6.2 flexplate chatter
I recently installed a new Powerbuilt/Reviva 6.2L w/Banks turbo in my 1990 GMC Suburban. This has increased a problem which has occasionally occurred in the past which is a chatter/ping sound under acceleration. This started with my previous custom built engine which was installed in 2001. It now occurs regularly under even light acceleration. The chatter disappears immediately at any road speed when the throttle is lifted or the transmission is shifted into neutral.
It appeared that the starter Bendix drive was periodically contacting the flexplate ring gear. Reasoning that the drive was not fully retracting, a new starter was installed and the chatter became near constant under even the gentlest acceleration. Close investigation of the starter/flexplate area with my mechanic revealed that the flexplate deviates from true run-out by as much as 3/16" during powered running rotation. A second new flexplate was installed and it was close to 1/4" out of true. The first flexplate has the greatest deviation in the area of the balance weight, the second is 90 degrees off that! I am pretty sure that the first flexplate is the one the original 6.2 w/factory option Banks turbo was built with in late 1989
Despite a lot of web searching I have been unable to find much discussion of this type of problem, causes or solutions nor any source of extra stiff/trued flexplates. Lots of stiffened/thicker and balanced plates available for high powered gas engines but none for our 6.2/6.5.
Has anyone else run into this after boosting the HP & Torque on these engines? Any ideas for causes solutions? Thanks for your help.
1990 GMC R2500 SLE Suburban 6.2L TD. Powerbuilt/Reviva engine w/DSG Phazer timing gears, Peninsular 124GPM water Pump & Dual Thermostats, Banks Sidewinder Turbo, TH400 AT w/GearVendors OD, 4.10 14 bolt diff, Amsoil Dual Bypass filter w/Shell Rotella synthetic. Factory 2003 GMC HD alloy wheels with LT265/75R16 BFG RuggedTrail tires.