Trans fluid leak suspect cooler location problem.
 

Last week I got the truck running again. Topped off the trans fluid to cold mark and ran it for about an hour charging the ac, etc. Pulled it into the garage and did not look at it all week. Went out today and there is a puddle of trans fluid equal to about half a quart spread across the shop floor. First blush looked to be coming from front of trans pan or flywheel cover. I suspected at first the pan was leaking or front tranny seal. I checked the trans fluid and it was a pint OVER the hot mark. Pulled the flywheel cover everything is dry inside so not a seal issue. Looked at the pan then found fluid on top of the trans at the fill tube.

Light bulb goes off. Trans cooler and lines are higher than the fittings in the trans and when I checked the fluid the truck was running. Let it sit and the tranny cooler and lines siphon back into the trans and fluid came out of where the fill tube goes into the trans. Just backed the truck out of the garage under power and no leaks and the fluid level now reads 1 pint low. That tells me my cooler (photo attached) and line hold about 2-3 pints, its a big cooler from an old pop machine.

So question is can I put upward loops in the rubber lines from the cooler to transmission higher than the cooler to act as a air gap to keep it from draining back into the trans. I am not a trans guru but think the way the circuit works is one line is under pressure to push hot fluid thru the cooler and back to the trans were it falls under gravity into the pan. Looping the hoses will create an air pocket but will the pump just push it into the trans which is atmospherically vented when I start the engine. OR is the whole loop pressurized and will I be pushing air into places it should not be?

Also I am running a deeper trans pan and pickup that adds two quart capacity so I am not too worried about being a pint, about 1/4" , low in the pan. Maybe I should not worry about it??

update, drove it around the block, trans is working fine.

Thanks in advance.

Re: Trans fluid leak suspect cooler location problem.
 

That's worth a try.

With a leak like that I usually try to clean the area I suspect the leak to be off real good so it is clean and dry and then run the rig or drive it a short way and inspect the area to see if anything leaked.

Back in 1981/82 when I put the 48 together with the 350 and turbo 400 in it I had one of those Pepsi case cooler condensers for a trans cooler (found the cooler on the side of the irrigation canal where the canal workers had set it with what ever machine they were cleaning the canal out with. Had the coin box busted out and the pop missing. Anyhow I still pack scars on my left arm from slipping on some spilled fluids and falling against the front of the truck before I put the grill and front panel in. It did work good on a road trip to
Texas and back and a trip to Ogden and back the next year.

Re: Trans fluid leak suspect cooler location problem.
 

Thanks for the reply. The cooler has always worked well. Before I had it in front of the radiator and ran rubber hoses back to the trans with out any issues.

Re: Trans fluid leak suspect cooler location problem.
 

most oem trans coolers are higher than the trans as they are vertical in a cross flow radiator
basic hydraulic theory prevents siphoning as one side will be blocked by a valve or pump
unless you have an air leak you can have no air gap, fluid will push any air out of the lines

you didn't driver the truck other than in/out of the garage to bleed all the air out of valving and clutches
at this point i wouldn't worry about it

Re: Trans fluid leak suspect cooler location problem.
 

First time just in and out, the other day around the block a couple of time. Engine got up to operating temp, but trans only to about 120 degrees and was shifting fine. I will keep track of it and address later if I start having issues. Thanks for the reassurance.