Intermountain cab forward - different runs

[ATSF_Ron]

Does anyone know how to tell the difference between the different runs of these?  I have one with part #79002 and one with #79004.  Road numbers 4275 and 4287, respectively.  Both run exceptionally well, but the 4275 has a bit of a "growl" to it.  Nothing objectionable, but a noticeable difference from the 4287.  Also the 4275 needs a LOT more throttle (in DC) to get it going compared with 4287.  My question is, does it matter which version I have when selecting a decoder?  I would think not, as they both have the NMRA 10 pin socket.  I plan on using straight DCC, no sound.  Yes, I know.  For shame!  I'm just not that wowed with N scale sound.  I mean, my BLI steamers are fun to run with sound, but half the time I just turn them WAY down or off entirely.  The whistle and bell features are nice, but the chuff can get annoying after a while.

I'm fairly new to DCC.  I bought an MRC Prodigy in 2016, I think.  About half my locos are still DC, and are likely to stay that way.  Some of it is cost and some is convertibility.  I have several MDC 2-8-0s and 2-6-0s.  Great runners but a PITA to convert to DCC, or so I've read.  I also have several brass steamers and several Atlas, Kato, and Lifelike/Walthers diesels that are great runners but not "DCC ready."  Anyway, I'm rambling.  Any feedback on the Cab Forwards is appreciated, thanks!

Ron

[Mike Madonna]

Hey Ron,
Regarding which "run" you may have, take a look at the "label" on the end of the box. If it's white, it is the first run. If it's a light blue label, it is the second run. The made a third run, but I'm not sure of that label since I never owned one. Also, the first run ACs have a "golden white" LED. The second run has what I call a "bright white/slightly bluish" LED. IMHO, the first run LED is more accurate for the model. As an aside, I had the second run (blue label) 4280. It never ran as well as the first run locos. I even sent it back to IM for repairs. Upon it's return, it was slightly better, but not on par with the first runs. I have the 79001 4275 loco. I installed a LokSound Select Micro (older version) sound decoder and a 11 x 15 mm speaker/enclosure. Does it sound great with the "Cab Forward" sound file? You betcha! Now, when I turn off the sound, that loco is almost stone silent. I have 4 more from the first run and they ALL run smooth, silent and will crawl. That said, they are geared a bit low. For my operating scheme, this is not an issue.
As for a "motor only" decoder, I personally would recommend the ESU LokPilot 5 Micro #59820 decoder. ESU is known for their superior motor control. I have a Kato GS (4449) that has an Econami in it and another one (4453) that has Loksound (older Select Micro, NOT a V5). The running characteristics of the 4453 is much better than the 4449. This may not be a "fair" comparison since the 4449 has an Econami and NOT a Tsunami 2. FWIW, ESU has THE correct sound file for the GS since Matt Herman (when he was with ESU) recorded the 4449.... so it was a no brainer for me 

[ATSF_Ron]

Thanks Mike. That’s a lot of good info! Apparently, these are both first run as they are both white labels on the box ends. And they have the golden LEDs. I’m extremely happy with how they both run! Even on DC I can make them crawl practically at one tie per second. I don’t have all of my modules built yet, so I can’t test the pulling power on this. But I hear they are excellent pullers.

[carlso]

Ron,

Let m throw my $0.02 worth in. First, I must be carful because I am not an IM fan, but I'll be nice.

I had one of their original run 4-8-8-2 many years ago that lasted about 2 years and then poof with no help from them. That's an entirely different rant.

I acquired a locals "leaving the hobby" stash and one item is, Wala, a IM Cab Forward. I too had  no idea what run this loco came out of so I called IM and was told it is from the "last run" we did and there will probably never be any more runs in the future. Disgruntled employee ? ? As info, the label has #79006S with road # 4276 on it. Yes, it has factory (?) installed ESU LS and speaker. It runs well and sounds good. However, it will not pull hot butter up any incline, 15 cars about the most. Not proto at all. I have thought about not keeping it, just can't make up my mind.

I would ditto Mike's comment about the ESU LP #59820. I have used several and the locos perform flawlessly.

I know, I probably muddied up the water.

[Mike Madonna]

FWIW, at this past year's N Scale Weekend (Altoona) there was an IM AC running on the Free-Mo-N layout. It was pulling 36 MTL cars (plus caboose). I was a bit impressed. On another note, the IM ACs are NOT "heavy weights". They ARE detailed to the max, almost to the point of being "fragile". On the other hand, my 1984 Key/Nakamura ACs all weigh between 7.5-8 oz. Now, they WILL pull 

[ATSF_Ron]

Carl, thanks for the info. Hopefully the two I have will last more than a couple years! 😳

Mike, I haven’t been able to test pulling power on these yet. Years ago I also had a Key/Nakamura version. Still kicking myself for selling it. 🙄🤦🏻‍♂️