No help elsewhere, I need help. Horrible noise after installing new flexplate
 

My flexplate recently broke. I have an extended cab truck with 5.3 and a built up 4L65E

I pulled the tranny pulled the flex plate, tapped all the holes, cleaned off the bolt threads etc. Installed new flex plate, which is a B&M from Summit, SFI rated. I used red loctite, and torqued all bolts to spec using the 3 phase sequence.

Tranny went in smoothly. I torqued the converter bolts to spec. bolted everything up and when I started the truck there was a very loud scraping/screeching sound. Doesn't change when it goes in gear/N/R or anything.

couldn't find ANYTHING, so I pulled the tranny out.

The flexplate is warped about 1/8", but it doesn't seem like that would be enough to cause this.

I found some very minor grinding marks on the flexplate teeth. Not marking on the starter, block or anywhere else.


Any idea? I'm stumped.

What bolts did you use? I did a search on here a long time ago and IIRC there were plenty of people who had issues with the B&M flexplate/bolts.
Also IMO, I would not want to use a warped flexplate but hey i'm no expert.

I used the factory bolts that were on my truck. No air tools, just started by hand and a torque wrench.

It's really wierd.


The only possible thing I can think of is when I was tightening up the converte, I threaded in the first bolt by hand untill it was snug. Then I torqued it down, but it pulled the converter to the flexplate about 1/2". The other bolts went in and torqued down fine. Usually I'll snug them all first, then torque to spec. I really doubt it, but maybe it got tightened a little crooked?

would 1/8" out on the flexplate make that much of a difference? I didn't really feel a vibration, just the noise, but then again I didn't drive it, it was still on jackstands.

Sounds like a bolt issue to me too.

If you really did pull the converter out by 1/2" inch then it is no longer properly engaged in the pump. The recommended gap between the converter pads and flexplate is 1/8" to 3/16". At 5/16" you are already really asking for trouble. You should check that gap again, it can be done with drill bits.

I just guesstimated the 1/2", but it did seem like it pulled the converter out more than normal. It was a metal tinging sound but really loud, like the flexplate was hitting something, but I can't find any marks.

I went back out last night and mocked up the flexplate, spun it around to see if it was close to something, and nothing.

It's really weird

The flex plate wa broekn in half, essentially leaving the torque converte "free floating" I've realized. Could I have bent my input shaft? I surely would have noticed a vibration, but there was none. other than the audible noise, it drove perfectly

Here is the new flexplate after taking it out, against the OEM. It is about 2mm wider, not sure if that matters.

Although there are visible markings on the plate, I cannot find any elsewhere on the tranny or engine.


Attachment 727673

Just slightly larger

Attachment 727674

Identical tooth pattern
Attachment 727675

Not hitting start housing or gear

Attachment 727676

Attachment 727677

Slight wear on transmission side of teeth

Attachment 727678

Attachment 727679

transmission side again but another area, untouched

Attachment 727680

engine side

Attachment 727681

little wear (truck never driven, only started on jackstands)

Attachment 727682

Attachment 727683


I put the converter in the tranny, then bolted up the flexplate. i spun it. It wobbled a little bit but that's normal because the converter hangs a little on the input shaft, it's not rigid. But even wobbling it didn't touch anywhere.


I'm starting to lose my mind.

It's possible that your starter stayed engaged and was causing the noise. I initially thought the flexplate might have been installed backwards and was scraping the block or a bolt somewhere.

Keep us updated.

^^^^^^have you checked to make sure the grinding was not in the input shaft/pump/converter area or are you certain it was the flexplate?

I found it!

here is my write up on Performance Trucks.

The flexplate is too big, hitting the starter bearing

http://www.performancetrucks.net/for...2/#post5094466

Listen to the video I posted in my link, you'll know why I was certain it was the flexplate. it had that hollow tinging metal sound, not a flat knocking sound.

Congrats on finding the issue. These little weird things will drive you nuts.

FWIW- Circle D Specialties designed their own custom HD flexplate that fills that void the LS community needed filled. Over kill durability along with pull N play installation sings my song.

I got this plate for $95, I was hoping not to spend more than that, but this just goes to show once again you get what you pay for. I'm disappointed in B&M

I'll look into the Circle D

Is there a different starter I could use? I don't want to pull the tranny again an I don't want to wait for another plate. Someone mentioned starter shims, but I dont know how they would work on this type of starter that bolts straight up from the bottom.

any ideas? I've pulled an reinstalled this thing 3 times in a week. I'm over it.

I has some terrible noise when the starter was engaged on my LS2 with a TCI flexplate. I solved it with two thin stainless steel washers, one on each bolt, place between the starter and block. It moves the starter down and gives more clearance to the flexplate. Yes, a shim would be better, but I didn't have one handy.

If anyone has a part number for LS starter shims, that would be appreciated.

06sierra5.3,

I understand how frustrating you must feel with the issue you experiencing with your vehicle. If I can assist you with anything please let me know.

Jennifer T,
GM Customer Care Service

two stainless 1/16 washers and it's fixed. Thank you everyone for your help

Glad to hear my washer suggestion worked for you too. :)

Now you can install the new camshaft tomorrow. ;)