It was the flex plate - now, how bad is it?

451 Views 13 Replies 7 Participants Last post by DieselPro, 13 d ago

truckr65

Discussion Starter · 14 d ago

Previous thread: Can anyone help me identify this CATASTROPIC engine noise?

As @DieselPro mentioned quickly after I made the post - it was the flex plate making that awful engine noise.

I started by pulling the torque converter cover, which the flex plate had made a deep groove on the inside of.

After sliding under I immediately saw that at least 4 of the 6 bolts on the flex plate obviously wasn't torqued to spec (66ftlbs), because I could turn them by hand. A couple of them had almost worked their way halfway out already.

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So, how did the flex plate bolts undo themselves? I don't know.

A couple of years ago the old starter went bad, so I swapped it out with this ...

... sold by a local importer. They didn't advertise it as original GM, but not as a Chinese knockoff either.

This is what it looks like today, attached to the block (I have never shimmed this starter).

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The starter support bracket has always been secured to the block. I suspect that the starter, not being authentic GM or shimmed, worked it's way wrong into the flex plate. The damage visible on the flex plate teeth is only on the side towards the starter gears.

The Recommended Course of Action
The way I see it, I have a few options.

The most expensive one being swapping both the flex plate and the starter.

What would you guys do? Is it possible to just tighten the flex plate bolts back to specs and possibly shim the starter?

I would greatly appreciate your two cents!

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DieselPro

· #8 · 13 d ago

Never use shims under a 6.5 starter. If the starter requires shims get one that doesn't. Use the red Loctite and lots of it. Make sure the replacement flex plate matches the old one . > teeth and counter weight. Thanks for the recognition, sometime I feel like Rodney Dangerfield here. "I get no respect".

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DieselPro

· #10 · 13 d ago

SnowDrift said:
Are you serious about the red Loctite?

There is very little difference in the removal torque to remove the Loctite especially on good bolts you can get a hold of. If it was some delicate mechanism or long threaded small screws that would be another story. In this case where the bolts are a sloppy fit in the overly large holes in the plate I feel more comfortable with slopping the Loctite around the hole just to fill in the gap as it sets up. If your worried about removing a red Loctited bolt just don't put as much on the threaded portion.

Tech Tip of the month >>> One of the torque converter bolt holes in the flexplate is OVAL shaped......Start & tighten that one first! This hole is narrow. What it does > The other holes are slightly bigger and it allows you install one bolt at a time and tighten it up till you move on to the next one. Keeps you from having to install all the bolts loose and then tighten.

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DieselPro

· #11 · 13 d ago (Edited)

The oval hole in the plate is referred to as a "Indexing hole"... Not all plates have this feature.. Transmission guy showed it to me... I guess it allows the factory to torque all of them down in one rotation.

Also a neat tip maybe on your truck > You can take one bolt out of the hood hinge and swing the hood straight up. Re-insert the bolt in the new hole that shows up and the hood stays straight up while you work on the engine. Great Chevy Idea nobody knows about. Makes getting to those rear bolts a whole lot easier.

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DieselPro

· #14 · 13 d ago (Edited)

If you look at one you will see an extra hole in the hinge Just take one bolt out of each side and flip the hood straight up. Re-install the bolt into the new hole. What's great > one person can do it and the hood stays on the vehicle. Guess we need a new thread on just that.
99-2014 >>

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