OK so I have been doing a little research here and have not really found the answer I am looking for. Wondering if someone with more experience with this would be so kind as to help me out. I have lucas sae 80W-90 heavy duty trans and diff lube. It says exceeds service level for api GL 4, GL5, MT-1, sae j2360, Mack GO-J, and pg-2 limited slip. I am wanting to change the trans and rear end gear oil in my 86 4speed manual and rear end oil and have never done this before. This is the one ton dually rear end. Advance auto showed the gl4 or gl5 80w-90 for both the trans and rear end? I am wanting to make double sure I will be ok using this lucas in both the trans and and rear end. Dont think it has ever been change at 95,000 miles. Want to be sure I am do the right thing as we are about to drive this little Toyota Bandit motor home from Va to Baja Mexico and back! Thanks for your input, Jay

 

ONLY Put GL-4 in the tranny. GL-5 is too slippery and it wont shift well from what ive read. it will do good in the rear end though

 

I guess this is what has me confused as it says it meets or exceeds manufacturer specs for both gl4 and gl5? Thinking I might need to get GL4 specific for the trans?

 

I wouldn't use any lucas products.

I went with mobil gear oil in all cases and diffs.

 

^^^^^^x 1000^^^^^^ i could not agree more

 

Well I already have this Lucas and am thinking I will use it in the rear end only and go with some gl4 specific gear oil for the trans. I read on another post that someone had been using the lucas 80-90 in their rear end for a long time with no problems. Any specifics why you guys dont like lucas products as I have always heard pretty good things about them? I am getting some shudder when at lower rpms in third and fourth hoping a gear oil change will help this. I have given the u joints a good push pull and tug trying to feel any play and I feel none?