I know this subject has been talked about.... but i just had my trans gear oil changed and decided to put conventional gear oil in. I noticed the mechanic put in Castrol Hypoy C 80w 90. It has a GL5 rating, I was thinking that i read that a GL5 rating was not applicaple for my 1983 308... any input would ge appreciated.. Mario
It's fine. Your thinking about a thread where it was assumed that the syncro's were brass, which they aren't.
It's not specifically required for your 308 gearbox (since the 308 design doesn't have a hypoid gear set inside which has sliding, as well as rolling, action in its tooth meshing action -- those designs need a GL5 rated oil), but many of us have used GL5 rated oils in 308 gearboxes and reported good results as matteo indicated.
I have also added a gear lube additive that chevy sells. It's about $7.00 and comes in a small tube. Two tubes works the best. Also, redline and royal purple are pretty good as well.
Matteo, what about the gearbox of the 1975 GT4? The Agip Rotra MP SAE 90 is no longer available, have put GL5 80W90 EP ( Extrem Pressure ) but I am not sure it works, felt some reluctancy in engaging the reverse gear (in hot conditions ). I am waiting to get some Castrol or AGIP Rotra LSX 75W90 full sint oil which should work ,any advice?
I got the Chevy additive advice from a owner of a GT4. He was on the board for a long time. Hans Hansen. He started the whole debate about GL5, which transmission oil, limited slip additives about 4 years ago. He was running straight 80/90 with the chevy limited slip additive and he said it shifted like butter. I followed his advice on my old 78 and continued on my 83.
at the risk of starting yet another tangent, has anyone tried slick 50 it seems to fufill all the necessary critiera. got some today to try next week. will advise.
the GM limited slipadd is vg.also royal purple. another product is made by BG LSll really helps with the clutches.red line makes and entreme pressure lude that has been helpful with the second gear issue. forza fmaderi im using a friends computer
I've currently got Valvoline in my car and it works fine. Shifts easily into second as long as the temp is about 40 degrees. This stuff is cheap and easy to find.
