JoshC04

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!

Area 51 Racing

iTrader: (5)

You're going to call me crazy but on my 4L80e/Yank PT triple disk I literally had to smack on it pretty hard with a rubber mallet to get it fully seated. I tried to install it, thinking it was fully seated and had the same problem as you, binding up. I've never ran into this problem before with my other 4L80 in my Z71, previous 60s, or even my Fords but it was definitely not fully seated. Give it a shot but don't get too carried away with the whooping but it just sounds like it isn't seated completely.

RyanR

JoshC04

Lol sometimes things take a little extra persuasion. I don't feel that that's the issue in this case though. I previously out this converter in with the stock L9H and stock flexplate and the converter clicked 3 times and she was in. I ran it like that for 6 months or so and never had any issues. Sense then I've bought a LSX engine with a 8 bolt rear on it so I had the change the flexplate. That's the only thing that has changed so it has to have something to do with that stupid flexplate. I can only figure that they sent me the wrong one. It shouldn't be this friggin difficult. I want a stock like flexplate dimensionally but with 8 holes instead of 6 lol. SMH.... I hope I can get something figured out soon though. Thanks for the advice! I'll keep that one in my tool box

JordanH

iTrader: (16)

Just run the stock lsa flexplate, part# 12636325... They're like $50 and pretty beefy. Never seen or heard of one failing on some pretty high hp combos.

lbz34

iTrader: (3)

I **** out a stock flex plate on my ls1 car, 1200hp on the glide might do that. I run thicker ones now.

JordanH

iTrader: (16)

It was a stock lsa 8 bolt flexplate? I wouldn't dare use a regular ls1 or any other factory Ls flexplate on any decent hp/tq build..... But the Cts-V/lsa one is pretty damn thick! It's what a few big name engine builders use and recommends on all their lsa crankshaft builds.

JoshC04

So you guys believe that I can just order a LSA flexplate (no need for the stupid crank adaptor) bolt up the flexplate and be ready to rock and roll? heck maybe the local GM dealership will have one in stock but I'm not gonna hold my breath.

Thanks guys!!

JoshC04

I found that the ATI flexplate will not work with my 6L80 and FTI converter. The bolts that hold the flexplate to the crank end up hitting the converter and keeping the flexplate to converter from seating all the way. Leaves about a 1/8" gap. I tried bolts with a smaller profile head and everything still wont seat properly. I'll post pictures later today after I run by the shop.

FYI: do not run ATI flexplate on LS engine, 6L80, and FTI converter. It will not work. You would actually have to take material out of the converter shell to make it work.

I just ordered a LSA flexplate which is substantially cheaper 80$ vs ATI's nearly 400$. So hopefully that will work.

JordanH

iTrader: (16)

Yupp, just google 12636325 and getcha a ctsv/lsa flexplate, and you'll be good to go!

JoshC04

Just an update for the thread. Thanks for all of the help! I took JordanH's advice and picked up a LSA flexplate for around 50 dollars at a local GM dealership. Problem solved and trucks out of the shop.