I have a 1999 Chevy Suburban with a 5.7L 350 Vortec engine, 2-wheel drive. I had a rebuilt 4L60E transmission put on it and at first it started a little bit rough but pretty normal. It then started making a little bit of a grinding noise, then it got a little bit worse but it would still start and ran fine. One morning, it started but what I think was a metal grinding noise was really bad. I went to come home at the end of the day, and when I went to start it, the grinding was still really bad. Instead of turning over, the grinding sound went away and I heard a spinning sound. I thought it was the distributor shaft spinning but I’m hard of hearing and I’m not very good at localizing sounds so that was just my best guess but I’m positive I heard a spinning sound start as soon as the grinding stopped. (All these sounds are occurring while trying to start the truck by the way.) When I looked under the hood and had my wife try to start it, it sounded like the distributor shaft was just spinning free. I had it towed and pulled the distributor shaft, which looked normal, and reinstalled it with correct timing. The spinning sound was gone but grinding sound was back when I tried to start it again. This engine only has about 30,000 miles on it. Does anyone have any ideas about what type of problem I might be looking at? I would very much appreciate any help. Thank you.
Have you checked the starter?
Starter or flexplate ring problems.
+1 to @missileman If you keep starting the car like this and if the flywheel teeth aren’t shredded now, they soon will be!
I’ll have to guess cracked flexplate . . . very common on GM V8 engines
Take out the starter . . . or take out the stamped steel bellhousing inspection cover
Either way, you’ll be able to get a very good look at the flexplate. Take a powerful flashlight and take a peek. It wouldn’t surprise me in the least bit if the flexplate has broken
If so, this is a very straightforward repair, but not cheap, because the transmission has to come out. At the very least, it has to be moved back several inches, enough room for you to replace the flexplate
To be clear, I’m not saying the ringgear is the problem. I’m suggesting the flexplate itself is the problem. They usually crack next to the bolts, and the crack spreads. When it’s completely broken, the starter spins the ringgear, but the engine doesn’t spin over.
It’ll need to be looked at, but since the problems began after the installation of the new tranny, it’s possible that the engagement problem (whether it’s due to a cracked flexplate or ground-away gears) originate with an improper installation of the tranny. If the tranny isn’t aligned and torqued properly, it can begin to separate from the engine. I’ve seen it once. When it does, the starter engagement gradually gets worse until there’s no longer engagement at all.
If that is the case, it’ll be obvious from below the vehicle. The one I saw had a space so big between the bottom of the bellhousing and the tranny that I probably could have stuck my little finger through it.
My vote would be for the flex plate too. I had that with a transmission change too. It should have been inspected and replaced though with the transmission.