Ok, so let me start off by saying that I'm not trying to be shady and hide problems here. I deal with a very low income, high-risk customer and need to perform repairs as cheaply as possible in order to keep things within their budget otherwise they're walking (literally). The backstory is that I had a customer who wrecked their LeSabre a month after we put a $1,500 transmission rebuild into it. I kept the salvage because I knew it had a new transmisssion. Recently, I pulled that transmission to put into another car and come to find out after the fact, the case is cracked at or around one or more of the threaded mount holes (presumably from the wreck). I have epoxied and silicone'd the damn thing to hell and back and it still seeps just a little bit when warmed up. It's not a pressure leak, just leaking from the side case a little bit presumably when the fluid level gets above the crack. Not a bad leak, just a steady drip.
Point of the story is, I really don't want to throw away a $1,500 transmission due to some simple problem like this. I have verified I can "fix" it by running a vacuum line to the transmission vent. I used a clear hose at first to verify that it does not actually suck any fluid out of the trans. All is good. I've used this trick on oil leaks a lot in the past by installing a check valve in the vent line of a PCV system to actually build crankcase vacuum. Works wonders for worn VSS and pan/other crankcase seal leaks. Effectively, it turns a fluid leak to the atmosphere into a vacuum leak, which can be more easily compensated for.
So basically, the problem is that often if you do have a leak, and you draw full manifold vacuum, the leak will go to squeaking/squealing badly (almost sounds like a bad pulley bearing on the belt). I can solve this problem with an adjustable check valve/vacuum regulator, and in fact did just that by going to the hardware store today. All is well. The problem is, the damn thing cost around $25 in parts/fittings to make. Still much more cost effective than finding them another transmission, but not something I would want to spend in every case. I would love to figure out how to build or buy something that would create a couple PSI (or preferably adjustable) pressure differential between the vacuum source and the target (trans or crankcase) that cost more like $10 in parts, not $20-30. Ideas?
Am I dumb and overthinking it again?
Point of the story is, I really don't want to throw away a $1,500 transmission due to some simple problem like this. I have verified I can "fix" it by running a vacuum line to the transmission vent. I used a clear hose at first to verify that it does not actually suck any fluid out of the trans. All is good. I've used this trick on oil leaks a lot in the past by installing a check valve in the vent line of a PCV system to actually build crankcase vacuum. Works wonders for worn VSS and pan/other crankcase seal leaks. Effectively, it turns a fluid leak to the atmosphere into a vacuum leak, which can be more easily compensated for.
So basically, the problem is that often if you do have a leak, and you draw full manifold vacuum, the leak will go to squeaking/squealing badly (almost sounds like a bad pulley bearing on the belt). I can solve this problem with an adjustable check valve/vacuum regulator, and in fact did just that by going to the hardware store today. All is well. The problem is, the damn thing cost around $25 in parts/fittings to make. Still much more cost effective than finding them another transmission, but not something I would want to spend in every case. I would love to figure out how to build or buy something that would create a couple PSI (or preferably adjustable) pressure differential between the vacuum source and the target (trans or crankcase) that cost more like $10 in parts, not $20-30. Ideas?
Am I dumb and overthinking it again?