Syncromesh

BSweet, would you check and see if Napa brand 80W90 is compatible with yellow metals (brass and the like).

I'll step out here without personal experience, but what I've gathered from EarlyCJ5, as well as other sources, GL - 4 is the recommended rating for, shall we say, "classic" synchromesh transmissions. I'm understanding that GL- 4 is right for brass synchronizers, and that is GL - 4 specifically, not GL- 4 included in combination with other ratings such GL- 5.

 

They opened a Tractor Supply by me, I love it, I am amazed by what they have there. It is worth going to just to look around.

 

I used Napa 75-210. GL3,GL4 and GL5 API rated. Says it is for use in manual transmissions and axles. I think it was better than the 50 year old looking stuff that I drained out of everything. Had to literally scrape the old gear oil out of front differential!

 

That's fine for the differentials and transfer case but not for the transmission. The GL-5 rated stuff is not good for these old transmissions. You want the GL-4 rated stuff.

 

I suppose that's why I have about 4 gallons of it out in my garage. It took me a few years to catch onto the difference between GL5 and GL4. The guy at NAPA thought I was nuts. I had to explain it to him. I'm sure he still thinks I'm nutso.

 

Yeah, I went through this same issue with a couple local auto parts houses. I gave up and just ordered it from amazon.

 

I will see if I can get anything that is straight GL4 rated. I work at a Napa store myself!

 

I just bought five quarts from Napa three or four weeks ago. Sta-Lube it is called. GL 4

 

Never thought of Sta-Lube brand.

 

me neither, but it seems to be the only available one making GL-4

 

Its not cheap, paid 36 about 3 weeks ago.

 

Apparently Redline MT-90 is another good option, if you want to go the synthetic route. And pay the synthetic prices.

 

I haven't tried the Redline but I've had bad experiences with other synthetics in a transmission that requires GL-4. Caused all kinds of hard shifting and grinding issues. Too slick for the blocking rings to cut through the oil film and grab the cone of the gear like it needs to do for proper shifting. This is one of the problems with using GL-5 in these transmissions.

 

5 quarts of Sta-lube was over $50.00, but at least I got what I was advised to use by the people that know on this site.

 

There's a Motorcraft full synthetic 75W90 full synthetic oil that's GL-4 rated. I tried it in my T-90 and it behaved much as you describe.
Switched back to the StaLube GL-4 dino oil and no problems....

 

All this talk of oils has me wondering..... is the problem that it will grind going into 2nd or 3rd, or is it a problem that it will pop out of 2nd or 3rd gear?

 

Too slick will make it grind. The brass blocking rings have to grab into the gears so that gear speed matches. No matching makes gear clash.

I expect it will not effect whether the transmission stays in gear or not. That's more about the transmission parts being worn out, or not.

There is also a chemical compatibility issue, something about the sulfur in the oil affecting the brass blocking rings.

 

I have only put maybe 50 miles on mine since putting in the Napa stuff. I haven't noticed any difference in shifting yet. I seem to grind the shift 2nd to 3rd every now and then. Did it before changing trans oil too. I think it is just my bad habit.

 

If it will hurt something in the trans then I will change it back to a GL4.