Transmission Fluid

[september2021]

On my '76 MGB non overdrive I have been mistakenly using 80/90 weight gear oil in the transmission instead of 20/50 mineral oil.

I've driven like this for many years.

I will change it out to 20/50.

My question is

Is there any damage done by using the incorrect weight oil?
Would there be a reason to totally flush out the 80/90 ?
How would I go about rectifying this.

Thank you for your time. Best wishes

Aron Sokol

[JohnTwist]

Any oil is better than no oil; 20/50 or 30 weight non-detergent engine oils are the best oils.  In my days at the shop we’ve drained out:  Automatic Transmission fluid (red); 80/90 gear oil; water and oil; and every now and then no oil at all. 

The TR6s use 80/90 and sometimes we would use 80/90 in a noisy Midget box.  You’ll be OK. 

Use the 80/90 in the differential, rack and pinion, and in the carb damper(s).

SAFETY FAST!
John H Twist
University Motors Online
100 East Beltline Avenue SE
Grand Rapids MI 49506-2410
Cell  616 307 6737
www.universitymotorsltd.com