I know, some of you are howling ASB, but bear with me.
In the 1860's the American Industry did have the capability, the resources, and the technology to produce something like the WW2 M3 Grease Gun. Things like Caterpillar Tracks and Steam Powered Tractors were around and steam propelled vehicles had been used as far back as the 1790's.
Dr. Gatling did experiment with electrically powered Gatling Guns and Rubber is also not a concern, Tanks used metal tracks for decades and well into WWII and beyond. And Vulcanized Rubber was invented in 1848.
And with the North's superior Industry and Rail system I don't think this is to much of a stretch.
1862.
As the war rages on Lincoln receives an interesting letter from a Major in the reserves.
The letter goes over the problems that Infantrymen suffer in conflict and especially against a dug-in enemy.
The letter then presents a solution. In an old Armory in Washington there are handful of Ironclad steam powered vehicles that were built between 1855-1858 and then forgotten about. Most of the vehicles are in need of repair and would require new parts.
Once repaired however, these 'Landcruisers' would provide an invaluable Infantry Support weapon.
Lincoln's curiosity is roused and he writes to the Major that he will visit the armory and would like to see a demonstration.
Lincoln meets Major Tolliver and is given a tour of the armory and its eighteen Landcruisers. The one working Landcruiser is then started up and rolls out the doors with Lincoln in the cabin.
Lincoln is impressed with Old Abel's cross-country capability and imperviousness to artillery and infantry weapons. He's less impressed with Old Abel's propensity for breaking down and the fact that its top speed is around four miles an hour.
The very next day, Lincoln places the 1st Landcruiser Company on active duty, orders Tolliver to begin recruiting crews for the other Landcruisers and signs an executive order for replacement parts.
Tolliver's new crews work day and night to get their Cruisers working and to know its quirks. As each of the massive Landcruisers were built around different Locomotive Boilers and engines no two are exactly alike and the parts replacement and maintence is a nightmare.
Tolliver also has the problem that his crews are former artillery and cavalrymen, none of which know how to operate a steam engine and all which will require extensive training and cross-training. Nonetheless he attacks the problems facing him head on and by March 1863 Tolliver has gotten the 1st and only Iron Cavalry into working order.
1863.
Gettysburg.
Apart from a handful of skirmishes, the 1st and only Iron Cavalry had seen very little action, but that would soon change. Tolliver's command had by that time been increased to thirty new Landcruisers, but only on paper. In practice he had at best twenty-five Landcruisers that he could call on.
Against Tolliver's wishes the 1st Iron Cavarly had been divided, 13 of his Cruisers were stationed at Gettysburg and 12 with Humphrey's Division at Peach Orchard under Tolliver's second, Captain Albert Patterson.
On the first day of the battle Tolliver's force surged forward through the streets, often ripping away sides of buildings and plowing through trees and fences in an awe-inspiring sight, the Cruisers began to open fire, pouring canister and explosive into the exposed confederates at point blank range and ran over a few confederates that were to slow to get out of the way.
The sight of this demoralized the confederate troops and gave the Union infantry time to rally and retake the town.
Colonel John Buford seeing the Confederate's retreat took the initiative and ordered one of the few Cavalry charges of the war riding into the rear of the fleeing Confederates, killing hundreds (mostly from the weight and speed of running horses) and driving them back into the woods.