Large Scale Central

SD45 vs. SD40-2

i know, a comparison article has already been written up in GR magazine this month, but somebody confiscated my copy before it even got to my house!!! but i dont want just one mans opinon on the matter…i want EVERYONES OPINION as to the real life operational habits of these two engines…i myself do not like the noise nor the gearing of the SD45, so i removed the motors/worm gears from mine and it now is a dummy unit…i do not own a SD40-2 but i have seen one run (outside, of course! ;^)) and tho it is substantially lighter than the SD45, it ran beautifully…the stobe light on the roof was/is a nice touch to if you ask me…but i have heard some bad things about the USAT 3 axel trucks…has something to do with the ‘added’ axel (the 3rd axel basically)??? something about the motor block being the same as the gp’s and f3’s,and the 3rd axel (pivoting if i remember correctly) being an ‘add-on’ and having problems…can anyone elate on this subject???

i wanted to clarify that i AM NOT ‘attacking’ aristo with this post…i said it when they first came on the market, and i’ll say it again, these are the best made diesels on the market today…i just dont like the power bricks…and with that, it all boils down to the gearing…why so low??? totally unneccessary…

I have never had any problem with the pivoting axle on the 40’s. I have had one or two where the retainer was broken, and if you dropped the slider bar off the chassis, the truck would drop down far enough to dis-engage the u-joint.
It is a good way to get 3-axle trucks around Splicer (oops…I mean tight) curves.
I don’t think the blocks are the same----the wheel spacing is different.
Biggest problem to date is the rubber bands.
But, replace those wheels and it’s fine.

thanks dude…but, what do you mean, “slider bar”???

HI Mark.
I love the SD-40-2 no matter who makes it.Highschool days favorite. Hate the rubber tires. they are gone. SD -45 noise, I run sound alot or can’t hear cause its so far away. Love a real puller tho.
I’m hooked on larger locos.

There’s a metal plate, held in with 4 screws, with a curved slot in it, above the pivoting axle. Keeps the pivoter up to the chassis.
There is a lip on the top of the pivoter housing at the truck end that mates with a similar, but inverted lip in the truck top cover. If one of them is broken, when you take the 4 screws out, the pivoter can drop, disengaging the u-joint slipshaft.
Easy enough to put back together, you just have to know what is happening.

well, finally got my december issue of GR!!! :^) all-in-all i thought the article was adequate to the point of describing each loco…but i dont think aristo should be ticked off…nothing bad was said about the SD45…the low gearing and incompatability with other locos (even from aristo) was’nt even brought up…it was stated that the 45 drew more power than the 40, but it also explained that the 45 has 4 motors, while the 40 only has 2…and the second to last sentence in the article, clearly states “Both models have plus and minus points and it is surprising just how DIFFERENT they are.” that being said, i want to know, WHERES THE BEEF???

Read the letter from Aristocraft in the February issue of Garden Railways.

don, you’re kidding right??? aristo sent a letter to GR??? to thank them for the free advertising the got???

Whilst the SD-45 has four motors to the two in the SD40-2. The SD-45 motors are much smaller.
The laws of physics require a certain amount of energy be burnt to develop a given amount of power. The normal Mabuchi type motors in some locos are a little more efficient than others but not by much.
It seems to be just a vague rememberance of the once proud boast by the manufacturer when the SD-45 was being talked up prior to release, that it would “SIP POWER”. What a surprise then to find that it draws just as much if not more than the SD40-2.

I have yet to inspect an SD40-2 so I cannot comment on it.
I have seen at least 5 or 6 SD-45’s and everyone of them has had gearbox problems of one sort or another.
Having rebuilt the trucks in my SD-45 to operate how the designer probably intended them to, the loco is now most efficient. Smooth with no low speed lurch at start up and reasonably low current draw. Personally I don’t think having one gearbox in each truck virtually fixed with the other two gearboxes able to freely rotate about the drive shaft axis is a very good idea. They should all be able to rotate which means softer pads on each gearbox.
The original “rub” fit of the motor terminals to the pick up bus was a good idea but if poor electrical connection was a problem a short length of flexible wire soldered to the motor terminals and the pick up bus would have been a better idea than soldering the terminals directly to the bus. That prevents any “give” and in my opinion will make the drive shaft universals wear out quite quickly. Metal or not.
I have read claims that the SD-45 has vertical and lateral play. Lateral it does, vertical it does not. The gearboxes and therefore the wheels can rotate a bit around the drive shaft axis but they cannot really move up and down.

Otherwise an excellent loco except for the anaemic screws and plastic holes holding the chassis to the body. After about 6 removals and replacements the plastic holes stripped out. Easily fixed.

Best wishes,

Tony Walsham (RCS).

Afraid not. It is not a very pleasant letter. Haven’t you got your February issue yet?

I haven’t seen a rebuttal letter from USAT yet; guess some folks are a little more touchy about constructive criticism than others. You’d think AC would take the feedback and release an even better product. (Personnally, I didn’t read anything really negative in the article, just someone’s observed differences.) After that, I’m suprised that AC hasn’t written this forum to blast the stainless steel track thread…

This post is a bit old but more news keeps coming about the SD40s trucks. I have a couple emails from other SD40 users with driveshaft problems. Shaft is a press fit on the u joint and the wrom gear. The shaft slipped forward into the U joint allowing the drive shaft to come out of the end bushhing and thrash around iside the gear box.
My problems with the SD40 had been completely different. Too small wiring inside to handle the current draw on a derail without melting and also burning the circuit board. No lube on the axles and no directions to this poor newbie to check them for lubrication before running the loco. Ground 5 oblong holes in the axle bushings before I wised up. Replacements? Not unless you buy the whole sideplate assys.
Until about two weeks ago I’d only heard about problems with the articulating axle. Then I lost a gear box to that drive shaft slipping. It was not pretty and I now have an SD40 with one axle not operating. USA has been completely silent to requests for parts information, complaints in the several emails I’ve sent.
I’ve heard of the problems with the SD45 but having seen two late ones run my layout for far longer than my SD40 ever has, consider them far superior. I am keeping the SD40 I have as it was my first G scale loco. Besides who would pay for a limp’in loco! I’m planning to replace it with SD45 or -9.


As nice as the AC SD-45 is the early versions were not without problems.
Each gearbox was supposed to have a softish rubber? padding to allow some independent rotational movement of each gearbox within a truck. However only one set of paddings were installed on the central axle which allowed the hex drive shafts between each gearbox to run out of true and because they were plastic they failed quite regularly. Later versions moved the single lot of padding to one end and replaced the hex drives with metal versions.
I fabricated separate pieces of padding for each gearbox before the plastic hex drives failed and I never had a problem with them.
The metal wiper contacts rusted badly until the plated versions came along.
I had two locos that developed dead shorts within a gearbox that was easily fixed but required disassembly.
The only other problem I had is the body mounting holes wore out from frequent disassembly but that is extremely unlikely to occur with an average loco.

What to do?

Make sure that what you get has the improvements.

Tony Walsham.