Noisy transmission......

[Supermario]

Hey all, looking for some input on proper motor pinion gear placement.
I test ran the motor prior to installing without the case installed. I placed the motor at various depth of mesh and noticed that it was obviously generated more noise with a tight mesh vs a loose fit.
I got it to where I was happy with noise vs gear mesh and not worried about breaking a tooth. But now with the case installed and the motor and tranny in the truck it sounds pretty nasty and I'm considering moving the pinion back a little more but keep in mind I have a 4:1 reduction installed but also plan to haul a fair sized dump trailer and lowboy in the future.
Do you guys just eyeball and listen to the tranny? How far away can I go without damage to gears?

I appreciate any input, thanks everyone.

Mario

[Supermario]

Before I get carried away. This is only my second truck and I never test ran my first, just put it together, not sure what normal is so I made a video. The driveshaft is disconnected so this is stock 540 motor ( Sue didn't like the slower puller motor I had installed initially ) the tranny and 4:1 are under no load.




http://youtu.be/zr5Ym_-3CCk

I also had a driveline issue. The set screw for the u joint at the 4:1 was causing the joint to pull on the output shaft of the 4:1. I need to file the end of the yoke to allow the set screw to fit fully on the milled edge. That's why testing with no driveline and also eliminate axle noise .

[Espeefan]

I always set my pinion mesh so that the pinion gear has just a tiny bit of backlash clearance, when I rock the spur gear back and forth. The old trick of using a piece of paper to set the mesh works out just about right. I like to set the mesh a little tighter then that. However you do it, the important thing is to make sure that the pinion gear is not bottomed out at any point, in the teeth of the spur gear. Rotate the spur gear and check the mesh in more then one place. Sometimes the spur gears aren't perfectly round, and they will have tight spots, when you thought you had the mesh perfect. Find the tightest spot, and set the mesh in that area. Then you'll be good to go. Just double check to make sure the spur gear doesn't wobble a whole bunch, as though it's been seated properly on the shaft, nice and square. Make sure the spur gear shaft isn't bent either. Unlikely, but I've seen it happen on the go-fast RCs.

What kind of 4:1 reducer do you have? I would open it up to make sure the mesh of the gears in there is good. Not much you're going to do to adjust them, as their shafts are ball raced, but you might find the gears are either dry and have no grease, or there could be bits of metal shavings floating around inside the reducer box.

About the only other thing I can think of, that would make noise like that, is maybe your pinion gear's shoulder is rubbing on the spur gear. In other words, the depth of the pinion gear is to shallow on the motor shaft.

[Supermario]

Thanks Guys. Ya, looks or I mean sounds like the motor and tranny are coming out

I know what your saying about gear wobble or gear misalignment Nathan but it all looked fine when I first ran it with an open case. The 4:1 is the new version from PMD which bolts right up to the back of tranny.
I'm going to remove and test without it to eliminate that.
One thing I forgot to mention was the age of the stock motor. I bought this truck used. It had the old 56510 sound unit and old light kit so this thing might have many hours on it and the noise is the motor......

Oooppps, I think I just admitted to installing an old weak motor into my wife's new truck .... Lol
Ok, I'm online buying a new motor RFN.....

Mario

[Espeefan]

Mario, I doubt the motor is the source of the noise. I would guess it's the 4:1 reducer, or something to do with your pinion mesh. Let us know what you find out!

[fhhhstix]

Mario it sounds like the set screw for the pinion is hitting the spur gear. The spur gears in the Tamiya transmissions have side play in them and you may need to move the pinion closer to the motor. Even if the pinion and the spur gear don't have 100% overlap it will be fine. Basically you may see some of the spur gear past the end of the pinion but it is necessary so the set screw doesn't hit the pinion.

Travis

[Supermario]

Originally Posted by fhhhstix

Mario it sounds like the set screw for the pinion is hitting the spur gear. The spur gears in the Tamiya transmissions have side play in them and you may need to move the pinion closer to the motor. Even if the pinion and the spur gear don't have 100% overlap it will be fine. Basically you may see some of the spur gear past the end of the pinion but it is necessary so the set screw doesn't hit the pinion.

Travis

Hey Travis, dont let anyone tell ya you dont know these trucks inside out! I just logged back in to thank Nathan for pointing me in the right direction, i found the problem!! the problem is exactly what you describe.
i opened it up and layed on the bench and just started turning and suddenly noticed this......

the set screw is the culprit !





That would explain the greater noise with tighter backlash when i was testing.

this is the current setting but i will redo now the set screw is clear.



Thanks guys, i really appreciate the help!

oh, and the new truck still deserves a new fresh motor so got one on order

mario

[fhhhstix]

Your welcome Mario, I have heard that sound a few times my self. My best one yet is putting a rear drive axle in backwards in one of mt 6X6's. With the front axle helping out it drove but there was obviously something wrong.


Travis

[TRUCKMAKER]

Its interesting that this came up. When I built mine I tested every thing by moving the gears by hand to see if there was any binding(this was before I installed the 7:1 GRU) It would spin freely and then lock up. I'd try it again and it would be fine. Finely figured out there was enough shaft end play that it would catch the set screw periodically and lock up. As Travis said I simply offset the pinion slightly until it cleared the screw.

[Supermario]

I know, a simple issue. I was trying to figure out how I didn't catch that during testing when I realized I was always looking at the pinion gear from the front and looking at depth and when looking at it sideways I guess never spun by hand enough to see and feel the binding???

Believe me, I feel a little embarrassed but in my defense, it's not something that had me stumped. I knew it didn't sound right and before ripping things apart I contacted my extended family and tapped into the vault of knowledge and experience to find a quick and proper solution
Now , if I would have tore it apart and not figure out the issue, then ask for help.......just bump me back to newbie status please .
And I guess I shouldn't rebuild anymore 777D power shift transmissions at work .....no wait, I can still see those parts no problem

Mario

[1985 kenworth]

yea mario i just logged on and i was going to suggest that about the set screw but travis got you first.....had that problem with poseidon when i put it together ..sounded like a swarm of bees chasing me and i wasn't even outside...i kept thinking the gears were rubbing on the plastic tranny case

[Mikem]

Hi all I had a noise driving me nuts then I searched noisy tranny and behold there is the answer ! Thanks for being there . Mike

[Supermario]

Originally Posted by Mikem

Hi all I had a noise driving me nuts then I searched noisy tranny and behold there is the answer ! Thanks for being there . Mike

Gotta love it when that happens!
I've said it before and I'll say it again.... This forum is a massive vault of knowledge and experience....and we all have the keys to open it up!

Mario