Well.......I finally got the new 385 running right but now I have another issue. I finally got the thing out on the highway for the first time since I have about 250 miles on the motor. I had alittle fun accelerating and everything seemed fine while driving until I got off and slowed down to a stop and I could hear kind of knock but it is more like a knocking rattle. It wasn't too bad in drive but sound way worse in park...it freaking loud, my nieghbor heard it in his house. My wife said it sounds like a bolt came out and is flying around in the motor. I looked around and found the trans was loose in a couple of spots, tightened them down and it didn't help. I looked at the converter and it was tight but then I saw a large crack in the flex plate between crank and one of the holes in the flex plate. Its like a 1/2 in or so and is clear through.


I figure this is really bad but is the description on the sound consistent with a flex plate crack?

Also when I get a new flex plate do I have to have the hole engine balanced again or can the company I bought the kit from use the number they wrote on all my parts to balance it for me? It is externally balanced.

Could the trans coming loose cause the problem? Could it have been a bad plate to begin with that couldn't handle the power? It was not sfi approved.

Should I expect them to warrenty the part with only 250 miles on it?

 

the sound is consistent with a cracked flexplate, warranty i would say yes.flexplate is balanced from factory, you shouldnt have to rebalance the engine at all, get an sfi approved. worth the money.when mine cracked it sounded like the engine was coming apart.jimmy

 

I thought when you buy a balanced assembly they balance the flex plate also on a externally balanced rotating assembly...no?

 

It depends whether they balanced it the "smart" way or the "silly" way. The smart way is to leave the flexplate balanced to the factory 400 spec so that it's interchangeable with any other identically balanced flywheel off the shelf. The silly way is to modify the balance of the flexplate with the rest of the assembly, making it a unique piece and requiring you to disassemble the entire engine and rebalance it just to replace the flexplate.

 

i had this same problem the flexplate was cracked bacause the bolts were to long in the transmission and it didnt sit flush with the engine so everything was crooked and cracked my flexplate around every bolt hole

 

Cool, I talked to the company and they said the flex plate is balanced to the factory spec so I bought a sfi approved flex plate to try to prevent this from happening again.

Thanks