Help: Loud whining noise/loss of power

[06DuallyMax]

Its not the A/C clutch is it?

Its not the a/c clutch or any gasket leaks. I bought the truck used an havent changed the tranny fuild, i don't know if its getting(it only seems to make the noise over with trans temp over 180 degrees) hot an thinning out making that nosie im thinking about changing it but ive always been told just to leave the transmission alone should i change it or not?

Would either of these actually cause it to lose power? Mine hasnt done it in a while, but I didn't change anything to make it stop.

 

[zhicks2585]

Well mines not losing power

 

[HurtMan]

If it does it under load and seems to go away as you let up on the accelerator. I would look for a pin hole in a intercooler boot or (alluminum pipe). Seen a lot of holes worn in pipe, loose clamps, pin holes in boots.

 

[hdrolling]

I just towed a small trailer from Louisana to eastern Tenn for a week of camping and I had my truck doing the same thing. It only made the noise when the trans temps reached about 200 and I needed to use a little more throttle like getting back on the interstate or passing. After I let off the throttle or the trans colled down it would not make the noise. I thought it sounded like my transmission might be slipping but it sounds like it coming from the engine bay? I'll be following this thread to see if anyone can figure it out or has any more ideas.:thumb:

 

[06DuallyMax]

Well, it definitely seems to be temp related. I pulled yesterday in that extreme heat, and it did it about 8 times on the way home. I did get a video of it doing it this time. It's definitely not a boost leak, as it will go away sometimes even holding steady throttle position. I'm not a diesel expert, but I've had a few boosted cars, and have never known a boost leak to fix itself. Now, on the way home my trans temp got up high enough for the diplay to tell me the trans was hot. I pulled over, let it sit unitl it cooled down, and then went on my way. Is the stock trans cooler in these trucks not up to heavy pulling? Could an additional one be added?

 

[j johnson]

sounds like somthing hydraulic like trans or power steering pump...thats were i would look!! just my 2 cts.

 

[Mike_S]

That sounds like a transmission pump howling to me, either cavitating from the hot fluid, or its been damaged.

On edit, does it seem to correlate with the engine/radiator fan clutch engaging/disengaging?

 

[LBZ]

Sounds like a normal LLY fan to me.....:dontknow:
You lose about 30 to 50hp to the fan when it's fully engaged so that would explain the power drop as well-at least in my mind it does.......

 

[LBZ]

If you are worried about trans temps though, try a Mike L. tranny cooler!:thumb:

 

[BlkMax]

X2

You lose about 30 to 50hp to the fan when it's fully engaged so that would explain the power drop as well-at least in my mind it does.......

I was thinking the same thing. I lose about 200-300 rpm when the fan clutch engages. Which for me is about never, even when towing, our temps just do not get that high....unless I leave the grill and bumper covers on too late into the spring...

Keep in mind you can overheat the transmission and never have the fan clutch engage. The fan clutch on the LB7 at least is tied to engine temp, and the trans can be cooking but not enough heat will get through to the fan clutch to make engagement. The situation that about cooked the trans for me was slow crawling up a mountain road-not going fast enough to get air through the grill and essentially no engine load. All that was pre-MikeL cooler.

 

[06DuallyMax]

That sounds like a transmission pump howling to me, either cavitating from the hot fluid, or its been damaged.

On edit, does it seem to correlate with the engine/radiator fan clutch engaging/disengaging?

I'm pretty sure everytime I hear it, the fan is roaring along with it. If the pump is damaged, would it go back to normal? You can hear in the vid, it returns to normal without me doing anything other than holding the throttle steady. Where can I find this trans cooler y'all are talking about?

 

[Mike_S]

im going to withdraw my initial thought about it being a transmission pump, and go with another fella who believes it to simply be the clutch fan. if you worried about the magnitude of the noise, inspect the fan and clutch, and anything in that general area.

the transmission cooler everyone is talking about will be the small cooler almost directly behind the emblem on the grille.

 

[dude8710]

Check to see if air is leaking between primer head and cp3 with a piece of 1/2" clear tubing. Heard same noise in my lb7 turned out to be a 65 cent oring in primer.

Sent from my C771 using Tapatalk

 

[dirtyLB702]

My lb7 makes that noise ever single day hot or cold I've always wondered what the hell it was it makes it even when I'm not towing and will eventually go away

 

[cafryer]

That is the first thing the gm techs say no matter what the problem is.

 

[Kartmnn]

Did you figure it out?

 

[Harbin_22]

Sounds dumb but it is not the clutch fan kicking on is it. They are loud and rob lots of power when they engage. That and they seldom do come on when empty.

 

[Harbin_22]

I hate when I don't realize how old threads are

 

[06DuallyMax]

That's ok, because it's still doing it. I talked with Mike L about the trans, and he seemed to think it was the converter coming apart and clogging the cooler. I put a new converter in it, along with a shift kit and all was well for a while. Then it just mysteriously came back. I dont know what the hell to do now.