LC+ RS-3 Gear Change

Are the gear ratios the same, old vs. new? 

The worm gears on your old motors may not be an exact match in terms of diameter and pitch for the worm wheels in the new power trucks.  Likewise, if the worm and worm wheel are made out of similar materials that's a bad combo.  (Steel worm and bronze worm wheel is best.)  Considering what you have invested, why not go all the way and order new motors as well?

Yes it's a shame you have to resort to this.  When I started reading reviews and seeing photos on the Forum, the cost-cutting was evident.  For the benefit of others,  you might post the part numbers for everything you've ordered.  If someone else locates one at a deep discount, and is willing to risk that parts are still available, having the parts numbers would help a lot!

Replacing the gears is NOT a drop-in replacement. 

I have no beef with Lionel, I like the LC+ line, and this one, enough to buy the parts to upgrade.  Lionel are not the only ones using plastic gears - they work great on many models, and are standard on most HO.  Plus, the LC+ line was originally aimed at more casual hobbyists, many of whom run w/o ballasting track, etc. and I have ballasted track.  At least once a piece of ballast got into the gears of this one, which is probably why the tooth broke. 

Some basic information.  It's hard to find out when and which models had the plastic gears and which had/have metal gears.  The PRR RS-3 (6-38816) that I bought was bought in 2016.  Later ones MAY have had metal gears, but I would bet there was only one production run of the PRR and w/ plastic gears, since the engine was not shown in later catalogs, AND the original "Center Gear Shaft w/ Helical Gear" from the PRR model is shown as unavailable in the PRR version parts list.  

To tell metal from plastic I scratched the face of the gear w/ an Exacto, and the black oxide scrapes off of the metal ones exposing brass or bronze.  The current "Center shaft with helical gear" assembly is supposed to fit, so just replacing the center shaft might be all that is needed.  I went the whole way because I want the loco to run for a long time.  I even bought another PRR RS-3 (also w/ broken gear) for parts from a guy on the Forum, so I can keep my original one running.  

6802171510 is the new shaft w/ a metal drive gear (they have all had bronze helical gears I think).

To do the full plastic > metal gear upgrade:  

2 new power trucks                                       6802171510

2 new center gear shaft w/ helical gear      6802171078

4 Traction Tires                                              6801365206  

2 bearing / plastic / gear shaft                      6002328080  these were included on the gear shaft that I received

The total was a little over $100.

Thanks Mike.  Somehow the combination of parts you have are not compatible.  Are the traction tires rubbing on the ornamental brake shoes?  Based on your description, the Peabody loco performs the way I would expect it to.

Lionel contracts with various factories in China for each production run.  Sadly, unlike in the past, parts from one run of locos are not guaranteed to be compatible with those from a later run.

IF there is a complete selection of mechanical parts available from the same recent, metal-geared diesel, then I would buy all of them and do a complete swap.  My $.02.

New discovery:  (I have edited my earlier posts to include this finding)

In my effort to figure out why the RS-3 is SO loud, and seems to be struggling- I went to re-install a new center shaft w/ metal gears in the original power truck.   The new center shaft would not work, BECAUSE the new gears on the power trucks are a different ratio- the replacement power truck contains a gear set set with much larger intermediary gears.  Resulting in a final drive ratio much lower = higher motor RPMs = higher noise levels = lower top speed and gearing.

So- the upgrade is NOT a drop in replacement.  You have to

- replace the power trucks AND the center shaft as one, and

- replace BOTH power trucks, since the gear ratios will be different on the new setup vs. the original.

It still seems to be "jerky" though so I have not yet figured that out.  I will run it, hoping the gears wear in and get smoother.

Some great detective work Mike!!  If you still have it apart, I would love to know the actual gear ratios, old and new.  You can determine this by putting a pencil mark on one wheel and turning the flywheel on top of the motor by hand.  Count how many turns of the flywheel it takes for one revolution of the marked wheel.

This WON'T hurt the motor, and it is also a good way to check for burrs or binding in the gear train.  Thanks so much for sharing what you've already done.  I just wish I knew WHEN (i.e., what catalog) Lionel switched to the metal gears with improved slow speed.