What is the disadvantage of the locking TC in the 1545?
They made 5,600 of the A3's (a small production number) and it was the only model (of the 545) that used the locking feature (1545), making it a rare bird. I believe a committee was responsible for that decision, instead of going to a larger or OD tranny. Alison stopped supporting the 1545 a long time ago and the people that make parts for the torque converter, even repair parts , are no longer available. The input shafts on the locking TC are one of a kind and when worn, won't hold pressure and result in failure, slipping in the TC or the clutch packs, usually the 4th and reverse.
Another issue is the 4th-reverse clutch pack has a seal problem on the pressure piston. They are known to fail early and motor oil complicates a situation. If the tranny has original seals, it is of the age that you can expect failure. The new seals do not have the same problem, making a preliminary rebuild a very good thing.
On the bright side the 545 is extremely sell supported and all the clutches and gears and bearings fit the 1545. The valve body is different, the TC is different and the hydraulic pump is different. You buy the seal kit for the 545 and there are 2-3 additional seals for the locking TC.
Also...found what I believe is the only place that will rebuild the locking TC, making new parts where the old are not available and they can put multiple clutches in the TC like pull tractors use. TC is not a problem then, making the pump one of the most critical parts that I have no replacement for.
Also, one can use the 545 if the stars do not align for you... and get rid of the locking TC feature.
Again, this must have been a committee decision....who puts a locking TC on a relatively low speed vehicle and no OD for higher speed. Oh well.
There are many threads to research, but that is what comes to mind. Oh yea, the 1545 has the ring gear for a tranny mounted PTO and uses the same 6 bolt as the 5 tons, it just turns a little slower. Unlike a 5 ton, it has to be direct mount since there is no room for a driveshaft and remote mount pump due to transfer case placement in a deuce.
Guys with a Cat 3116 in an LMTV may have some additional info for alternative tranny's but most LMTV use electronic tranny's, I think. If it looks like the GM 400....it's very close and some parts may even interchange.