Hello,

I have a freshly rebuilt 4L60E in my Catalina that shifts very nicely but I have not gotten the transmission warmed up - very short test drives so far. When will I start to detect fluid flow out of the passenger side case ports? Is there a thermostat in the transmission that will eventually open up and allow fluid to flow or should I expect fluid to be flowing now when its cold?

My gut worry here is about potential leaks at those two case ports. I have none now but don't want a gusher to sprout when I begin to take longer test drives.

Rick

 

Fluid will flow out of the bottom case port through the cooler and back into the transmission through the top port. The fluid will flow as long as the engine is spinning over. This means that fluid is flowing as soon as the starter is cranking over and all the while the engine is running. There is no thermostat in a 4L60E that controls fluid flow.

 

Hello,

OK, thanks. Good to know.

Rick

 

Anytime vehicle is running,

 

Yep any time the engine is running. Cooler pressure is 30-60psi until lock up happens then it goes to 60-120psi

 

And in case any restrictions like bent rubber hose it can rise up to line pressure 200+ PSI at WOT and even more in reverse
There is no pressure release valve for oil cooler line (like some tranny has)
So avoid cheap tube type additional oil cooler - they rise pressure for no profit

 

To prevent case port leaks, be sure to use the correct threaded hose adapters. They are not tapered NPT !! They are straight thread which need a washer or o-ring. Hmmm- was there a switch some year between washers and o-rings?? (I'm forgetting details.)
In any case (pun intended), a tapered NPT will crack the port over time.

 

GM used 1/4" NTPS threads with sealant through 2007 on 4L60E, in 2008 and up the changed to an oring seal on the fittings. There were early P/G, TH350 & TH400 that had 1/4" NPT fittings and 1/4" NTPS with gaskets but were phased out for the sealant.