U225X PUBLIC-SAFE CONVERSATION NOTE

RECORD: CHAT-0383
TOPIC: Truck Mount Dimensions
IMPORTED: 2026.09.01

This note was generated from a matching conversation in the supplied ChatGPT export.
EXTRACTED REQUEST: give me everything dimension wise on the 2500 truck we are designing a bed for I just got done measuring the mounts and there are 8 total 3 sets on the outside of the frame and 1 set on the inside of the frame the inside ones are center to center of 3/4" hole 32.625, the nest closest to the cab is on the outside at 48 center to center of 3/4" hole the next closest to the cab are 47 3/16 center to center of 3/4" hole 

RECOVERED CONVERSATION EXCERPTS
USER MESSAGES:
1. give me everything dimension wise on the 2500 truck we are designing a bed for I just got done measuring the mounts and there are 8 total 3 sets on the outside of the frame and 1 set on the inside of the frame the inside ones are center to center of 3/4" hole 32.625, the nest closest to the cab is on the outside at 48 center to center of 3/4" hole the next closest to the cab are 47 3/16 center to center of 3/4" hole and the closest to the cab are also 47 3/16 center to center of 3/4" holes. starting from those hol…
2. that is correct. Is ther eanything you can cross reference these numbers with to make sure I am pulling accuratly
3. One thing that gets me is this, notice how the holes at the left side of this drawing would be in the tube? this model shows out to out of tube at 37.8 what does the manufacturer say about that? also i should have another inch or two past the last hole before the fram starts turning into the bumper

ASSISTANT RESPONSES:
1. Yes — this makes sense, and with the axle reference you gave me I can actually tie almost all of the mount locations back to the cab. I’m treating the back of the cab as X = 0, measuring rearward, and the truck centerline as Y = 0. I’m also interpreting your statement that the 2nd mounting pair from the cab is 21.5" from the axle centerline as 21.5" forward of the axle. Since cab-to-axle is 42.5", that puts that mounting pair at X = 21.000". | Feature | Longitudinal X from back of cab | Hole spacing across truck | Hole Y from centerline | |. |. :|. :|. :| | Mount Pair 1 – closest to cab | 4.375" | 47.1875" (47-3/16") | ±23.59375" | | Mount Pair 2 | 21.000" | 47.1875" (47-3/16") | ±23.59375" | | Rear axle CL |…
2. Yes. I can cross-check your field measurements against published 2022 GMC Sierra 2500HD chassis/cab dimensions, GM upfitter/body-builder data, and any available frame/mount drawings. The most valuable checks will be cab-to-axle, rear overhang/overall bed envelope, frame width, and whether the OEM bed-mount stations line up with your four measured pairs.
3. Yes — this screenshot exposes something important, and I would not change your measured hole pattern. I think the downloaded truck/frame model is wrong in the rear-frame geometry. Look at what your drawing is telling us. Your rear/inside mounting pair is 32.625" C-C, so each hole is only: 32.625 / 2 = 16.3125" from vehicle centerline. But your model has the frame at that location at roughly 37.80" outside-to-outside, or: 37.80 / 2 = 18.90" from centerline. So a hole at Y = 16.3125" lands about: 18.90 − 16.3125 = 2.5875" inward from the outside edge of the modeled rail. That's exactly why those Ø.750 holes appear to be sitting inside the rectangular tube/frame rail in your drawing. I don't think your measuremen…

EXTRACTED KNOWLEDGE / HOW-TO
- Pair 1 → Pair 2 = 16.625"
- Pair 2 → Pair 3 = 42.125" (42-1/8")
- Pair 3 → Pair 4 = 18.5625" (18-9/16")
- Pair 1 → Pair 4 = 77.3125"
- Pair 4 → bumper rear = 9.8125"
- Axle → Pair 1 = 38.125" forward
- Axle → Pair 2 = 21.500" forward
- Axle → Pair 3 = 20.625" rearward
CONVERSATION SHAPE: 3 user turns / 5 assistant turns
ATTACHMENTS DETECTED: 10

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