I have two quite new Walters H0 SP GP20 (http://www.walthers.com/exec/productinfo/920-31490) and got today at ebay two very old Life Like GP18 Susi-Q expected to arrive next week. Both have low nose.
I wonder if I can put the old Like Like GP18 Susi-Q shells on the quite modern Walthers SP GP20 drives. That would save me the hassel of getting 20 years old drives up and running.
Has that shell swap already been done?
Reinhard,
You are looking to put older “Tan” box GP18 shells (they have those movable sunshades?) on new-ish GP20 chassis, correct?
Yes, I have done this. It is not a straight swap, but its an easy alteration.
The GP18 has movable radiator louvers that stick into the shell cavity and will keep the shell from sliding over the weight of the GP20. Those movable louvers lasted only that one run If you look at the weight of the GP18, it has sections notched out of the weight whereas the GP20 won’t.
I remove the grills, which press fit into the louver assembly, take apart the louver assembly, and CA the part where the grills pop into back into the shell’s slot (you’ll see). Then cover the hole with thin styrene from the inside. (You can leave it as a see thru grill but the light will probably shine through it.)
With your skills, I’m sure you’ll figure it out.
I don’t recall if the light bezel/numberboard’s need adjustment, but its an easy fix.
Edit: You’ll need to shave the depth of the louver/grill “holder” so it doesn’t stick into the cavity, or find another way of securing the grills to the shell.
And you’ll want to fill in the gap in the pilot with styrene or permanently mount the GP18s footboard’s, since that will be the only way the shell will be solidly secured (The Walthers production of the GP20s used screws near the fuel tank).
Thanks a lot. You made my day 
Check for the edit of my previous post.
Thanks for the update. I had one of the old ones many years ago and remember the moveable grill. Should be no problem to fix that deviation. The front will get a snow plow anyhow, I intend to modify the shells to the year 2000+ version.
The old NYS&W GP18s arrived today. The shell swap was as easy as you wrote. The louvers are removed for a first quick check. I have to think about a permanent solution. The old truck frames got a black coat and fit into the new trucks too. The tanks swapped fine too. Thanks a lot.
Glad to hear its working out. I forgot about swapping the tank.
IIRC, the grills are a bit smaller than the holes left after removing the louver assemblies, so its a bit tricky to just cement them into the holes. I reuse the rectangular piece of plastic that originally held the grills in place, but have to shave it down severely in order to make it narrow enough to clear the GP20 weight. I suppose using styrene strips around the inside of the holes will make them small enough to hold the grills.
There are probably other solutions for mounting the grills. Good luck.
I glued a very thin sheet of styrene behind the hole, a thicker into the hole, painted it black and finalle glued the thin louvers on top from the outside.
The status so far. Some details and serious weathering is next
Later that day at the early evening
Excellent work! Love the ditch lights and other details. Great weathering too.
I’m not a big fan of the LifeLike moveable sunshades that were standard on those first run GP18s, which is another difference from the GP20 runs. Removing the channel leaves a noticeable trench in the roof, which must be filled. After filling, I’ve put on small rain gutters like the Reading does with its diesels to hide my repairs, but perhaps a strict SusyQ GP model wouldn’t have those.
I have an update of the louver mounting method.
My seggestion was to use a thin sheet of styrene inside, a thicker one in the hole and glue the louver on top from the outside.
That is fine except at one engine was the inside styrene not totally flat and got bend from the chasis when I put the shell on the drive. The three layer construct needed to be redone.
But I used this time Kapton tape inside to hold the thicker styrene in the hole until the glue had set. That ensure no interference with the drive inside the shell.
It looks like the Kapton tape does not interfere with the usual styrene glue and can be simply removed when the glue has set.
ps. You may omit the inner styrene and the Kapton tape all together if your styrene fits perfect into the hole and needs no support until the glue sets.