4L80e Flexplate

Well the truck's been down for awhile due to a cracked flexplate. I pulled the trans out today and found that three ears (bolt holes) on the bell housing were already broke. The flexplate has a circular crack all the way around the crank bolts. I'm guessing the cracked flexplate cause the ears on the bell housing to break?? When I did the 4L80e swap, the guy I bought the trans from had to find another flexplate becuase it went with the motor when he sold it. Well the one he sent me was a little rusty looking but it did come with all the bolts and the spacer. I had a slight vibration in the drivetrain at highway speeds when I first got my truck running (maybe due to the rusty flexplate?) I'm sure the virbration caused my problems but I'm not exactly sure what was causing the vibration. I'm looking into ordering the TCI LS1 to 4L80e flexplate (part# 399754).. Does anyone know if this flexplate retains the factory spacer? Or is anyone using any different flexplates with the 4L80e? Any comments on where vibration might be coming from is appreciated. Thanks

TCI 399754 TCI Heavy Duty Flexplates

From looking at it and its description, I would guess it doesn't need a spacer. Call TCI and ask!

As for the vibration, just make sure to use new bolts and bolt it on in a star pattern--hand tightening first. Tighten to 110 ft lbs. Then back off bolt one turn. Retighten to 35 ft lbs and then turn bolt a additional 140 degrees.

when i bought my TCI flex plate ( 4l60e) yeah i know its different but just letting you know i got a spacer with it

I got the truck back together today but there's still a vibration in it. I'm thinking it could be from the converter, the drive shaft (slip yoke), or the modified crossmember. It occurs bad when traveling highway speeds of around 70 and faster. Any ideas? I'm not sure what to do at this point because I'm almost positive it's the vibration that caused the flywheel to crack in the first place.

Since your truck is dropped, is the pinion angle set correctly????

Whats the common adjustment??? (I am asking the dropped suspension guys :) ) -3?

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Originally Posted by txarkitekt

Since your truck is dropped, is the pinion angle set correctly????

Whats the common adjustment??? (I am asking the dropped suspension guys :) ) -3?

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Yeah, the pinion angle is good. I think it has something to do with one of the components of the 4L80e swap. Before the swap, everything was fine.. But after I put the 4L80e in it started to have this vibration which caused the flexplate to crack.


It seems like there's only so many things that it could be.. During the swap I changed the converter, trans, slip yoke, and crossmember. It seems that other people use a TH400 slip yoke with the stock driveshaft with no problems so I don't think that would cause the vibration. I'm starting to think the 80e converter is bad because it also has a little bit of lag when you select a gear before it actually engages. Could this be a symptom of a bad converter along with the vibration?




Thanks

Check and see if the vibration is there in park and neutral. If it is then it is probably converter, if not then it is something in the driveshaft and back.

Chris

FIXED!!!

It was the slip yoke that was causing the problem. Denny's driveshaft sent me the wrong slip yoke (too short)! At highway speeds when I let off the gas the yoke would try to come out causing a bad vibration. Also the driveshaft was a little out of balance from when I had to burn the factory U-joint out with a torch. I got a new slip yoke and the driveshaft balanced today and it runs A LOT smoother.