DOES have hypoid gears in the transaxle differential since it is turning the front wheels with a RWD engine layout. In your case, I would prefer Redline 75W-90NS GL-5 gear oil over the M1. This particular flavor of Redline does NOT have the LS additives that are beneficial to limited slip differentials. This GL-5 Redline should help in a synchronized gearbox for faster synchro action and smoother shifts (in theory). You never know how it is going to shift until you try it.

 

[widman]

I told them it was not illegal to educate. Showed them copies of the Mitsubishi trans diagnosis manual where one of the first steps is drain the oil and put in a known GL-4, and the Nissan manual that specifically states you will ruin the trans with GL-5. They are idiots out for a buck.