I just finished my new 396 stroker and have less-than 100 miles on it. I don't have it apart yet, but it appears the flexplate bolts to the crank hub are loose. I can feel slack between the flexplate and crank hub when I try to rotate the flexplate and torque converter with my hands. The torque converter is tight on the flexplate.

I used new ARP 12 point flexplate bolts (PN 200-2902) and a new TCI internally balanced SFI approved flexplate (PN 399174). The bolts were torqued to 70 ft lbs w/ ARP moly lube under the heads and thread locker as I recall. So, I'm not sure just what went wrong here? I know the torque was correct on the flexplate bolts. Hopefully, I can tell what went wrong when I get it apart today, or tomorrow. Also, the Vigilante 3200 stall converter is nearly new and worked perfectly on the old engine. So I'm sure it isn't out-of-balance and causing the problem.

Has anyone else had this same problem with an LT (the flexplate bolts loose) with only a few miles? I also plan to call TCI today to see what they think.

 

I talked with a TCI tech person today and now I think I know exactly what went wrong. However, I still don't have everything apart yet.

When I explained the loose flexplate bolt problem to TCI, the first question was, "is the flexplate powder coated?" My answer, "it is." The tech person then told me, "I need to sand the powder coat off where the bolts torque to the plate."

Here are my thoughts on this subject now. First, there "were not" any installation instructions with the TCI flexplate. Again, nothing enclosed about removing the powder coating where the six crank bolts install. Additionally, if TCI is aware the powder coating can be a torque problem, why are they coating that area of the flexplate? Also, I think the tech person chose his wording very carefully to not admit they had caused the problem. Rather he said, "here is what you need to do to fix the problem." Basically, no responsibility with the problem admitted. And, I didn't confront him on the issue. However, I have a friend who knows everyone at TCI, so I'll let him handle it.

And now that I think about it, I can see how the powder coating on the flexplate could provide a false torque indication, then crumble and cause the bolts to become loose.

Anyone else have this problem, or any comments?

 

Educate me as to the valve of powder coating a flexplate.

 

Never heard of a powder coated flexplate, but FWIW flexplate bolts should be installed with a thread locker (Loctite, etc.). Did you use a thread locker?

Rich

 

Thread locker was used; although the apparent problem was the powder coating (not sure how many mills thick) provided a false torque indication and/or crushed the under bolt head, therefore causing incorrect, or no torque load on the bolts.

When I described the loose bolt problem, the TCI tech support person focused directly on the powder coating issue. Also, when you look in the Jeg's catalog at the TCI flexplates is states, "Powder-coated gun-metal grey. SFI 29.1 approved."

 

Man, they should have provided instructions in the form of a warning label, in that case. Very shoddy, IMHO. I would not have thought about removing the powdercoating, and I am pretty damn smart

Rich

 

I never thought about removing the powder coating either, and there wasn't any instructions enclosed telling to remove it. Furthermore, why in the heck are they powder coating that area of the plate (where the bolts go) if they know it is causing a torque problem????

I bought the TCI flexplate for two basic reasons; 1. The new engine is internally balanced and the factory plate is external, 2. The TCI is .030 thicker and SFI approved (I thought it would be stronger). The powder coating was incidental.

I'm pulling the transmission tomorrow and will get a good look at everything, then I'll post the results. I have new bolts and “another new” flexplate if needed, as the holes in the old plate may be messed-up from the loose bolts.

Also, I have two bracket races for points left this season and hope to have everything sorted-out and be at the track this Saturday.

 

The holes will be wallowed out.
Ask me how I know. OTOH, don't.

The crank hub bolt holes should have 1/32 clearance but the pin hole should fit very close to the pin. I peened my hole smaller to get all the play out of my ATI flexplate.

If the plate can't rock when loose you increase your chance of it never loosening.

Dean

 

Your not the only one with that problem.

http://ls1tech.com/forums/showthread.php?t=359076

http://ls1tech.com/forums/showthread...&highlight=tci

 

That's pretty bad. They should mask the area where the bolts go before they powdercoat the flexplate.

 

I took it apart today and the "cause" of the loose bolts "was" the powder coating on the flexplate!

The powder-coating was "really thick" on both on the hub side and where the bolts torque. The coating was delaminating and indented which caused the loss of torque. Also, the flexplate was destroyed due to the bolt holes being elongated. TCI said they would make it good, I just have to send the flexplate to them.

The car is back together and ready to T&T at the track this Friday. I still haven't been down the track with my new 396 stroker yet.

http://www.cardomain.com/ride/2189634

 

yep....built a 383 earlier this year...same flexplate.

when my engine builder and myself put the motor in, we installed the flexplate, used thread locker and torque it down and even verified it again. sure enough 2000 miles later, they backed off

they really should include some sort of warning or instructions

 

So how can you tell when the flexplate is loose?? I have the same flexplate installed before I was aware of the powdercoating problem but what would the loose flexplate cause? What symptoms did you guys' cars have?

 

If you have a cam with any lope, it sounds like the lockup clutch is trying to beat itself out of the converter shell.
Sounds real nasty.

Dean