Gear oil for the T221 and SM465

[vectorit]

I was at Napa AP today to get more oil, you know the standard 80/95 for the Tcase/trans/axles. I saw the Royal Purple stuff, and what caught my eyes were the wt ratings 80/145 or something.

I'm interested in this stuff only because of the viscosity rating at this point.

The price was the same as the regular lube I get.

Mainly interested in this heavier weight gear oil because of the excessive heat I go through here in the summer time, since during the summer the 80/90 stuff turns to a very thin oil and everything gets louder and the Swiss watch like machined surfaces of the trans/tcase leak like a sieve.

Just wanted to hear any positive/negative comments.

[Stocker]

When I was young (and before all this pesky multi-grade stuff), I was told 90 weight for cars & light trucks, 140 for medium & heavy trucks. Having said that, our old '95 ZJ called for 75W-140 in the D35 rear diff (with tow package).

Just guessing the 140 rating is more for extreme pressure of heavy loads, not so much for heat. I would think you'd be fine with synthetic 75W-90... and if it leaks, 140 weight would probably leak also, maybe just a bit more slowly.

[maxwoof]

My experience is that thicker oil will not stop the leaks. It may be more quiet though. I have had engine oil leaks develop upon switching to synthetic.

My feeling is that the only way to stop the leaks int the t-221 (which is notorious for leaks) is to remove all the bearing carriers/shims, coat them with sticky black liquid permatex and reinstall. Need to coat the bolt threads too.

I don't think the higher viscosity oil will hurt any, though, and may be beneficial, as I have heard these cases run hot.

I am running straight 80w-90 from agri-supply in my '62. Both in the trans and transfer case. Leaks aside, seems to be OK.

[Redcap]

Fix your seals.

I run standard old 80/90w.