I did some quality work on my wife's 93 Jimmy yesterday and today. I got the 4WD working. There's another issue, however; a knocking noise coming from somewhere under the truck.

I started by listening to the valve covers with my stethoscope and didn't hear the knocking through there. I listened to various other parts of the engine and didn't hear it. It sounded like it was coming from somewhere under the truck so I got down underneath. After consulting with a friend I removed the inspection cover from the bottom of the bellhousing and checked the flex plate and torque converter bolts. The bolts were tight (35 ft-lbs) and there were no cracks in the flex plate. My friend started the truck and I listened to it with a piece of heater hose. The noise definitely sounded like it was coming from the torque converter.

The noise is present at idle and goes away under load over about 800RPM. What could have happened to the torque converter to cause that problem? I just put a new transmission in it back in April. I don't remember whether the rebuilder used the original converter or if it was a new one. Does this problem indicate imminent failure or can my wife drive the truck for a while? Is it time to start my new career as a faith-healing mechanic?

 

Hmmm odd sound & odd sounds usually = $ I know it's tough to isolate a sound but are you sure it's the torque converter? The torque converter is at the back of the engine but so is the distributor. The distributor being at the far back & almost under the firewall might make the gear sound of it sound like it's coming from under the vehicle. Our GM's have (as I've heard) an inherent issue with distributor shaft bearing & or gears going on them. They can have really odd sounds, intermittent sounds, non symmetrical with valve train because the noise issue is floating.

 

I'm sure it's the torque converter. I listened to everything on the top of the engine with my automotive stethoscope. The noise was definitely louder when I was under the truck. It was loudest when I had the inspection cover off the torque converter. I even took a piece of heater hose to listen to the various areas under the truck and it was loudest at the torque converter.

 

Today a buddy and I pulled the transmission back and unbolted the torque converter from the flex plate and discovered cracks in the flex plate on the inside of the crankshaft bolts. We got a new flex plate and we'll install it on Tuesday or Wednesday. I'm awaiting a set of bellhousing dowel pins. The truck only has one dowel pin currently. The idiots I took it to last summer pulled the transmission out and only put one dowel pin and four of the bellhousing bolts back in.

I should hopefully have my wife back on the road by Wednesday.

 

It took until midnight last night but I got the Jimmy back on the road. I love these trucks. I can just keep fixing them and they just keep running.

Inspired by something I read here on the Blazer Forum I found a handy way to replace the upper bellhousing bolts that weren't previously installed. Using two long extensions I was able to get the bolts in. I laid on my back with my feet pointing toward the front of the truck and was able to get the bolts in relatively easily. There was no need to jack the body off the frame or cut holes in the floor pan or anything else.

Now the wife can drive her Jimmy and I get my Blazer back.