i had posted in drivetrain when i first started getting some 'clunks' from the 4l80, but didn't get much response. now, last night i put it in park and hear something rattling around underneath the truck. sounds like something metal bouncing around inside the bellhousing. trans temps still fine and shifting is fine except that clunk periodically that is more frequent, and also some slipping when starting off from a light. also some strange whining when decelerating. gotta get to a buddy's shop and check it out, but is it possible the 8.1 has managed to break a flexplate or torque converter? just a blackbear tune and catback, otherwise factory setup (4.10's and 285's if it matters).

if it is one of those two, what are best options for replacement (i do tow with this truck)- not ever gonna build the engine up just want more durable than factory parts to replace with. the 8.1 is rather torquey, especially with some of the TM removed by Justin.

 

if its the flex plate id go with a sfi circleD, id almost bet its the flexplate, ive seen a couple stock ones crack up..

 

I too have seen stock ones cracked. easy enough to check unbolt convertor take a mirror and light and look around the bolt holes to crank.

 

are these flexplates for the 8.1 trucks the same as for other LS motors that i see sold from circle d?

 

noooooo

 

but it is the same as a 2 piece seal neutral balance bbc or sbc 168 tooth

 

ok i had read that somewhere else too, looking for some confirmation. i think i read TCI makes a 168 tooth one for old style 396/427 BBC that is neutral and works. taking it to the shop today so we can take a peek and see what is broken.

 

Check the starter for a loose bendix, that's what mine was. Also there are no aftermarket flex-plates for the 8.1/Allison combination, I realize you have a 4L80E but wanted to warn others reading this. I thought my flex-plate was broken and on Diesel place we talked about it and I ordered a plate only to find it didn't fit and the bolt pattern once measured when I had it all apart was non-standard on the converter. It may be LS but it wasn't BBC.

Vernon

 

Well, no luck- it's the trans for sure. broken hard parts in the case flopping around, and getting louder the more it runs. didn't want to risk something cracking the case ($1000 core on these, boys) so we shut it down. ordered a goodwrench 3 year/100K replacement. for the price i got on it (which wasn't cheap at all) you can't beat the warranty, yet still cheaper than all the performance companies builds- which have little to no warranty. i really don't need all the performance upgrades anyway for my purposes.