LOUD Transmission drone at 58-62MPH

[jehuty]

New to the forum, sorry if it's on the wrong section. I googled keywords about the issue and came up a thread on this site but no one answered on it.

Issue: Loud tranny drone that's equivalent to having your brains lasered through your ear canal

At speed between and near 58-62 where 60 is the peak.

It's NOT engine related, i've ruled it out.

It's NOT tires.

Source of sound is the tranny because i hear it next to me just behind the dog house and drilling through my right ear.

It's only under load, IE, part throttle or full in that MPH range. Goes away if you let off accelerator within those ranges.

Will also note, sound is not existant when decelerating in those ranges downhill.

Vehicle:

1994 P30 Chevy 454 TBI.
Don't know what type of tranny but gear selector is 1,2,D and D with circle around it.

52k Miles.

[jehuty]

Bird Freak wrote:
Pinion gear in rear end if noise goes away when letting off gas. Sound will travel thru driveshaft.
Been there.

Really? Have you done anything to it?

[jehuty]

It has been a pretty busy day. Have not gotten to check the u-joint or center bearing yet but did take it out to test if shifting between OD and D made a difference. No, it did not

[Bird_Freak]

Pinion gear in rear end if noise goes away when letting off gas. Sound will travel thru driveshaft.
Been there.

[jehuty]

I will be taking the motorhome out today and doing the suggested tips everyone gave. Will let you all know on my findings.

My motorhome is also a Fleetwood flair. 30 feet. I believe I am the 3rd owner and it has made the droning sound since I got it not loaded.

[fyrflie]

I have a very similar sound in my 2001 P32 Fleetwood Flair that almost duplicates your issue.
I have had the noise since the coach was new. Now have 50,000 miles and nothing has changed.
Serviced yearly regardless of mileage. Oil, grease, etc. Tranny also serviced.

I have checked everything that has been mentioned so far with the exception of removing the driveline to check u joints and have found zero issues.
Even replaced the fluid in the rear end. Fluid was clean with no signs of abnormal wear or particles, etc.

I have come to the conclusion that it is simple harmonics caused by extended driveline and possibly poor design. But can’t confirm that.
I do know that with the RV unloaded, the sound is not present. That’s my reason for design considerations.

I will be following this thread so keep us informed as to what you come up with.

[ItsyRV]

duplicate

[ItsyRV]

Assuming you have the GM 4L80 tranny (first gen), there are no known issues you mentioned. That means it may not be the transmission at all or it's a unexpected problem. The closest I could find to any related type issue, but not as you describe is from a filter issue where it's sucking up to the underside causing a vibration when in OD. This is fixed by installing a new filter (and connector) that isn't fatigued from age.

Now, even if it's a internal transmission issue, new parts are widely available as are techs to do the work. Heck, it could be cheaper at times to have a new or remanufactured 2nd gen 4L80E installed. But, odds are it;s not actually the transmission.

[PaulJ2]

I am guessing overdrive gear resonance in the transmission. D is probably straight through input to output. However (D) involves a gear step up and thus some gear noise for some reason.

[jehuty]

hl remington wrote:
eny vibration,could be torque converter going out.

How would be torq converter if it's all RPM and not land speed? Since it occurs between 58-62 mph and not engine output speed?

[jehuty]

ScottG wrote:

jehuty wrote:
I'll take a look at both of them tomorrow. But wouldn't that just be vibration if there is an issue?

Not if you catch a Ujoint before it gets very bad. I've had several of them just do the fiddle thing when they were dry. It was always at a lower speed of around 30~40 MPH. It was worst when up against a cement wall and the sound could bounce off it. I would guestimate it's roughly a 400 to 1Khz constant tone.
I had to take the drive shaft off to feel that they were binding slightly.

Hmm interesting

Also gave me an idea to look up a sine generator online to find what Hertz that sound is and post it here

[jehuty]

All good ideas, will definitely check into it, especially going into different gearing from OD to D. Don't know why I didn't thought of that

Will give a visual inspection underside side and give it a shake down. The drive is a 2 price with the carrier/center bearing.

[NRALIFR]

I had the center driveshaft support bearing on an old truck start making some noise after a clutch replacement once. Man, that thing made some weird noises, and seemed to be influenced by how the driveline was loaded, or not. Took a while to find the trouble.

:):)

[enblethen]

center support
Sounds like the center support.

[ernie1]

How about checking the transmission and/or the motor mounts? If they're bad it could allow the trans to move when accelerating or decelerating.

[hl_remington]

eny vibration,could be torque converter going out.