Cutting into the crane’s chassis to gain 70 millimeters of differential height marks a significant step in the lowering project, and Curtis approaches it with the kind of deliberate measuring that makes a major structural modification easy to follow. Before reaching that stage, he finishes the mast support plates, dealing pragmatically with discrepancies introduced during laser cutting and pressing. Grinding the plates to fit, filling the remaining gaps with weld, and postponing cosmetic weld cleanup keeps the work focused on fabrication rather than presentation.
The decision to tackle the rear differential before the front is well explained. Raising it exposes a chain of packaging problems involving the engine, sump, hydraulic pump, transmission, transfer case, suspension travel, and eventual engine-mount position. That dependency gives the project a clear sense of progression: this is not simply a matter of moving an axle upward, but of discovering how one geometric change affects several other systems.
Preparation around the differential is particularly satisfying because an old problem turns out to be easier than expected. The previously cut lower-control-arm bolts come out without the anticipated fight, revealing that they had been seized in the control-arm bushes rather than the differential mounts. From there, Curtis centers the differential, establishes reference points and determines that it needs to move upward by 70 millimeters. Cutting 100 millimeters of chassis clearance instead provides additional room for differential and suspension movement, with final ride height intended to be controlled through the suspension and a bump stop.
Attention to fabrication details gives the chassis modification more substance than a simple cut-and-fit sequence. Curtis rejects his initial 45-degree layout when he does not like its appearance, checks the control-arm mounting positions for parallel alignment, and uses a 50-millimeter annular cutter to create radiused corners intended to reduce the likelihood of cracking. A guided gas-axe cut then removes the remaining material before the edges are cleaned with a sanding disc. The combination of measurement, explanation and visible revision makes the reasoning behind the finished opening understandable.
Reinstalling the engine provides the episode’s most useful reality check. With the differential raised, the expected interference issues become tangible: the sump contacts the differential, while the hydraulic pump contacts the rear of the crane. Curtis outlines a proposed solution involving reversing the sump orientation again, replacing the previously modified oil pickup tube, and lowering the engine by roughly 150 millimeters. He also notes that the engine has already been moved rearward by about 600 millimeters, illustrating just how interconnected the rebuild has become.
The main limitation is that the episode stops at an intermediate stage rather than proving the new arrangement works as a complete system. The Allison 2500 transmission has been ordered but has not arrived, and the transmission and transfer case need to be fitted before the engine mounts can reach their final positions. An offer from the transmission supplier to provide an empty housing should allow fabrication to continue, but viewers are left with several important clearances and final mounting decisions unresolved. The closing collection of outtakes adds personality and some workshop humor, though it extends the ending after the substantive project update has already concluded.
Pros
- Clearly explains why the rear differential must be addressed before continuing with the front.
- Shows the measuring, layout, radiused corners, cutting and cleanup involved in modifying the chassis for additional differential clearance.
- Demonstrates how raising the differential creates interconnected clearance issues with the engine, sump and hydraulic system.
- Revises the fabrication layout when the initial geometry is unsatisfactory rather than simply proceeding with the first plan.
- Provides useful measurements, including the 70-millimeter differential raise, 100-millimeter clearance cut and approximate 150-millimeter engine lowering.
- Keeps unresolved transmission and engine-mount dependencies explicit instead of presenting the modification as finished.
Cons
- The transmission delay prevents the episode from reaching final engine positioning or demonstrating the completed drivetrain packaging.
- Several important solutions, particularly the hydraulic-pump relocation and final suspension setup, remain undecided.
- The extended outtake sequence is entertaining but adds considerable material after the technical portion has effectively ended.
A potentially confusing collection of chassis, suspension and drivetrain modifications is presented as a logical sequence of measurements, cuts and clearance checks. Although the unfinished transmission installation means this chapter ends before the new configuration can be validated as a whole, the careful fabrication work and transparent problem-solving make the intermediate progress worthwhile.
