I noticed a few days ago when I came to a stop and held the truck in place with the brake that I would feel and hear a strange knocking sound. Then I heard it slightly while accelerating. I also found that if when stopped at a light that it will stop if I shift into neutral,and shift back in to gear. any ideas. maybe a flex plate?

 

Sounds a lot like it.

 

Is it a knock, knock, knocking;

or is it a single clunk?

Mine clunks, and it is something to do with the rear axle / spring mounts / axle wrap / etc. that I haven't bothered to nail down yet.

JP.

 

When the flex plate broke on my old '93, I coulda swore that I had a bad rod bearing. Sounded horrible.

 

How do I check if it is the flex plate. What happens if I just keep driving it for a while.

 

Pull it off and look.

I drove mine for several weeks like that with no problem but I'm sure that that isn't a great idea.

 

If you're lucky, about the time you decide: "Uh Oh! That boy's fixing to crawl out from under here!", and pull over to the side of the road, pulling the transmission presents with big gouges where the broken webs of the flexplate have dug into the engine/trans adapter plate . . . .



You pretty-much have to pull the trans to see the flexplate in it's entirety, . . . .








Try using a big heavy piece of iron bar, crowbar, really big screwdriver, . . . whatever, and placing one end to your ear, press the other end against different locations of the engine. The block specifically. If it's the flexplate, you should be able to trace the knock to the bellhousing/rear lower block area.
As rigid as the crankshaft is, it tends to transmit the knock to other areas that could lead one to think it's a bad rod bearing for example.

Hope this helps.

 

Oh yeah, about 4 months after I replaced the broken flex plate, The front of the T/C broke off and left me on the side of the road 400 miles from my tool box. I suspect all the flexing from a broken flexplate isn't good for T/Cs. Better off to fix it sooner than later I would think.

 

I dunno on this one. It would seem to me that, with the factory torque converter and stock engine, you wouldn't have enough power to rip out the flex plate. But....

Before mine crashed, I did hear funny sounds on accelerating. I'd call them a pinging sort of sound, like a gasser pre-detonating. Then, accelerating uphill from a red light, there was a terrible grinding noise and the engine revved without power to the rear end.

So we had a wonderful week in downtown Magee, Mississippi, but the folks there did get it back up as soon as the part (second-gen flexplate) arrived.

I'm with BC847; find something big and try to trace it before you go to the big bother of separating the engine and trans to look at it. BUT - if you want to, and have the time and equipment, this would be the perfect time to replace the stock flexplate with the upgraded second-gen one. Then you'll know one way or the other.

Regards, DBF

 

I have two engines that are both out of 1990 trucks with engine build dates of late 1989. The flexplates on both of these engines are different than the ones pictured for 1993. Is this early design without the holes better than the 1993 models or is it also subject to the same cracking failures?

 

I have not had time to take of inspection cover to check flexplate,but I have noticed that if I come to a stop I can get it to quit making noise if I turn the steering wheel so that the power steering pump is putting a load on the engine. I also just put on a new belt tensioner that has needed replaced for a long time could this have worn the bearings on anything else that the belt runs,causing the noise I am hearing. It is not so much a knock, more like a dull rumble.