4L60E diagnosis

[redhotrod]

Ok guys, searched all over the internet and can't find any reasons why my 97 chevy 1/2 ton 4x4 pickup transmission is making some strange rattling sound in the tranny pan at all times, P NRD321, and gets louder with rpm, especially P or N. Does not slip yet, still shifts gears fine, fluid looks and smells ok, just afraid it might let loose soon.

 

[Larry J]

Being a 4X4 it could be something in the trans or transfercase, like a shift fork or converter, or pump problem. But if your doing it yourself you should check stuff like bellhousing and transfercase bolts first. Then you should use a stethoscope to "try" and further diagnose before you pull anything apart.

But if your like most people or even most mechanics, you should take it to someone your going to have do the work for diagnosis, and put the onus on them. Never go into a shop and say overhaul the trans it's making noise, because it won't be on them if that's not where it comes from. Tell them it needs diagnosed and get an estimate for the next step..
Larry

 

[redhotrod]

Last night I climbed under the truck while it was running and listened closely to where the rattling was coming from and it seems like I most likely have a cracked flexplate. It doesn't sound like it is in the tranny pan or pump, but in front of the converter and behind the oil pan. Plus, not sure if this is a true sign of a broken flexplate is I can sit there and watch underneath using the starter as a guide, the flexplate has almost a 1/8" runout

 

[Chuck Leeper]

"I can sit there and watch underneath using the starter as a guide, the flexplate has almost a 1/8" runout"
Hopefully, it's the plate and not the thrust brg!

 

[redhotrod]

Me too! But I am pretty sure it has to be the plate, the plate seems more warped than walking, plus it has one hell of a rattle.

 

[Larry J]

Yeh, sounds like the plate. Hope everything works out.
Larry