Changing transmission fluid

BuyAmericanIron · August 15, 2015

Not sure regarding the 6L80e in your truck, but will certainly be a very tight fit. Not a huge job to loosen/lower the Y pipe. On my truck with the 8L90e (I think that is correct) GM smashed the left side pipe where it travels under the transmission pan to a thickness of about one inch and tucked it very close to the pan. I am 98% certain the pan will not come off without lowering the Y pipe on this truck. The pipe is basically the same height as the transmission crossmember when looking underneath the truck. On the 8 speed there is no dipstick or dipstick tube. Like the Corvette has been for a few years, there is a very specific process to fill the transmission after service.

Pictured in a post above, someone welded a nut to the trans pan and then sealed with a bolt. OK for a drain, but I would not like the drain plug hanging an inch below the surface of the pan. That could be easily damaged by road debris or driving off road and lead to an unexpected tow. An aftermarket pan will probably contain a drain plug that sits flush with the pan but they are costly.

tnchevy · August 15, 2015

I always changed my trans fluid on my 2002 every 30k miles till I got rid of it with 125k miles on it and it always shifted great. I didn't change my diffs and transfer case till the truck had 100k miles (8 years old) and ran into a problem. After the fluid changes my front diff started leaking at both axle seals and continued to leak till I got rid of the truck 4 years later. The dirty diff fluid was what keept the leaky seals plugged but when I dropped the old and put in the new (not synthetic) is when I started slinging gear oil. I guess I am saying that you either need to change all the fluids early and often or don't touch them at all. My work trucks get treated badly and we never change any fluids besides oil and drive them till they start falling apart which is about 5 years and 150k miles. I think with this truck I am not going to change anything but oil and coolant when required and just monitor the rest of the fluid levels.

BuyAmericanIron · August 15, 2015

From post #10, yes the transmission pan gasket is reusable. It is a steel gasket with rubber molded on each side. No need to replace it unless it is damaged. Not sure about your differential on a 14. On the 15 trucks, the gasket is the same material as the transmission. Just wipe it off and reuse. Great design by GM. They got this one right!