Tci 399753
 

I have a 2008 LY6 6.0 is this the right flexplate for a turboo 400 and an older convertor?

Yes, that is the correct flexplate if you want/need an SFI approved flexplate. But you also have options with the factory flexplates as well. If you want to run an older TH350/TH400 converter with any of these flexplates (TCI or stock) you'll need one of the available spacers (GM or aftermarket) to support the rear of converter by the nub on the back. Lots of good info in here:

https://ls1tech.com/forums/automatic...questions.html

And in here:

https://ls1tech.com/forums/automatic...0r4-4l60e.html

Another option is to buy a custom converter built specifically for your application (LS to TH400). This negates the need to run a spacer as the appropriate pilot nub is built into the converter. Mine is a PTC and is application specific. It bolted directly to the TCI flexplate and fits in the pilot hole with no spacers needed.

Hughes performance also makes a flexplate for this application. Let me see if I can find the part number. Eric L

Here it is. HP4004X. IIRC it goes for around $149. Eric L

ok this thread may be way way old but i have a question, just got a built th400 to put behind my already swapped 6.2 ls3 (previously manual in donor car 2010 camaro ss) i already ran an old th350 with stock converter using a flywheel from a gm 6.0 l. And the gm spacer they used with the 4l80 and bolts. I ovaled out the holes to mate it to the old style gm torque converter and ran the car for all summer no problems now i have purchased the tci 399754 as my th400 torque converter (aftermarket) bolt pattern is the larger 11.5 inch and i believe the 399753 is for the smaller bolt pattern converters.. So it seems this tci flywheel has been thickened as to not require the gm spacer and comes with shorter bolts than factory but the spacer is what the converter centering hub adapter fits snugly into so by not using the gm spacer the centering piece that comes with the flywheel doesn't work... And using the spacer with the tci flywheel puts the flywheel teeth way out of line with the starter gear. Must the converter have this centering thing or can the bolts do the same thing??? Im stumped on what should be a simple job and lost the instruction paper i think. Also no where online can i find the instructions!!!!! I explained my info to the tci tech and was told this is the flywheel i need, waiting on another reply as of now...

Thanks for any insight

the 53 has a dual pattern for the converter bolts and the spacer goes between the flexplate and converter.

My new converter has a ring welded to the snout and needs no spacers ;)

Attachment 594226

ok i found my issue.....well one of em haha so my engine was a manual trans prior to my swap and it had the pilot bearing installed preventing me from figuring out the spacer bushing piece with the 399754 TCI flywheel simple mistake haha and for the th350 trans i used first i simply bought a 6.0L flywheel and gm adaptor piece/bolts from the junkyard and ovaled out 3 torque converter holes so it would bolt up and she worked fine. the 6.0 L engine must have a 4l80 trans behind it for it to be the right flywheel for this.

so i now have the flywheel bolted up (399754) the flywheel simply bolts up as normal the torque converter centering ring/bushing slides into the end of the crank freely before or after bolting up flywheel (did not have to hammer it into seat) and the torque converter snout fits snugly into that. the trans and stall torque converter to flywheel are going to mate up perfectly (measured) but when i tested the converter alone to see how far the snout penetrated the bushing it was not fully seated into it thus leaving approx 1/8" or more space where the bushing could walk outwards onto the TC. snout and that creates a situation where it wouldn't be penetrated into the crank enough anymore to keep the TC. perfectly centered.. not good

so is this what you mean by "ring welded to TC.?" i think if i had a ring spacer to put on the converter snout prior to close this 1/8" or more gap it would work great or weld it to the TC. or weld it to the centering Bushing

part numbers for spacer rings??

what ya think? any extra info appreciated thx.