I like the A3, but they are extreemly prone to tranny issues. The Allison 1545 is an oddball, made from the very popular 545 but with a locking torque converter.
Here is the problem. With the 4th as straight through, the locking torque converter puts additional torque on the clutch pack, but the seals in the piston that hold pressure on the frictions and steels was inferior to begin with as an OEM tranny and most fail early in their life. As they fail to hold, people mash the fuel and MELT the aluminum clutch piston for the fourth/reverse....and it's toast. So that is the bad....and potentially really expensive....but it doesn't have to be.
My project truck is an A3 which had/has that tranny problem. I bought it for $4,500...named it money pit, but it's more of a time thing...loooooong term. I'm making mine a 4x4 and they are extremely popular as a "bobber". Google M35A3 bobber. For just around town and the farm, I don't need the extra axle...it doesn't have posi or limited slip and if one is sliding in mud, the one behind it is too. But air locks and detroits can change that too. Buying for one rear axle is a lot less than 2....same with tires....which you will need.
On the plus side for the SS, it is already a 4x4.
Back to tranny on the A3, since I think you will encounter the problem. The person that sold me my truck bought a used one, went from Detroit to Iowa and back and had a "guarantee"....that was worthless. He installed it and it had the same problem. They had disguised it with new oil and cleaning, but what a disappointment. So I got a very low mile Allison completely apart in a box, with what felt like sandblast medium (friction clutch) stuck to burned oil and melted aluminum drops and a transmission in the truck that is internally the same. I did run it in 1-3 and was really impressed with the Cat.
I have a friend that was Allison and GM certified. He cleaned and checked the parts, which amaxzingly were all there and the gears looked like new. I bought the new master overhaul for the 545 and except for a seal, had all that was needed. The 545 piston and steels and frictions are the same...readily available. More important is that the seals are improved.
After completing a second rebuild for another SS member with the OEM clutch, we found that the direct clutch pack for an 4L80E was interchangable and that there are high performance clutches and frictions that can improve that part of the tranny at very little additional cost. It is thinner, more advanced, and has more surface area from having 2 more plates. I wish I had known about this mod before I put in OEM clutches.
Here is a picture of my tranny rebuilt with a PTO direct mount hydraulic pump, soon to go in.
With so much money in a machine up front it is hard to make significant alterations. You will find A3 at around half of the SS cost, making some investment in addressing the weak link not so bad. There are more items to the A3 like assisted steering and dual circuit brakes (over the A2).
