Two unidentifiable noises coming from transmission. - Hello Gents, I've done quite a bit of searching and haven't found any solid results so I'm looking for help. A buddy of ...

Hello Gents,

I've done quite a bit of searching and haven't found any solid results so I'm looking for help.

A buddy of mine recently aquired a 2001 Silverado 2500 H.D. It's a great truck that runs strong and is a pleasure to drive/ride in. It is a Crew Cab 4x4 with a 6.0L and a 4L80-E transmission. It doesn't have any performance issues or any apparent problems (it runs and drives great), but it does make two odd noises that we are 90% sure comes from the transmission.

The first is a very high pitch whinning or whistling sound (almost like a tea pot whistle) when the truck is put in drive. We first noticed it while at a stop next to a concrete wall (in a drive-through). It is usually very faint almost inaudible and almost too high pitch to hear. While we were sitting there he put the truck into park and the noise immediately stopped, as soon as he put the truck back into drive without moving the noise started again. it stayed constant while letting off the brake and letting the truck slowly roll forward and didn't change pitch or tone, but it is too quite to hear while driving at any speed that requires pressing the gas. We got it to his home and the sound seemed to be gone but very quitely came back after putting the truck in park and back in drive a few times and letting it roll forward in drive (under idle) a foot or two. I leaned down under the side and front of the truck and it seemed centered around the transmission. Now I know it's not a belt as it's way too high pitch and quiet, it sounds almost like an electric component whine, though I wouldn't rule out a small bearing going bad.

The second sound comes while accelerating but only in first gear. When taking off you can hear another whine/squeak sound, almost like a belt slipping but has a deeper tone to it (sounds more like tires burning out than a belt slipping). It too is very quiet (you can't hear it with the windows up) and I'm 99% confident it is not an engine belt (he replaced the tensioner and belt recently). I've done some searching around and found this transmission (I believe) has straight cut gears in first which could be the sound we're hearing. I'm willing to believe this because straight cut gears make a lot of noise when the faces slap together, but the only reason I question it is because it doesn't sound like typical gear noises (I've been an industrial machinery mechanic for almost a decade).

Any help you guys can provide would be very much appreciated! Is there any problem here or are these typical noises from this rig? Thanks in advance!

I think your first noise might be your torque converter. When your vehicle is in park, the TC doesn't really do any work and it has no load. The front pump is driven by the torque converter which is nothing but a direct connection with the two notches on the hub section at the back of the converter. So no real "moving or slipping " parts there. When you put it in gear, the converter is splined to the input shaft is held by the forward clutch and now it has to work somewhat. I hope this helps.

Phill,
If you want to be taken seriously on a site that is blatantly a "Chevrolet Silverado and GMC Sierra Truck Specific Site", that advertises itself as "The only site focused on Silverado/Sierra trucks exclusively", and whose header states "Chevrolet Silverado's and GMC Sierra's... PERIOD."
you should have chosen a different user name and avatar, or be prepared for some serious ribbing or worse...

Nice that you've got a friend with a Silverado. And nice of Gordon to give you a serious response.

Welcome... I think

Let's photoshop a bowtie on his avatar.....

Nice, you guys are cute . I'm glad we can all be adults here! I'm sure you read the entire post and completely understand that my question is about his 2500 so I won't knock your reading abilities or attention span! I'm ready for anything you can throw at me in the form of ribbing or whatever, I had no delusions that I wouldn't get razzed at some point or another. Give me your worst as long as you can handle the return heat!

Thanks Gordon for the serious answer, I appreciate it!

We ALL know the Ford jokes. Lets look at it as USA IRON and go from there.

I like this guy...