08 June 2023
So it begins! The 2023 "Tech Refresh" for the M113K Crossfire. Each summer, my family heads for the farm in New Mexico for several weeks, but I am left here to go to work, and in my off times, it becomes wall to wall car projects. Two years ago saw the pulling of a perfectly well functioning M112 out of the car, and beginning of putting in a M113K. Last year a 1962 Triumph TR3B got a full engine and mechanical rebuild. This year is back onto the Crossfire. As mentioned in the last post, there are several things I want to accomplish this summer. One will be to replace the stock-type open differential with a much more stout HAG215 differential carrier with a Wavetrac installed, and so that is what was started with.
Here you can see the size comparison between the two, and knowing how small the Crossfire is, you know trouble is already brewing!
This is what a stock differential looks like on the ground, laying in the rear subframe. The subrame is laying on its back, so this is kind of the view you would have if you were looking at your car on a lift
When you lay the HAG215 diff into a Crossfire subframe (and it is indeed R193 specific, not R170!), you see several problems right off the bat
See that forward mounting hole? That's important! The distance between that hole in the diff casing and the centerline of the axle is the same between both types of diffs. That's good news! So, to begin we need the HAG215 to bolt right up on that hole. It is our reference. Everything else needs to move to accommodate. And as you can see above, the diff is larger, so the rear of the subframe will have to move. Time to break out the cutting torch and welder! All the rear mountings of the R193 subframe must be removed so that the mounting portions can be moved aft about 5/8". Did I look to see if this will fit in the car. Yup. It's super tight. Will it fit. Hoping so, but modifications to the car are not ruled out. Hoping a hammer massage is all that is required, but if it needs more cutting and welding, well, we have the technology.
First things first. An R171 rear subframe donated its life after work with a plasma cutter liberated the entire mounting portion for the rear of the differential.
See that extra hole that looks like a third differential bushing might fit? OK, read on.
The HAG215 being used for mock up is from a 2008 Dodge Challenger SRT8. It is the same as found in later W211 E63's and others. This one here is a 3.06 ratio, which was initially chosen to match the 3.07 currently in the car. However, after driving the M113K in a light car for almost two years, the decision has been made to go ahead and swap some guts around with another HAG215 from an E55, which uses a 2.65 ratio. More on that when I get to the point of installing the Wavetrac. In the meantime, the later HAG215 was also chosen to take advantage of the "dogleg" rear mount, which will help prevent wheel hop problems. There are not problems at the moment, but that is probably due to not yet using sticky tires, and not having a LSD. The cutting torch and welder have to be broken out no matter what, so long term success should be baked in now.
Now a similarly shaped but slight smaller hole was cut into the R193 subframe. Hard to orient your eyes at first, but the subframe is standing up, with the rear of it facing up in this picture.
And then checked to see how the new rear plate might sit on it - still a lot of trimming to do, but also spacing it to the rear.
It's going to work, folks! Unfortunately, this part of the project needs to be put on hold. Soon the family will head to New Mexico, and I will be losing my right hand man,
@QuadPrism for a while. I wanted (needed) his help on getting the car prepared now, and the rear subframe project will be picked up later. So, the next big inevitable part of this project, drivetrain removal. Here he is running the engine hoist for me last night:
And empty in here once again
Powder coat on the trans held up wonderfully!
Today everything will be power washed, and put back away.
That's all for now. Will post up more in the days/weeks to come. Thanks for reading!