Manual Transmission Oil

I have a 16' TRD 4x4.
Its about that time to change some of my fluids so I went to a local shop to pick up some oil for my differentials and manual transmission. They said Lucas 75w90 will work for everything. I sent off an email to Lucas to see if this oil will work because our manual book says to put in GL-3 (GL-4) or equivalent. I decided, the local shop should know what they're talking about (I questioned him and he read the information off his screen) and on the bottle it says "Trans & Diff Lube" and on the back it says exceeds API GL-4 and API GL-5 ratings. so I just went with that and changed all the oils.

Lucas finally got back to me and said that oil will NOT work with the manual transmissions (false advertising????) but will be fine in the differentials. At this point I already changed my M/T fluid with the Lucas.... so now i'm on the fence of draining it and buying Redline MT90.

What do you guys think? Has anyone used this lucas oil in their transmission and everything was okay? I'll definitely be switching to Redline MT90 on my next change if the lucas is fine in there for the next 30k

 

Redline MT90 is super popular among many MT owners in all makes of vehicles along with their gear oil. I'm running all their fluids, even the D6 ATF in an auto car.

Forgot to add, don't know about the lucas. But, GL5 gear oils have added sulfur that can mess with soft metal syncros in MTs. It's only 3qts, I'd drain it and put in the RL.

 

I would drain it if it was me. Lucas is telling you that it will not work. Drain it and move on.

 

Like stated, syncros. There's a reason to skip GL-5 and slippery fluids in syncromesh transmissions. I run MT-90 in mine and it's fine. 75w-85 GL-5 in the diffs and MT-LV in the transfer case (again, a syncro).