I'll chime in again. Shortly after I got it, I drained the 4-sp manual trans on my Volvo & refilled with Mystic gear oil. This would have been sometime in late 75-early 76. Kept Mystic in the trans for the rest of the time I had it. Was still smooth shifting, reliable, no transmission problems at all when I sold the car in fall '97.
IMO, Mystic gear oil was & is a *great* product. The oil field trucking yard where I worked back then used it in every gearbox & diff they had, & problems with those units were almost nil.
I just ran the rear end with what came in it for years.
Finally in ~82-83 I bought a suction gun & got all the old diff oil out possible with that method. Refilled with some dino gear oil that claimed suitability for hypoid applications. A couple of years later I pulled that out & refilled with Mystic. It was getting a slight whine at highway speeds, that disappeared within 50 miles & never returned!
No problems, no leaks, was on its second Mystic fill when sold in 97.
Volvo used at least 2 different rear axles on those cars, maybe 3 or 4. I can't remember all the makers now. And IIRC, the station wagons were geared lower than the sedans. Going from memory: About 4.10:1 for the sedans, maybe ~4.56:1 for station wagons.
I strongly suspect your Volvo has a regular open diff, & not a limited slip. I know mine did. I believe mine also had the Spicer rear end, but woudn't swear to it.
If I had your car: I'd use any good 70/75w80/90 gear oil in the trans, & Schaeffer or Mystic would be my top two picks. If Schaeffer says their product is suitable for hypoid applications, I would be delighted to put it in the rear end also. I know Mystic will work fine. And the Mystic is very pretty stuff: looks like Cherry or Strawberry snow cone syrup.
These days you usually have to read the fine print on a gear oil for hypoid sutability. Many of them are, & I suspect this is an area that's improved a great deal since the 1950's & '60's when those cars were designed & made.
Good luck, & let us know what you use!
IMO, Mystic gear oil was & is a *great* product. The oil field trucking yard where I worked back then used it in every gearbox & diff they had, & problems with those units were almost nil.
I just ran the rear end with what came in it for years.
Volvo used at least 2 different rear axles on those cars, maybe 3 or 4. I can't remember all the makers now. And IIRC, the station wagons were geared lower than the sedans. Going from memory: About 4.10:1 for the sedans, maybe ~4.56:1 for station wagons.
I strongly suspect your Volvo has a regular open diff, & not a limited slip. I know mine did. I believe mine also had the Spicer rear end, but woudn't swear to it.
If I had your car: I'd use any good 70/75w80/90 gear oil in the trans, & Schaeffer or Mystic would be my top two picks. If Schaeffer says their product is suitable for hypoid applications, I would be delighted to put it in the rear end also. I know Mystic will work fine. And the Mystic is very pretty stuff: looks like Cherry or Strawberry snow cone syrup.
These days you usually have to read the fine print on a gear oil for hypoid sutability. Many of them are, & I suspect this is an area that's improved a great deal since the 1950's & '60's when those cars were designed & made.
Good luck, & let us know what you use!
