Growl when in reverse with brake applied...

[bullsnake]

Good evening everyone!
I've got an appointment to have my '96 looked at on Monday, but I was wondering if anyone else had run into this problem. After driving over to pick up some equipment in a little town about 60mi away and back home, I noticed that when I put it in reverse with the break applied I hear a growling noise coming from the transmission area until I let off the brake and everythings good. Runs out fine in drive and reverse works well too. I don't recall it making the noise before, but I have only had the vehicle a few weeks. We had a snowstorm here today and I had to drive it into town and it didn't seem to be as loud in reverse, and ran out fine. Just wondering if this is as bad as I think it's going to be...

[Yetti]

I am not sure as I haven't been under one in years but I would look at the rear trans mount to see if its in tact. the rubber might be torn out and its grounding againest the chassie.

[bullsnake]

Thanks Yetti!
I'll crawl under it this weekend and check it out. I am hoping it's something like this and not a trans. rebuild. Because of it's history with me I'm keepin' the truck no matter what, I just wasn't planning on something major right off the bat. Driving the truck for 2 1/2 hrs straight at sustained speeds of 70mph on the flat and level shouldn't kill this thing, right? I was watching the temp gage the whole time and it was always well within the 180 degree range.

What should a trans rebuild cost if that is the case? I just want to make sure I'm not gettin' hosed...

Thanks!

[phazer42]

I have had issues like this that were brake pad related... replacing the pads and no issues afterwards.....

[bullsnake]

Were your brakes pretty well worn? This truck has had new brakes 1800 mi. ago, but I have always noticed that they squeal a little the last 20-30' when I brake at a stop sign or light.

It's like this:
Put the Hummer in drive-runs like it always had.
Put the truck in reverse-runs like it always had.
Put the truck in reverse WITH the brakes applied, ie. not moving just sitting there stopped with gear selector in reverse and brakes applied=growling noise.

The trans mount seems to make a little sense to me in that if there was one that was toast putting it in reverse may cause the trans to shift under the torque load and come into contact with the frame or body, thus causing the noise. Once the brake is released torque is transferred through the driveline and growling stops.

[Yetti]

one of the other things to look at is the exhaust. if its touching the chassie it will do the same thing. if by chance you can block the drive wheels and have someone look under it while its in reverse you may have a better veiw of the noise or at least a closer area to look at when its off and you can get completely under it. DO NOT get under it with any body parts you can't afford to loose while its running. leave that for trained mechanics...(Thier expendable!)

use a pry bar to lever againest the exhaust pipe mounts and trans mount to see if they are torn. it doesn't take much effort if its torn so don't force anything if it doesn't move.

[bullsnake]

Thanks again for the heads up Yetti! I've got a freind that has a lift and I'm gonna take it over there tomorrow afternoon and see if we can figure anything out. I still have the appt. set for Monday with the dealer, but I'd just hate to send it in there if it was something simple that I could fix.

How common is it for a transmission to grenade on a bone stock '06? Is that a weak point for the vehicle? Are there any other preventative things I should be watching out or doing?

[Yetti]

Never delt with the newer ones. I left the dealer back in `95. I could only assume the later ones are still the 4L80E trans, those used to be bullit proof.

[bullsnake]

Well, I got it figured out. Sorry for the delay in posting-we had a storm roll through here yesterday and I have been swamped at the office.

We got it up on a friends lift Sunday night, and checked the motor and trans mounts and they all seemed to be in great shape. I did notice a fresh scrape on the transmission skid plate/bars and started thinking about how that coulda got there. I had taken the boys wheeling down at one of our farms the weekend before and we were doing some rock crawling over a few exposed areas and I remember tapping the undercarriage on one of the passes. Right where I tapped it was close to where the exhaust was and it left the clearance between it and the transmission insanely tight. We got it down off the lift, and fairly confident at this point that it wasn't the transmission internals at all took it out and drove it for a half hr. and then right back up on the lift. Sure enough warming everything up to operating temps the trans was now touching the skid plate. We took a torch and two pry bars, heated it up and bent it back into shape and viola! no more growl! What a relief that I wasn't gonna have to spring for a transmission!!

Thanks again everyone for all of the suggestions! I don't know as if I would have even crawled underneath it if I hadn't got any responses or ideas from all of you!

[Yetti]

Glad to hear you got it figured out.