Rattling noise on gear change.

ChattownXC70 · Post by **ChattownXC70** » 15 Apr 2025, 16:55

Short recap. Bought this car a little over a month ago with a bad transmission. Replaced it and have since been sorting out other issues as I find them now that I can actually drive it. Has about 550 miles on the used junkyard trans and all has been well.

So yesterday I decided to do my last 3-4 quarts of transmission fluid exchange. I’ve done this a good bit now between trying to revive the old trans (and failing haha) and trying to swap all the fluid in my junkyard trans. After I did the fluid swap I backed out of the shop and parked the car and didn’t drive her until today running some errands.

As the car got up to temp, about 10 min into my drive I made my first stop. I had the windows down as it was a pretty nice day. Rolled them up to go in and when I came out I decided to leave them up and run the a/c. That’s when I noticed a pretty loud rattling noise. Sounded like valvetrain noise but deeper if that makes sense.

At first I thought it was engine speed dependent. Seemed like 1800-2200 it would rattle. So I started manually shifting to hold the rpm lower/higher and see if the noise was still there. Sometimes it was but most the time it was gone when I would hold the shift to later.

So I put her back in D and every time the car shifted from 2-3 and 3-4. Sometimes 1-2 and 4-5 if would make that noise. It starts a half second before shifting and lasts until a half second after.

The shifts are fine. Don’t feel any slipping or anything like that.

When I got home I checked the fluid level and it was a little high. I drained 1/2 qt and went for another drive. Still the same behavior and noise. Checked the level and it is dead nuts on the next to top mark so I would assume this is good.

On the way home, I live in the country, I drove with my door open and slowed/sped up to make the gear changes in question to see if I could hear anything and I heard absolutely nothing. I mean, as loud as it is in the car if it’s something drivetrain related I should be able to hear it so I’m pretty baffled. Also, free revving while moving or stationary does not generate the noise.

I am kinda thinking it’s all coincidence that it happened with a fluid swap as I have been doing them about every 200 miles. Either that or the torque converter is crapping out. Which, knowing my luck is probably a more likely scenario. It almost seems like it’s something inside the car. Like in the firewall area. I looked around under the hood and didn’t see anything. I haven’t messed with the rest of the engine in a while. I did do the flame trap/all that jazz last week but have driven it prob 150 miles since then.

Any ideas? Sorry about my short novel. I congratulate any and all who have made it this far.

Post by **Blacklab467** » 15 Apr 2025, 16:59

Any chance it could be something as simple as one of the many heat shields in the firewall/ driveshaft tunnel area making noise at a particular RPM? I've found these can cause problems in the past and mimic sounds like something worse is going on.

ChattownXC70 · Post by **ChattownXC70** » 15 Apr 2025, 18:15

Totally possible and I did not even think about that! I did have to remove the ones under the car above the driveshaft while replacing the trans. I will take a closer look at them Friday. Unfortunately I’m busy the next two days. Thank you for the suggestion and fingers crossed you’re right!

ChattownXC70 · Post by **ChattownXC70** » 18 Apr 2025, 15:38

Well I have poked and prodded around and found nothing to cause the noise. Also, the noise has gone sooooo I have no idea what it was.

Post by **volvolugnut** » 19 Apr 2025, 08:23

Poking and prodding moved the heat shield and stopped the rattle?
volvolugnut

Post by **jonesg** » 20 Apr 2025, 08:07

set up a camera or phone, pop the hood , put it in gear , step on the brakes and touch the gas,
Record, then watch the torque twist of the engine under load.
I had a loose cross engine torque bar that made noise.
Could be worn engine mounts.

ChattownXC70 · Post by **ChattownXC70** » 20 Apr 2025, 12:54

Well the noise can back today lol. I will give setting up my phone a try. Which, I did remove the crossbar between the strut towers while doing the pcv system so that could be it. I will report back with what I find.

ChattownXC70 · Post by **ChattownXC70** » 20 Apr 2025, 12:59

Well I feel somewhat stupid. The timing belt cover was loose. I don’t know how I overlooked that before but just noticed a gap on the front side as I was about to set up my camera. Snapped it back together and I will see how she does in a few hours when I get out after dinner.

ChattownXC70 · Post by **ChattownXC70** » 20 Apr 2025, 18:37

Well on my 25 mile drive all was quiet. I can’t believe I missed that when looking for the cause of the noise. I had the cover off doing the pcv stuff. Not sure why it made the noise when it did and not all the time but I’d say that was for sure it. Everything else I checked seemed tight and secure. If it comes back again I will update here. Thank you all that helped me diagnose it! I really appreciate you all!