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Frame cracked questions

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I have 3 ed mack 2 2000 and 1 2001 why do everyone of these trucks frame crack at the back by the rear end running the long way ..dot told me park it dont lif it back on the road its dangerous smh

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If you are talking cracked at the frame flange bend, top or bottom it is generally rust spreading a double frame, or even on a single frame at the trunnion stand at the bottom.    terry:MackLogo:

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+1 on the rust, gotta disassemble frame, sandblast and paint before it gets to cracking point. You could probably still take it apart and weld it back together if it's the horizontal flange crack by the trunion. Mack frames want 100,000 pound tensile welding rods, 3/32nds for frame repair. I think 10018 rod? Took my dad and I about a week and a bit to do our 95 rd. Well worth it, but we didn't have any cracks yet.

Because the DOT caught you you might have to show them the truck to be put back on the road, or sign that it's been fixed.  Once it's been welded, bring it so you can't tell it's been welded.

Edited by JoeH

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Note that I said gotta disassemble BEFORE it gets to cracking point.

3-5k per rail. So you're looking at 12-20k if it's a double frame, just in rails. Add in 1k in bolts, a few likely broken crossmembers, you're looking at 25k. If your rails are still good like ours were in the last one we did, why take on the extra expense?  Our truck only gets 5-10k miles a year, never in salt, so we're going to get a few decades out of our rails.

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13 hours ago, JoeH said:

Note that I said gotta disassemble BEFORE it gets to cracking point.

3-5k per rail. So you're looking at 12-20k if it's a double frame, just in rails. Add in 1k in bolts, a few likely broken crossmembers, you're looking at 25k. If your rails are still good like ours were in the last one we did, why take on the extra expense?  Our truck only gets 5-10k miles a year, never in salt, so we're going to get a few decades out of our rails.

A dumb question Im sure, why do you use new bolts ???

I just bung the..back in and so far therehas never been a drama 

 

Paul 

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52 minutes ago, mrsmackpaul said:

A dumb question Im sure, why do you use new bolts ???

I just bung the..back in and so far therehas never been a drama 

 

Paul 

I didn't know they cost that much,shop that works on my truck said he could replace my rails for ten thousand installed,to late to take mine apart,23 years in NY and plowing snow takes its toll..

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While the "body bound" bolts are the best to use by far, I've used these for many years on both mine, and other's repairs when stretching or relocating frames/parts without issue. I do use a "Hougen" magnetic drill with the correct annular cutter for the fastener and it's much less expensive than the other fasteners:

image.png.5e5aaadcd81ab915022026b2f12f5f73.png

image.png.809647be1be27530c52432d4a2e36841.png

image.png.238949502a4f293acd4754b1a09b68db.png

 

 

While it may not be right or the best way it's worked for a lot of years for me.

image.jpeg.1ce4d967a23a336848fc9ba0061b46a6.jpeg

image.jpeg.6446e437cf70eb0501675b159b0696b3.jpeg

image.jpeg.16484c6176d241194fe6dbc2fed3b6ff.jpeg

 

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Whilst Im not questioning how accurate the information is here at a quick glance at Mrs Mack I cant help but notice she only has normal grade 8 bolts at best on her chassis 

 

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4 hours ago, mrsmackpaul said:

Whilst Im not questioning how accurate the information is here at a quick glance at Mrs Mack I cant help but notice she only has normal grade 8 bolts at best on her chassis 

 

Grade 8 is right, but Mack frames are assembled at the factory with "body bound" fine thread bolts, which are an oversized bolt in an undersized hole. 

All suspension, crossmembers, steering, cab mounts, fuel tank brackets, etc etc should be body bound bolts. Air valves and relays etc can be whatever the heck you want.  I had an 01 Mack tractor that used "Huck" bolts for the air ride suspension. They're an approved alternative in some cases I assume.

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I wonder if Australian built Macks just used normal grade 8 bolts as Australian content was very high 

All spring hangers, fuel tank brackets, air tank brackets, bonnets (hoods in the US) were all made in Australia 

No doubt there was countless other bits as well 

At a guess thats why we dont use the flash bolts used over there

 

Paul 

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