Help!! Flexplate to converter fitment issue
 

I have a 2011 GMC sierra 1500. Transmission is a 6L80. Torque converter is a FTI triple disc 3000 stall. I took the stock L9H out of the truck and replacing it with a LSX 376 B-15. This engine has a 8 bolt rear main where the stock engine only had a 6 bolt rear main so I had to buy a flex plate. I ended up going with ATI's P/N 915737. This is an 8 bolt flex plate with a crank adapter.

How crank adaptor works on flexplate: you are supposed to place the crank adaptor over the crank at the rear of engine and then fit the flexplate over the adaptor and bolt them both to the engine.

Problem: tightend the converter bolts up to flexplate and began tightening the bellhousing bolts up to the engine. Before finishing this we attempted to turn the crank to verify that it still rotating. We found that the crank would hang up. It appears as if the converter is being pushed against the pump side of the transmission which is causing it to hang up. ATI swears up and down that this part should fit.

Assuming the converter is seated correctly. Will verify this evening and hopefully take some measurements from the bellhousing face to converter ears. Supposedly supposed to be around 1" and measure from flexplate to back of engine which should be less than 1".

Has anyone dealt with this? Any ideas or potentially other flexplates that others have run with the combinations without any issues?

Thanks for any help!

Not sure if you just typed it wrong, but trans should be fully bolted to engine before checking converter to flex plate clearance. Then tighten converter to flex plate.

When I did my 4l60 to 4l80 swap, my TCI flex plate came with a crank pilot extender. Didn't have to use it as the converter was built to do away with it. The purpose of the pilot extender is to mount on the end of the converter snout and then slide into the end of the crankshaft. Only used if converter snout is not long enough. Snout only slides into crank about 3/16".

Hope this helps.

Shouldnt need an adaptor for a 6l80....

Thanks for the helpful comment bud! Finally able to get the engine back out today. The converter snout was hung in the flexplate. I'm like you I kind of wonder if I even need that adaptor. It seems like it would push the converter further towards the tranny and that's why it may be binding up when bolting everything down. On top of the fact that the adaptor fits so tightly around the converter snout. There can't be more than 1 maybe 2 thoughsanths of wiggle room. It's so tight that if everything isn't lined up just perfectly I could see the snout getting wedged in the adaptor. I also noticed that ATI makes two flexplates 1.) that is labeled for an LSX (this one has the adaptor) and a second that is made for standard GM block but you can get it with the 8 bolt instead of the 6 bolt and the second one doesn't come with an adaptor. I only wonder if that is the one I should have gotten. Going to assess everything tomorrow and go from there.

Thanks again for the helpful comments.

Snout of converter only needs to go into end of crank 3/16" or so when everything is bolted together. When I bought my converter from PTC, they also recommended sanding the paint off the converter snout and applying antiseize to the snout and crankshaft receiving hole. Flexplate does flex hence the name so converter actually moves a little in and out.

Flexplate also allows converter to expand and contract, which is normal for a converter its when they expand and dont contract that it becomes an issue... Alot of times if the converter is tight i will lube the snout with some bearing grease....