Scotty, I have a '79 Checker A11 Marathon with 82K miles with a 350 V8 and auto transmission...does not get driven enough and has developed a front and rear main seal leak. My mechanic advised to take to transmission shop for costly repair. Any thoughts on additives to stop leaks...thanks and look forward to hearing from you. Hank
Shouldn't be that big a job. The rear output shaft seal can be done in the vehicle. The front will require transmission removal but not disassembly unless it's the pump housing to case seal that's leaking. Hopefully the torque converter hub and the driveshaft input shaft are not worn. Make sure that the output shaft bushing isn't worn. This too can be replaced without removing the transmission.
additive should be an absolute last resort. If the motor/transmission isn't totally destroyed now, then it will be after you put additive in, and your rebuilder will hate you. If you are going to use it, I would only put half or quarter of a bottle.
It probably will need to be taken apart to replace seals, but since there's nothing to lose you could try the AT-205 Re-Seal polymer that Scotty recommends. It can help recondition seals as long as they are just a bit dried out but otherwise intact. (If the seals are worn out/cracking apart it won't help, of course.)
