slug Posted February 19, 2018 Share Posted February 19, 2018 Hi guys, looking at a 1985 Mack R model 686. The guy selling is practically giving it away so the question I have is more about how to fix vs. should I buy it. The frame is cracked at the same location on both sides of a double frame tri axle. Crack is about 12 inches long between the rear drive tires at bottom of frame. Any thoughts on what the fix would be? Better to replace the entire frame? Pictures of cracks below. Quote Link to comment Share on other sites More sharing options...
Truck Shop Posted February 19, 2018 Share Posted February 19, 2018 (edited) It had a small crack and then the rust got to it between the rails. The best way is to drop the suspension, cross-members and remove the inner rails. Cut the frame at the cleanest spot and replace outer rail and install new inner rails. 80,000 material for replacement rails. A bunch of work but it depends on the shape of the rest of the rig. If it's rough it might be a pass. Problem is when you pull the inner rail out you will probably find thin spots all through what's left of the main rail. Truck Shop Edited February 19, 2018 by Truck Shop 2 Quote One ping only Link to comment Share on other sites More sharing options...
slug Posted February 19, 2018 Author Share Posted February 19, 2018 34 minutes ago, Truck Shop said: It had a small crack and then the rust got to it between the rails. The best way is to drop the suspension, cross-members and remove the inner rails. Cut the frame at the cleanest spot and replace outer rail and install new inner rails. 80,000 material for replacement rails. A bunch of work but it depends on the shape of the rest of the rig. If it's rough it might be a pass. Problem is when you pull the inner rail out you will probably find thin spots all through what's left of the main rail. Truck Shop Thanks Truck Stop. Yeah, that sounds like a fairly big job. I think I was kind of hoping for a simple, quicker fix but I guess that is what we all "hope"for. haha. Anyway, thanks again. Quote Link to comment Share on other sites More sharing options...
Hobert62 Posted February 28, 2018 Share Posted February 28, 2018 Maybe this would help https://pennstate.craigslist.org/hvo/d/frame-from-2007-mack-triaxle/6509516485.html Quote Link to comment Share on other sites More sharing options...
MACKS Posted February 28, 2018 Share Posted February 28, 2018 How bad is the rest of it,any more pictures,what are u gonna use it for,that crack is due to rust spreading the flange not stress or fatigue,seen way worse than that still working .. Quote Link to comment Share on other sites More sharing options...
mackr1989 Posted March 6, 2018 Share Posted March 6, 2018 we bought a 2000 rd with 58s last year and the frame had some scale between the rails. i started hitting the frame one day with a sledge to break some of it up and 1 foot hair line cracks started appearing. replaced the rails at donovan in nh for $11k. touch up paint hides a lot when youre selling something... Quote Link to comment Share on other sites More sharing options...
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