My former G20, now owned in California by a friend, is getting a new clutch tomorrow. I was telling him some things to be aware of (to mention to the mechanic, really, since he is not the faintest car person) and I cannot remember whether GL-5 is OK for the trans in those cars. I remember that the service manual calls for GL-4 - I'm certain this is correct. I also remember that GL-5 may be bad for the synchros in the long run, but I'm not certain of that. I also remember that when I replaced the engine in the car years ago I absolutely could not find GL-4 anywhere, and ended up using Castroil Hypoid C, which was GL-5 and obviously worked OK since it was in there for ~80k miles and it always shifted great. Is the correct weight of GL-5 oil OK for the trans? I might have put Redline MT90 in there a few years ago (I can't remember!) but this is not a situation where anyone is going to be putting Redline in there.<div>
<br></div><div>thanks,</div><div>David</div><div>Chicago</div>