I did this swap on a Mechanical DTA360 with Air brakes..
as others have mentioned the steps.. I think I covered parts of it in my DEV random thread.
the big thing for you is to make sure if your engine is diesgnated as NGD or not.. the NGD engines use a 12 bolt flywheel and the non NGD engines use an 8 bolt flywheel. this is important for the flexplate. from what I have been told by a couple peoplpe on an International forum is that All DT408's use a 12 bolt flywheel, which means a flexplate from a Pre-EGR DT-466E would be the same.
shorter flywheel bolts will be required, how much shorter I dont know since mine is Pre-NGD. I used the opportunit to pull off the flywheel and make sure that the housing-to-block bolts were still tight and inspected the rear main seal to make sure it was dry.
putting the flywheel bolts back in I used grade 8 and torqued with a torque-wrench and just a small Dab of blue LocTite on a couple threads.
is your bus hydraulic brakes with the drum on the back of the AT545? if so you will want to verify the mounting holes are the same on both .. I can measure the mounting hole pattern on my MT643 if needbe.. my old AT545 is gone.
Speedometer - if you obtain a 643 with a Tone ring in it, your speed sensor from the AT545 just fits right into the MT643 and done.. you will need to lengthen the harness.. the harness is a 2 pin WeatherPak connector.
Reverse lights - pressure switch moves right over
Neutral safety - connector moves right over
Yoke - splines are same so moves right over
Cooling Lines - AT545 lines come off the Top of the trans and are #8 JIC (flare).
MT643 has Bosses for #12 ORB (O-Ring-Boss) fittings. I made myself new lines to go to my radiator.. one was going to be too short.
here are the fittings I used so I could use same Hose size or if your lines are long enough you can re-use. these thread into the transmission.
https://www.grainger.com/product/4V...f0cf1e2b964542a1e661efbb6996b91f5214a735fe666
and this is an angle flare to flare that made it easier for me to route my lines from the trans.
https://www.grainger.com/product/4V...f0cf1e2b964542a1e661efbb6996b91f5214a735fe666
Modulator - move from AT545 to MT643
Shifter Cable - I had to modify my shifter cable bracket a little by drilling new holes in it to hold cable so the geometry was right. some people say its a simple move over and bolt up..
Dipstick - Moves right over assuming your 545 is deep pan with dipstick tube going into the side.. and it will still be accurate.
Driveshaft - I used the opportunity to have all of my driveshafts rebuilt, balanced, new U-joints, and Clocked.. eliminated the driveline Vibe I had previous. (yes read about clocking driveshafts).
Torque-Converter-bolts - I was able to access from inside with the doghouse off the bus .. there is a forward facing hole in the flywheel housing to access the 6 converter bolts.. they will have been LocTite'd from the factory if installed to spec. it is not the heat-only loctite so you can get them loose.. I used an extension and tapped on the ratchet as just turning caused the motor to want to turn.. a couple of the bolts fell down into the housing .. I didnt care..
when installing the 643, its converter is studded so when I got the trans close I had used extra long temporary bolts to draw it into alignment .. with a little pressure on the converter.. rotating it from underneath(converter) with a screwdiriver.. one of the studs poked through its hole and made guiding in the trans easy..
a little loctite on each nut and a bit of axle grease to hold the nut in the socket.. and done.. torque with torque wrench.. (and a box end jammed in the inspection hole underneath to keep my engine from turning)..
Horsing the Trans - an AT545 with converter weighs about 350 lbs. an MT643 about 650-700 lbs.. I used a mixture of a Harboer freight trans jack and 10,000 lb ratchet straps to hoist and maneuver the transmissions around.. an engine hoist came in handy for moving them in and out of my pickup truck.. when I did the allison 1000 on my short bus with little wheels I had to put down shiny cardboard and slide the trans under the bus on the ground.. my DEV bus has 11R tires and so I could set the trans on the jack and horse it under the bus.. I did pump up my air suspension to maximum to get the trans underneath.. then I let it back down for working underneath... if you have a helper its much easier. but I have no one to work with me so I must get creative with tools..
the Dog-House. - take this time to make sure that your body and chassis are mated correctly... mine werent.. it let lots of engine heat into my bus.. with my doghouse and trans removed I could fix , insualte, seam-seal, Dynamat, and the like.. the result is much quieter and almost no engine-heat on my feet which gives my Air-Con a chance to cool me in southern USA july / august heat that I travel alot.
I hope i didnt write too much of a book here..
-Christopher
