That's a nice adapter. I was going to make one as well until a friend found one for $145 Canadian. I figured it was money well spent. I did make a #2 to Ford 5R110 that's working great for my Detroit swap.When I found out what they wanted for one, I made one by hand. I started with a 3/16 thick stainless steel disc 20" diameter. (material I had left from another project) I laid out the 24 3/8 bolt holes and drilled them. Next I roughed out the center hole by drilling many 1/4" holes next to each other in a circle and cutting between them with a saber saw. I mounted the disc (now a ring) on the #2 housing on the engine and doweled it in place. (now the fun part) I mounted a lathe tool bit to the flex plate along with a long handle to turn the crankshaft. After several hours of turning the crankshaft and slowly inching the tool bit out into the ring (with lots of measuring I got the center hole in the ring to the correct size. Once this was all done I pressed thread inserts (PEMS) into the inner set of bolt holes. I had to make a centering piece to locate the torque converter and once again lots of careful measuring, turning and bolt hole drilling. I haven't had a chance to run the assembly yet, but everything should be concentric within a few thousandths.
Lathe tool bit is to the left of the larger "C" clamp
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Before the thread insert were pressed in. Note the 3 small dowel pin holes.
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Does the Allison 1000 have a rear mount? If it does there's nothing wrong with adding a crossmember for support. I know when I bought my engine it just had the 2 rear housing mount with the Allison 545.There was a guy on Ebay trying to sell cracked ones from multi-fuel military trucks for $250 and I knew I could do it myself for little more than my time and I wanted the thin style, so I went for it.
Do you have an opinion about mounting an Allison 1000 off the back without a rear mount. I'm set up with one front mount and the two on the flywheel housing? That is all the Allison 643 had.
There's plenty of flex on the rear trans mount, so I would not worry about frame flex. As long as it's the proper rubber trans mounts, you'll be fine.It does have a rear mount, but I worry about adding bending stresses due to frame flex.
I've heard of suspending the rear of a trans with springs on a class 8 truck. (just to take some of the weight, but nothing rigid)