I have a 98 4wd blazer that has a loud clunk or pop when shifting from reverse to park. When shifting it causes dash lights to dim. If you slowly move gear selector in between reverse and park it will do it more than once. Seems electrical. To give a little history, it was doing this and seemed like the starter was trying to engage while truck was running. I took the starter off and checked it and the gear was just rattling on the shaft. Nothing held it in place and it certainly did not return to the position it was supposed to. Checked flywheel and converter bolts while I had starter off. Everything looked good. Replaced starter with a new one and there was no rattling at an idle anymore. Yes it rattled almost like an exhaust rattle at idle and now I know it was the starter gear. But now I just have to figure out what is causing the clunk and electrical issue. Almost seems like it might be in the steering column since you can move gear selector back and forth between park and reverse to recreate the problem. Any help would be appreciated.

 

Any ideas?? Just wondering if it might be electrical in the steering column.

 

sounds to me like a motor mount or u joint.

 

Is it possible to get another person to shift trans while you listen outside the Blazer to try to isolate where the noise is coming from?
Just need to be careful and not get run over doing this.

Could be the ignition switch is broken and causing some mis connections within and this is causing the dash lights to dim. Just thinking out loud.

 

It sounds like the starter is kicking out and hitting the flywheel. It is definitely coming from the passenger side of the bell housing around the starter. The starter works great when you start the truck no problems with it when it is supposed to be working. It just seems like it has to be electrical the way you can toggle the gear shift between reverse and park to recreate the sound.

 

To determine if clunk is indeed the starter...I would try to remove the solenoid wire from the starter with the engine running.

Now how to do this:
Prepare a length of 14 or 16 gauge test wire, put a terminal on the end that will go onto the solenoid terminal of the starter. Just strip the other end of this wire bare.
Remove the neg battery cable from battery.
Remove the solenoid wire from starter, then put the test wire with terminal onto the solenoid terminal.
Wrap the bare wire around the Blazer solenoid wire, just enough so that you can easily pull it apart.
Put neg battery cable back on battery.
Start engine
Once engine is running, do whatever is it you can do to make the clunk.
Then pull the solenoid test wire so that the connection is broken.
Then do whatever is it to make the clunk.

If the clunk is still there...then it is not the starter. If no more clunk, then it is the starter engaging when it is not supposed to.....very likely it is the ignition switch sending current to the starter solenoid when the gear shift is wiggled.

Let us know what happens.

Good luck.

 

Thanks Lanny that sounds simple enough. I will definitely try it and see what it does.

 

The noise is the starter. I disconnected the ground from the starter while it was running and no more problems. Now to figure out if it is the switch or a short. Thanks.

 

How did you disconnect the ground to the starter...it is bolted to the engine..???

Anyways good to hear that you isolated it to the starter...almost has to be the ignition switch on the column. Not un common for this to fail.

Let us know.

 

Sorry I meant the solenoid. I used an alligator clip to hold the ground wire on the solenoid and started the blazer. I made sure that it was making the noise still. It was. Then I unhooked the alligator clip holding the ground for the solenoid. Noise went away. And believe me its not had to recreate the noise. So it was definitely the starter making the noise. I feel like it is the ignition switch also. Thanks for your help and I will let you know the outcome. It may be a week before I am able to get it.