MGB transmission oil recomendations

[WKLINNC]

Hello,

I'm new to this forum and have found a ton of great info - Thanks!
Would anyone have a recommendation on what would be the best choice for trans oil for my newly rebuilt '70 B trans? I have seen everything from staight 30W to 10W-30 to 20W-50. What if anything has anyone heard about using synthetics or semi-synthetics? I always thought a slightly lower viscosity would help out with those sluggish shifting cold mornings.

Thanks -

[CraigFL]

Most die hard MGB owners would put Castrol 20W-50 GTX oil in the transmission especially if it's an overdrive version. I personally use Redline synthetic -- MT90. You should be careful what you put in because there is significant bronze/brass bearings in either transmission that could be damaged by any GL-5 type gear lube.

P.S. The owners/workshop manual recommends 20W-50 or 90 weight Hypoid. You do have to be careful with modern 90W Hypoid because much of it is manufactured to GL-5 specifications and shouldn't be used.

[KimMG]

Castrol 20W-50 GTX is what I use in the original transmission and motor with 150,000 miles on them. I change the oil in both every 3 to 4 thousand miles.