View Full Version : TR2/3/3A TR3 Rear End Oil (Again)

Mickey Richaud
06-26-2005, 10:56 AM
OK - I should know this, but have to ask: Is synthetic oil safe to use in differentials? Can't seem to find Hypoid oil locally, and I need to change mine out (I'm afraid it's got some GL-5 in it - hope there's no damage).


Geo Hahn
06-26-2005, 02:11 PM
And maybe someone can refresh my memory... what is in a TR3 diff that would be harmed by GL5?

Dave Russell
06-26-2005, 07:23 PM
Hi Geo & Mickey,
Nothing in the rear end, that I am aware of, would be harmed by use of GL-5. Since it IS hypoid, it could well benefit from using GL-5. It's just not such a good idea in transmissions with brass synchronizer rings.

GL-4 & GL-5 are specifications. Both synthetics & non-synthetics are available in either rating. GL-5 has more sulfur additives in it which help it resist the very high sliding pressures that occur with hypoid gears. As mentioned, the high sulfur content of GL-5 is thought to degrade brass components in transmissions.

Likely, it would take years for GL-5 to actually damage brass transmission parts, but why take a chance?

Mickey Richaud
06-26-2005, 09:26 PM
Thanks, Dave.

So, since the factory specs call for 30W for the gearbox, any good motor oil is fine there (I intend to use Castrol 20W5 when I change it out). The differential should have GL-5.

Sorry about the confusion, but I was looking at an earlier post, and got some conflicting information (imagine that!)

Thanks again,

Geo Hahn
06-26-2005, 10:09 PM
FWIW our local Checker Auto Parts (may be Kragen or Schucks in Tenn) regularly carries Castrol GL5 in shorts & quarts.

Mickey Richaud
06-26-2005, 10:30 PM
Thanks, Geo, but we don't have either of them here. And any Castrol product other than motor oil is hard to find here. No matter, though, as I may be going with synthetic for the diff. anyway.