Gear oil type?

My dad says the T18 trans in his 73 Ford truck calls for a heavy motor oil, not 90 wt gear oil:? My 74 cj has a Warner T18 4 speed trans. T18-1 to be spacific, I dont know the year or vintage. What is the recommended oil for this tranny?

 

i have always used 80w-90 or 85w-90

 

get a good gl4 oil. Novak-adapt recommends a good conventional oil, and also suggest a straight 50wt for faster shifting.

 

gl4 ?? You got me on that one. Can you elaborate?

 

The gear lube containers have this information on them. It's an API service specification. The auto makers will recommend a specific API recommendation for their particular tranny, transfer case, or differentials, such as API GL3, GL4, or GL5.

Some gear lubes will cover all of these specs.

I use 80-90 wt. in my t-18.

 

That helps. Thank you

 

Same here, 80W-90.

 

DO NOT USE any GL5 rated oils, they will wear the brass syncros. GL4 is what you want.

 

Thank you. The gear box does just fine now but when My pop mentioned that his FORD T18 called for 50 weight motor oil I was puzzled. I've always ran a 90 weight Hypoid in my older trucks.

 

There was a big discussion in here not long ago about this. Not all GL-5 oils are hard on yellow metals it turns out. I use GL-5 Valvoline or Napa (made by Valvoline) gear oil and have for years with no problems. The guys on this board told me there was something different about those brands.

 

I think I will stay with a 80w 90 just to be safe. Also with this cold weather country up here, it might be a wise choise.

 

I contacted ahsland Oil Co. (Valvoline) and asked them specifically whether their GL-5 formulations are harmfull to brass sychro blocking rings. Their reply was that baecause they use a non active sulfate, Valvoline GL-5 formulations are not harmful to yellow metals.

I've been using Valvoline GL-5 in my T-176 for years and have not experiienced at problems.

 

actually, the thick oil will not shift or flow as well in cold tempuratures. For cold climates, the 50w would be ideal.


Actually your BEST option is to get a dedicated Manual trans lube like BG syncroshift, Redline MTL or some other tyoe of manual trans specific lube.

 

My T-18 shifts just fine at 20 to 30 below zero. It's a little stiff for the first mile or so, but you'd never know the difference after that. I've been running this transmission for 11 years now. Ford recommends 80W-90 for all temps.

 

I'm not sure whats in it now. When winter starts I'm going to do a complete fluids change all the way around and will probabley go with the 80w 50. If it seems to sluggish at that point I my go with a lighter oil then. It gets down in the minus 10s up here but nothing like the winters back in the Mid West or North East, so I dont think it will call for drastic measures.

 

If you use a 75W-90 GL4 synthetic you will not need to worry about the cold and the oil being thick. That is one of the advantages of synthetic oil.