Oil suggestions needed

I need to put oil in the Xm211 and the manual transmission that was put in to replace
the old automatic one. What type of oil should I use for both the engine and the transmission.

I figure that since the engine is old it way need a different spec than what was originally
called out.

Thanks for any input on this.

Discussing oil is like religion, no one ever agrees. I would run normal gear lube in the tranny. I would fill the engine with straight 30 in the summer and 15-40 in the winter.

JasonS is right....everyone has a different spin. For example. The engine; High mileage 10w40 is a good choice for year round use. The tranny; 80w90 or there abouts would be fine. I, by no means am saying I know what's best. I can say I have owned and operated around 15 of the old GMC Hydro's over the years. I still have one.

Thanks guys,
That really helps a lot!

youre living in ca ... and its a high milagae unit . i would suggest straight 40wt. non detergent.

it calls out for 30wt. nd oil but if it has a bunch of miles or low oil pressure i would go with the 40 wt.

What would you guy's recommend for the Hydro Transmission? I have heard several things - Dextron, Tractor hydro fluid...

The previous owner put the tractor hydro transmission fluid in it. Is this going to be OK or should I change it ASAP?

The main thing is to put in NON DETERGENT Oil. I buy mine from a local tractor supply store. The modern oils have a detergent additive to them, but older engines should use non detergent. I'm not sure what the main difference is on the engine side, but that is what several mechanics have told me. I think it was actually cheaper too.