I just installed a Digitrax DH165LO decoder in a HO scale P2K GP9 and it makes a hum/screech sound when it gets up to about 50% throttle. I didn’t notice this on DC but didn’t really run it much before going to DCC with it. This is a used loco I bought a few months ago and it doesn’t have any cracked gears ( know what that sounds like, still have a few to change). I checked and lubricated all axle bearings, motor bearings and even put a drop into the u-joints (although I don’t think they need it?). It still makes that sound and it is more noticeable with the body shell on. I ran it around the layout at least 6 times and don’t hear any difference. I watched and listened while it ran by me with the body shell off so I could look for anything that might be rubbing, but can’t seem to spot exactly where the sound is coming from. Any suggestions as to what might cause this. It runs very smooth and is quiet at low speeds.
This sounds to me like vibration noises being transmitted to the shell because the decoder is touching it, where previously nothing was touching the shell to transmit the chassis vibrations. Moving the decoder to eliminate contact with the shell may stop the noise.
I would be the RR that you have a bad gear wheel assembly. Pop the covers, remove each wheel/axle assembly and LIGHTLY see if they will twist (one wheel independant of the other). If so, the adhesive has broken loose. Call Walthers and you can get a replacement.
Note this was a MAJOR problem with the GP7/9s and some other P2K locos.
A high-pitched screech is usually the bearings on the motor. A tiny drop of oil like Labelle on each one might be enough. Sometimes the armature can get ‘stuck’ to one side or the other and jam the bearings, if you cna wiggle the shaft back and forth byt he flywheels a tiny amount it should be fine. The Proto drivelines do tend to have too much fore-aft slop like the AThearn drives they cloned, so when runnign on grades, especially downhill, it shifts the whole thing causing a bind and squeal. The cure requires disassembly of the driveline and thrust washers installed in the truck gearboxes in front of and behind the worms. I encountered this while testing locos on various grades to determine the best option for a planned expansion of the layout which never happened, since everything remained effectively flat I never modified any of the drives.
TECHNICAL FACT CLARIFICATION - there is no “adhesive” holding those axles in the gears, it is an interference or “press” fit. The gears that failed were made too small and from a plastic that was too brittle. Age and temperature changes cause them to eventually crack, allowing them to spin. The crack is often so small as to be undectable to the naked eye. I have seen a great number of them last many years then suddenly go bad, again based on age or temerature variation.
I have a moderately large fleet of the effected models, 15 - FA1 & FA2’s, 10 - GP7’s, and 3 - BL2’s. All have had their geared axles replaced with Proto replacement parts. NOT ONE replacement axle has failed.
And in fact I have used Proto axle sets to upgrade my older Athearn units to replace the iron wheels, no problems there either.
The problem the OP describes sound like a motor bearing as Randy suggests or a drive shaft problem, not an axle gear problem.
The axle gear issue manifests itself as a thump thump thump as the locos rolls, every one of my P2K locos that has had a failed axle gear like this has a thump, or a bit of clicking. In one case it would run in oen direction with a thump but actually stall in the opposite dirction. Definitely no high-pitched squeal.
I haven’t had any failures i a long time, because all of my locos are from the known problem date of manufacturer, and I simply replace the gears while I have the loco apart to install a decoder. No replacement has ever failed on mine, either, and that includes many continuous hours of running in club displays. Periodic wheel cleaning and lube has kept the pair of GP7’s I use for my club train in top shape despite the long hours.
I had the same problem with a three unit set of GP30`s a few years ago…I took the trucks apart to clean them and install new axle gears …I reassembled and used very little medium vis. oil …got the loud squealing noise…had to send to Walthers for them to check out …when they came back they had been lubed with white lithium grease.
Thanks for the suggestions guys. I will check the motor bearings although I did oil them and I belive the shaft did move front to back when I played with the flywheels. I know what the cracked axle gear ‘thumpin’ sounds like as I have had most of my P2K’s experience it. This ‘squealing’ as I mentioned only happens at about 40-50% throttle and then all the way to 100%. I was hoping I wouldn’t have to dismanle it down to the motor bearings, but it is what it is. Thanks again.
Lighten up! The problem sounded like it COULD possibly have been an axle problem. The check for that is fast and easy, and something that sure wouldn’t hurt to validate.
The fact (as you state) that the axle is press fit and not “glued” is meaningless to helping out the OP - which was what I was trying to do. Thank you so much for pointing out my erroneous assumption.
At this point, it would seem to me that the first thing to do is remove the decoder and run it DC to see if the sound goes away. I say that because you make the point that it may not have hummed or screeched before you dropped in the decoder. I doubt that the decoder caused the problem, but why not rule it out.
Next, I would look into Randy’s suggestion about the bearings. If you hadn’t said that it was a Proto, I would have thought that it was an Athearn. Hums, screeches, squeals - - - they all emanate from bad, loose or dry bearings.
If bearings aren’t at fault, I would go back and take a look at the axle gears as mobilman44 suggested. True, they usually go thump, thump, thump. But, I have had Proto gears make all kinds of noises when they go bad (cracked). You just can’t rule out anything at this point.
This problem isn’t uncommon with P2K locos, and few forum posts I’ve ever seen correctly diagnose it. Most likely what you’re encountering is an issue with the worm bearings and possibly the axle bearings. P2K had some bad batches of these components, with a composition that will not accept lubrication properly and thus never truly eliminate the noise. One negative side effect is the additional load the bad bearings place on the motor, which does no favors for the life expectancy of your DCC decoder if there’s truly excessive friction in the drive.
Replace the worm bearings with Athearn parts. Note that the worm shaft diameter on newer Athearn mechanisms (ones with the plastic worms) can be slightly smaller than earlier examples, and the bearings on such locos are not direct substitutes for P2K parts. Athearn axle bearings should be a perfect fit for the P2K worm shaft.
You may still hear some noise coming out of the trucks, in which case you can also replace the axle bearings with Athearn’s. I have retrofitted several P2K units with Athearn bearings, and normally the worm bearings turn out to be the source of the squealing noise, but one of them required new axle bearings before it fully quieted down.
I have four P2K locos all purchased in the early 2000’s. One by one they all developed this same problem - high pitch squealing at throttle > 50%. The problem was there in DCC and DC (decoder removed). Only one of the four units devleoped cracked-axel syndrome.
What I’ve learned is that the original worm-gear bearing lubricant used by LL turned green and gummy over the decade. Simply adding more oil did not recitify the problem. I carefully took the entire drive train apart and cleaned with dish soap, using a q-tip to clean inside the brass bearings. Then I re-assembled the drive train and lighly lubricated with Labelle. Voila! Noise gone. Smooth running loco.
That’s good to know. I had a supply of Athean parts lying around so went straight for replacement. I had read on another forum somewhere about a chemical analysis done of the P2K parts, suggesting the bronze was of very poor quality and tended to repel lubrication, so didn’t think of trying to clean the bearings completely first.
One of my older P2K GP’s developed that “high-speed squeal”, and I was able to diagnose that it was indeed the worm shaft bearings.
I managed to quiet it down with some judicial lubricant application, but I never really got completely rid of it. Using Athearn parts never occurred to me at the time.
But it’s been rendered moot; I’ve since swapped out that original chassis for one with sound.