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Unresolvable issue with Dodge SRT-10

My mechanic (the dealership unfortunately since it is still under warranty) has not been able to identify the problem…
2005 Dodge SRT-10 Quad Cab
There is a strange noise, or perhaps I should say noises that sound most of the time like a grating/grinding sound. Occassionaly it has less of that mechanical sound, and more of…well, like blowing air over your tongue with a lot of saliva in the way (like a cat purring with a hairball in its mouth??). Anyway, the ONLY constant I have found is that it only happens when I am accelerating (but not everytime I accelerate). Most often (again there have been expections) it happens between 1500 & 2500 RPMs…typically just before the transmission would be inclined to shift to a higher gear - if it does shift into the higher gear, the noise stops. Also, the moment I take my foot off of the gas pedal, the sound stops. About a third of the time, I can feel a slight vibration via my feet when the noise is stronger sounding. On two occasions (this is over a period of approximately 1 year) The sound was extremely harsh, and the truck was shaking.
When I took it in the first time they told me it was the catalytic converter, and replaced it. When that didn’t fix the problem, they decided it must be the other catalytic converter (yes it has two). That didn’t fix the problem either.
Ordinarily, rather than simply have them replace half the parts in the truck I would wait until something completely failed, thus making the culprit obvious. However, I am moving soon… and I don’t want to be driving half way across the country pulling a large trailer and have the drive shaft, or transmission, or whatever - fall out.
Ideas, suggestions, please help.

Is An SRT-10 A Ram 1500 Or To What Other Model Is It Similar ?

It’s the Ram with the Viper’s V-10 engine.

While I know it’s under warranty, you might try to find a mechanic in your area familliar with Vipers and SRT10s, and spend some money to find out what the problem is.

I suspect a universal joint.

The universal joint… is that part of the drive shaft? Forgive my ignorance…

I agree that a u-joint is a possibility.
And, this could possibly be as simple as lubricating the spined shaft that connects the u-joint to the drive shaft.

My experience with bad u-joints is that the noise may diminish when you let off the gas, but it does not go away. It would not go away when the transmission up-shifts either.

I think they should be looking at the motor mounts. The V10 is one of the most unbalanced engines you can get. The motor mounts have to absorb a lot of vibration and have to be tuned to the harmonics of the engine. Since the sound is related to the rpm of the engine and not the vehicle speed, I would be looking at the engine and not the driveline.

Another things to look at would be a leaking exhaust manifold gasket or cracked exhaust manifold or loose baffles in the muffler. Also, consider a cracked flexplate. In fact, I’m liking the flexplate because of the metallic, grating sound.

Again, I’m not all that mechanically inclined, but, wouldn’t they have noticed a crack (or other issue) in the exhaust sytem when replacing the CCs? Especially given that this dealership (really, dealerships in general) LOVE to find “extra” things that are wrong with the vehicle?

Also, I couldn’t think of anything with my limited knowledge, but is there any part of the fuel/air intake system that could cause those kind of systems?
A colleague of mine who is mechanically inclined (but not a mechanic) has been in the truck when it happened, and he also guessed the u-joint, or something along the drive shaft…

There are lots of places for exhaust to leak that are out of sight of when they’re changing CCs (can’t really imagine why they did that, anyway). You now have several possible causes, you should ask the dealer to check each one thoroughly.

Especially given that this dealership (really, dealerships in general) LOVE to find “extra” things that are wrong with the vehicle?

Not when they have to pay for it. After the warrantee is up, that becomes a true statement. They probably jumped on the CC because they could pass off the cost to the manufacturer under the federally mandated 8 year/80k mile warrantee.

The flexplate is like a flywheel for automatic transmissions. It connects the torque converter to the engine. The symptoms of a cracked flexplate similar to a bad u-joint, but are related to the engine rpm where the u-loint is related to the vehicle speed.

So… the flexplate would only be engaged when under load (i.e. accelarating)?

What should I expect the flexplate to run? Is that a relatively low cost repair, or big $$ ?
In otherwords, +/- $500 or is that in the thousands range?

The flexplate is bolted directly to the crankshaft (so engaged at all times), and then directly to the torque converter.

Changing it would require dropping the driveshaft and transmission.

One thing no one mentioned is the transmission. If I’m not mistaken, the quad-cab came with the 4 speed automatic transmission(6 speed manual for the single cab). Have you checked the fluid level/condition lately?

I had the transmission fluid flushed and filled about 9 months ago. Of course, if it’s a mechanical issue that wouldn’t help the trans. much.

The flex plate is always engaged, but under load, it will flex a little. If it had a small crack, then it could cause your symptoms. It shouldn’t cost too much to have it inspected.

But first, I would have the motor mounts inspected and the exhaust system checked for cracks or loose baffles in the muffler. These are easier to get too and to look at.

A defective motor mount would allow the motor to “torque roll” under heavy load and this could allow the exhaust pipes to rub up against something and make the metallic grating noise. This would also allow you to feel the vibration from the motor in your floorboards and pedals.

Thanks all for the insightful suggestions!
I’ll be dropping in for a chat with my mechanic Monday. Hopefully by this time next week I can post the end result.

Just one more thing, the only cracks that I have ever seen in a flexplate were at the mouting bolts to the torque converter, never at the crankshaft. Removal of the engine or transmission should not be necessary to inspect the flexplate where it bolts to the torque converter. There should be a small inspection plate, four small bolts that you take off, then rotate the engine to inspect the bolt area.

It does have to go on the lift and there is a little labor here, that is why I’d inspect the other things first.

Harmonic Balancer and motor mounts checked, flexplate inspected, entire exhaust system inspected, flywheel and u bolts inspected. Still nothing found, noise still there.
Here’s to hoping something doesn’t fall apart in 4 weeks