My old Red Top in the 40 started making the same noise when I would charge it. Not long after that it wouldn't take a charge anymore. I've written off Optimas (at least Red Tops)...I've had 3 in my 40s and none have lasted more than 2-3 years. Granted, I'm pretty hard on them as the rig isn't run much so they sit idle alot.
Jeff Z. (the "not quite as skinny" one)
'97 FZJ80 Antique Sage AE #267, stock
12/74 FJ40, 2F, SM420, 4" Lift, ARBs, 33" MTRs
"...anything else i can do for you guys, how about i wash your car or mow your lawn while you figure out your firewall system? I am now boarderline insane/unibomber." Kipper
"That assumes I'm even capable of pulling and stabbing..." Jacket
"I really like having a detachable unit." Beater