4L80 slight gear whine in P and N

[388 Vega]

Have an 80 that i built about 3000 miles ago with the straight cut gears on the output planet. From day one I have a gear sounding whine when in park or neutral which sounds exactly like the typical 1st gear planetary whine while driving but a much quieter . Noise goes away in R or any fwd gear ( stationary), unit shifts fine, in dash pressure gauge and pressures are normal and steady, never seen over 190 degrees. everything operates normal and quiet.
When I blip the throttle the whine does like what a ford powerstroke turbo sounds like it when you burp the throttle - a lazy spool up and the lazy spooling down in relation to the engine rpm. I don't " think" I have any issue but just curious about the "why"
I know power flow terminates at the fwd clutch housing in P and N but is there any way with parasitic drag on the apply components could the fwd clutch/direct clutch hub/ clutch assy be turning the sun gear shaft which would drive the output gears on the pinions causing the whine? Or thru the fwd clutch hub driving the input shaft and the rear internal gear driving the pinions going that route?

 

[clinebarger]

The OD Carrier/Overrun Housing & Forward Drum will turn a few hundred RPM in Park/Neutral, But no bearings are in play.
Only the Pump/Stator Thrust & the Front Forward Clutch Hub Thrust are seeing a differential.....Both being Plastic from the factory I doubt them to be a source of noise.

Wonder if something is rubbing on the Forward Hub?

 

[388 Vega]

Well I did install the Sonnax roller front hub kit....
If I move the idle up with a calibrated piece of wood on the throttle to about 1200 ish it sounds like the whine will slowly wind down some and pick up in relation to the steady engine rpm but it may be possible the ecu is varying engine rpms slightly.
Since this is an 8.1 swap into an ancient 1986 MH I use a bluetooth adapeter and CarScanner app to build an instrument suite to an old Ipad. I did make a gauge for input and output shaft speeds so when comparing engine rpms to input shaft speeds in raised idle there are some fluctuations in the input shaft speeds - like i said it is a " lazy" sound which makes one want to think it is parasitic drag moving the mainshaft or sun gear tube but not sure if the roller clutch or the sprag will stop that from freewheeling the pinions. The Hydramatic book doesn't describe what happens to the other components outside of the power flow for a particular gear so my dumb azz just tried to connect the dots and follow the purty colors on the cartoons best i can.
I also am using Hy Gard low vis if that makes any difference but i think it is the same viscosity as Dex 3

 

[clinebarger]

The Forward Hub, Mainshaft, Sungear Shaft, & Direct Drum are held stationary....So the bearing on the back of the hub is not in play.

Thinking outside the box & a pure guess.....The Forward Clutch return spring assembly retainer blowing off would result in the retainer rubbing the Hub & it would only happen in Park/Neutral. As would forgetting to install a Thrust Washer on the front side of the Hub.

Surely you checked endplay?

 

[388 Vega]

Yeah both the end plays were checked and front play checked with the tail shaft preloaded =kept the rear tighter than the front. Tightened up the reaction carrier float with 4 tang washer.
If I remember correctly the snap ring for that retainer gets locked into those "humps" on the retainer so you would have a good visual indicator if you screwed the pooch locking that snap ring in unless that retainer is a known issue?
Also wouldn't leaving that thrust washer out show up on the front end play check?
Any known issues using the Sonnax extreme duty fwd hubs that you know of?

 

[MolaKule]

I also am using Hy Gard low vis if that makes any difference but i think it is the same viscosity as Dex 3

Hmm, how would you know if the Hy-Gard Low vis fluid has the same additive chemistry as a Dex/Merc?

 

[388 Vega]

Hmm, how would you know if the Hy-Gard Low vis fluid has the same additive chemistry as a Dex/Merc?

Actually I do not - I do know the viscosity is close. Was just throwing a long shot out there just in case there was a chance that an apply component could be turning another component via parasitic drag could be causing my output planets to rotate. But now being informed that is not possible mechanically....

 

[clinebarger]

Yeah both the end plays were checked and front play checked with the tail shaft preloaded =kept the rear tighter than the front. Tightened up the reaction carrier float with 4 tang washer.
If I remember correctly the snap ring for that retainer gets locked into those "humps" on the retainer so you would have a good visual indicator if you screwed the pooch locking that snap ring in unless that retainer is a known issue?
Also wouldn't leaving that thrust washer out show up on the front end play check?
Any known issues using the Sonnax extreme duty fwd hubs that you know of?

Not a common issue with 4L80/TH400 forward drums, But it can happen. 4L60/E's are known for the Reverse Input Drum return spring snap ring to release at high RPM....So common I tack weld the snap ring on all performance/high RPM builds.

I don't use many aftermarket Forward Hubs as the stock 4L80 piece is more stout than people give it credit (Unlike the TH400 which came with a fairly weak cast hub).
Rarely do I have issues with Sonnax products....Their QC is top notch, But it's "trust but verify" with any aftermarket part OR any new OE part for that matter.

Yes, Omitting the thrust would be caught during front unit endplay checks.