VERY noisy Tranny in neutral... synthetic lube help?

[choppa]

I’ve torn my rebuilt tranny down and see NOTHING out of the obvious that would make my “grrrrrrrrrring” sound with engine running, transmission in neutral, foot off the clutch.
Only happens when warmed up, cold start noise is not there, or so low I can’t hear it.

Once warm it starts and gradually gets worse the warmer it gets.

My guess is (only a guess) that the gear oil “thins” as it gets warm, leaving a thinner “cushion” between the gears.

Only parts moving at this point are the bearings ( front input ball bearing and all roller bearings), the input shaft on the main shaft, and the cluster gear on its shaft.
All those parts look very clean and bright, pit and score free. Excellent finishes on the surfaces bearing ride on.
Those bearings are all new so this should not be happening. The gears and shafts are used, of course.
All bearings are NEW.

I’ve already tried 85/140, straight 140, straight 90 and 75/90 all to no realchanges.
Tried adding a quart of Lucas oil stabilizer. No real change there either.

So before I pull it once again to delve deeper into this problem that’s not going away,
I wanted to try one more (well maybe two more) things:

First I wanted to try a full synthetic 75/140 gear lube. Which is the question I’m about to ask.

Has anyone tried a full synthetic gear lube to quiet a transmission?
And did it work?

I’ve had one suggestion to try an extremely heavy 600 wt oil, to try and quiet it.
He said it helped his situation.

So I’m polling this site to ask about similar experiences and if the heavier, synthetic quieted your tranny or not

[PoW]

Do you have a PTO on it? Perhaps the gasket is too thin and this will make a lot of noise.

PoW

[choppa]

I have NO PTO.

Oh.. it’s not an M37 transmission with synchros or anything.
Its an older, 1941 dodge WC 1/2 ton tranny.
Straight crash box

[just me]

Clutch release bearing bad and not adjusted properly.
Dead flywheel pilot bearing.

[choppa]

All those parts are new.

No. It’s definitely transmission related

[PoW]

Then it must be a bearing preload error, a bad bearing, maybe a snap ring out of place.

Oil viscosity makes very little difference in noise.

PoW

[choppa]

Thanks for the insight on places to look.

I’m probably gonna drop the damn thing again and go investigate.

I should have added this link so y’all can hear the noise I’m referring too.

See below!

https://youtu.be/DclL90LYYfE

[PoW]

Just grabbing here, but the clutch plate only goes one way.

After you pull it, but before you take it apart;

Simulate your in-truck test by holding the output and turning the input on the bench to see if it acts wonky.

If not, set it on a hot plate for a while and try again.

PoW

ps...Synthetic lube will creep out everywhere, and make a real mess in no time at all.

[choppa]

Clutch disk is in correctly.

Trust me, I’ve had this noise for awhile.
I’ve replaced clutch and had tranny out alreadya few times chasing
The simple things like disk in backwards, bad pilot, bad T/O bearing.

That’s all been replaced.

No, I got something inside the transmission doing this.

I’ve been told it’s bad bearings, but they are all brand new and fine upon
Inspection.

[just me]

When I rebuilt my trans I got the bearings from a normal supply source for our trucks.
Two if them were INA cage bearings and very substandard to what was in there. I found correct bearings online and used them you may be dealing with the same issue.
Original bearing was full compliment. Replacement had half the rollers and poor endframes.

[NAM VET]

When I reinstalled my motor/trans, they were all bolted together and very heavy. I have a small leak from the plate which covers my PTO component which has the shaft going forward to my winch. For those who have dropped their trans with engine in the car, using a trans jack, is this something that is extremely difficult, with lining up the input shaft with the crankshaft, or other difficulties? I can drive about 80 miles to my son's home where he has a four post lift if necessary. By the way, I use RedLine MTL in my transmission; a synthetic compatible with the gears and such in the transmission.

I think owning, driving, and working on theses vintage trucks is never really completely done. There is always some little thing that can be made better, or look better. I just finished recovering my seats. Used WeBee canvas, and a new passenger bottom "board" from VPW, which is drilled with the holes and cut to fit, probably some part made long ago. Painted it black and just put my new canvas over the old one, and used my air staple gun to fix it securely. Had to slightly enlarge one of the holes where the circular plates go for the battery box frame pin. Then had a local upholstery shop use hog rings to put my new canvas on the seat backs and the drivers bottom. Looks really good. Now, want to get around to putting new glass in the driver's front swing out windshield.

I really enjoy my 1952 M37, and drive it just about every day. Handy to use as a real "pick-up" for trips to the local dump. Lucky I guess, starts instantly, and I am now quite used to driving it, anticipating braking and merging and such.

Still hot here in UpState SC, but cooler weather coming. Going down to Charleston for a few days tomorrow. Love the seafood there. Picking up my 5 year old grandson and will do some salt water fishing.

All the best, NV

[RMS]

gear oil should not be used in transmissions. 50w synthetic trans oil or atf should be used. gl5 will eat the yellow bits and is too thick to flow through all the little places leaving only grey goo.

[NAM VET]

The RedLine MTL is listed on their site as safe for transmissions, I use their75-90 in the differentials. NV

[W_A_Watson_II]

Lucas Synthetic 50 WT Transmission Oil