think I cracked the flywheel again

When I bought my m1009 it had a cracked flywheel and was making the typical rubbing sound when in reverse. I did not know this at the time I bought it as it was the first time in a long time owning an automatic, so all of my flexplate and torque converter knowledge have come from the last year of owning the Blazer.

Fast forward almost one year and I've found that the truck is making the same faint rubbing sound it had made last winter. I'm certain that the flywheel I purchased was for a 6.2 diesel, I'm certain that I did not bolt it up backwards, but I'm also certain that something is not right if I've managed to crack it again already. Is it possible that the th400 is on its way out and busting the flexplates is a symptom?

From what I've read, cracking the flexplates is not uncommon but it isn't considered a user consumable item like brake pads either. Has anyone else bumped into this issue? Searching through the forum didn't turn up much on repeat offender type stuff with regards to the bum flywheel.

I wonder if 1 or more of the 3 bolts connecting to the torque conv. could have come loose and started rubbing....just a shot in the dark, but it is an easier fix

have you changed all your motor and transmission mounts ? on my old 3/4 burban having broken motor mounts led to a cracked fly wheel.

4bogginchevys said:

I wonder if 1 or more of the 3 bolts connecting to the torque conv. could have come loose and started rubbing....just a shot in the dark, but it is an easier fix

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He will surely have a problem if he's dealing with a 3 bolt converter/flexplate as a 6.2 diesel/T400 has a 6 bolt converter/flexplate.

11Echo said:

He will surely have a problem if he's dealing with a 3 bolt converter/flexplate as a 6.2 diesel/T400 has a 6 bolt converter/flexplate.

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missed that one didn't I, lol. I've taken a ton out, 350/400, but never have I seen 6 bolts....learn somethin' new everyday

I would definately check the converter bolts. I have had them come loose and make a similar noise. Blue lock tite helps.
Brent

did you use a torque wrench to torque the flywheel down .did you check the pilot hole in the crank for wear? were the dowel pins both there and sticking out the proper amount and are the dowel pin holes in the case in good shape ? there are several things that will cause a flywheel to crack maybe the converter wasnt pulled up all the way to the flywheel before the coverter bolts were tightened just to give you a few things to look for but these are just the easy ones to see other things might include to much crank end play poor conections on ground or positive battery cables causing the starter to kick back or not fully engage the stater which could crack it to check those first

I used red loc-tite, with a torque wrench. The pilot hole looked fine though I did not mic it or anything as the transmission was only slid back about 3" so I could get the job done. The dowels were there and the flexplate was not worn out in any fashion for its bolt holes. I did rotate through a complete revolution to confirm that everything was snugged up tight and proper after I finished. I cannot say that I recall everything in perfect clarity, but I didn't find anything out of place when I buttoned it up.

My concern is that the transmission side of the TC may be loose and that was what caused the original issue. Stranger still, the noise has gone away completely the last two days. This weekend I will be out of town, but I plan to get the truck up on the lift and at least confirm for certain as to whether or not the flywheel is rubbing the lower bellhousing cover. I'm also going to run the flywheel around and check the torque converter bolts to make sure one hasn't worked loose somehow. Thank you all for your input and I will let you know what I find. If I see no evidence of rubbing, I'm going to assume that my issue is simply being too paranoid.

tm america said:

.did you check the pilot hole in the crank for wear?

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Dont think autos utilized the pilot hole, just manual trannys.

All the other ideas sound good though.

If you contune to have the problem. There is a brace. It looks like a ring with the bolt circle in it. You will need the longer crank bolts used in the manual trannies. It bolts on and clamps the flexplate to the crank. It was used on the 6.2 and 292 L6 gas powered short school buses. A transmission parts dealer can get it for you. It will cure flexplate cracking issues.

4x4 Forever said:

Dont think autos utilized the pilot hole, just manual trannys.

All the other ideas sound good though.

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I thought he was referring to the recess in the crank (where the pilot bushing would go) that the nub on the end of the torque converter lines up with. I agree though, with both spinning at the speed there should be no issue with slight derivations in the arrangement.

Ken, thanks for the heads up on the ring clamp. If it turns out I need to swap out the flywheel, I will pick one of these up and some manual transmission bolts.