Can a tranny knock like an engine on start-up?
 

87 Silverado 350/700R4. Every morning when I go to work something is knocking like an engine rod knock. Thats exactly what it sounds like and then after about 5 seconds its gone and doesn't return till next morning on first start-up. I thought ok drive it till it craters then drop in a new crate engine. But it wont die. 2 years and counting. If it was a rod bearing it would of packed it in long ago? I'm now starting to think its the tranny?. Its really hard to hear where its coming from, but its loud. I have a vibration as well that has always been there since I bought it. I believe its the torque converter so Im thinking about getting the tranny rebuilt and see if thats it. They did have problems with vibrations due to torque converters back in the 80's..

Re: Can a tranny knock like an engine on start-up?
 

Cracked flex plate?

Re: Can a tranny knock like an engine on start-up?
 

sounds like the flex plate if its not the motor

Re: Can a tranny knock like an engine on start-up?
 

Take the inspection cover off the transmission and remove the torque convert bolts. That will help isolate the transmission from the engine noise. It will also allow a better view of the flexplate to check for stress fractures.

Re: Can a tranny knock like an engine on start-up?
 

Only once a day first thing in the morning? If it was a flex plate wouldn't it do it on every start-up? I know I should roll under and take the cover off. Cold makes it worse.

Re: Can a tranny knock like an engine on start-up?
 

Could be detonation.
Easy to check, just pull the vac hose off the vac pot on the distributor and plug the hose (a golf tee works).
Less messy too!

Re: Can a tranny knock like an engine on start-up?
 

Had a noise like that start up a few weeks after installing a new crate motor. Turned out to be the power steering pump.

Re: Can a tranny knock like an engine on start-up?
 

Unbolt torque and slide it back then fire it up the next mourning.

Re: Can a tranny knock like an engine on start-up?
 

I've experienced the same issue but with a different vehicle. Its a 95 bronco. the oil pressure started reading high then i noticed the knock at start up. started out loud then quieted down after 4-6 knocks. and yes it was only in the morning(after all the oil drained down back to the pan....) I changed spark plugs and oil. went with a 10w-40 instead of 10w-30. the knock stop instantly, but a few days later oil pressure started reading high again... still no knock. only thing i could think of is the oil pump could be taking a little to long to get the oil to top and down. reason i say that is switching to a heavier oil helped instantly, keep in the upper block longer.

Re: Can a tranny knock like an engine on start-up?
 

Piston slap. After they warm up and expand, it goes away till the next day.