Hi everyone, saw this was stickied, wanted to ask if anyone here has done this swap on their GMT400 truck. And if you were able to directly swap the entire bushing and mounting hardware from the GMT900 to the GMT400 platform without any modifications.
Edit: This is from Aloicious's write up in 2011 on this swap, it's probably what I am looking for:
I had some rust that was preventing the new mount from sliding in very well, and the paint on the mount itself was also pretty thick and preventing it from seating, with a small grinding tool, like a dremel, I cleaned the hole in the frame, and removed some of the paint from the mount itself, it was still not going in well, so I clearanced the hole just a tiny bit, it’s likely you will need to do the same, just be aware not to take too much material off, you want the mount to fit snugly in the hole. Here you can see the upper mount fitting through the frame hole correctly:
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My guess is the hole was actually just smaller than the intended holes on GMT900 frames.
The mounts that I want to put in are from S&B Filters, they're silicone rubber. They're supposed to have the ride quality of brand new OEM rubber or better, and last the lifetime of the vehicle. I don't want to go with Daystar/Energy Suspension/Prothane and have the truck rattle like a SOB and the rubber options from Dorman and LMC have longevity problems from what I've read on the forums. These S&B mounts are not cheap, but I love one and done solutions that work and work for a long time.
S&B let me know the frame holes on our GMT400s are smaller than the later vehicles and that they advised not to alter the frame holes to make their bushings fit. Looks like they were spot on. Not sure what I'll do in the interim. The mounts aren't 100% shot yet but I'm taking the cab off soon.