Cracked Frame

[jeffl1107]

Hey Guys,

Need some advice and ideas. I'm very nervous about this. You probably heard me mention this in another posting a while back but could not find it. Anyway, I have a 97 Mack RD688S Tri Axle Dump Truck. Unfortunately when I bought it about 8 months ago, I did not look over the truck as good as I should of and got the shaft big time. It had a complete crack threw both sides of the double frame. How it happened I have no idea cause obviously the jerk I bought it from never mentioned it. There was a fish plate on the inside spanning about 2 feet in front and about 3 feet behind the crack. The crack is right where the lift axle bolts onto frame so it was hard to see especially when it was doctored up, but definitely not fixed. I had it repaired by a guy that I have confidence in as he has done these kind of repairs before. But because of where it was located he said he could not guaratee it with the lift axle constantly putting pressure and flexing the rails everytime it is engaged. He told me he V grooved the cracks, put in a root weld and then welded it up. He also said he let it cool down slowly. Not a welder so not sure, but that is what he did.

So, I am up for any advice as to what I can do to try and fix this permanently short of replacing the frame rails cause I know that is a huge undertaking and the truck probably is not worth it. The problem is I know I cant keep having this welded because I heard of metal fatigue and then from what I have heard, I am screwed if it gets to that point. To my knowledge, not knowing what the owner did, although the guy I had do it said when he took the fish plate off the inside, he saw no welds, so I think his was the first weld on it. The fish plate on the inside is the same stuff the frame rails are, just the next smallest size to fit inside. It is bolted on in several places with the lift axle bolts and some others. I was wondering if that plate was seriously beefed up, if that would help things, maybe not letting that area flex as much when the lift axle is engaged. Any ideas???

Forgot to put in that my reason for asking for help is that it was repaired about 5 months ago by the guy. Last two loads I did yesterday I heard a slight vibration going around slight turns with lift axle down. No, it is not steerable but just going around slight turns on highways. When I was fueling up I looked in the area of where the cracks was welded and noticed that there was about a 4 inch crack there. So I caught it before it went real far, but the frame is already starting to sag on that side so I dont know what to do.

[Rob]

It sounds like your welder was on the right track. The interior fishplate is good and bolted securely is good. I'm certain he used a good quality material when making the repair as far as filler. Citing that he "Vee" grooved the frame and made a root, then a finish pass about the only thing left that could have been done is to stress relieve the weld zone. This can be done with a torch and temperature indication crayons that turn color when the proper temperature is reached.

There is a lot of induced stress in the area you mention with a lift axle. I've seen a lot of breakage and welded up a few. A fishplate is the best insurance against this happening again and this measure has been taken. Just use plenty of bolts to secure it.

Rob

[hatcity]

Possibly plate the outside frame also.

Question- What is the air pressure you have the lift set at?

If it is too high, it is taking ALOT of the weight from your drives. Not to mention the steer axle.

[oldmacktrucks]

I remember your truck in your last post, I believe it was a brown slant nose RD if I recall, however when you asked for help last time you posted that you purposely withheld critical info while trying to rack our brains for help...like it was a test for us...I dont mean to be rude but when you have guys that are pitching in to help you its not polite to test us on our knowledge. As with that being said, yes I would fish plate your frame, or if you really wanted to do it right buy a set of rails for your truck and re-rail the broken side, but thats a lot of work. A good welder...and I mean good (I'm sure you know the difference) can repair those rails...I've stretched trucks since I was 15 and NEVER had a chassis crack. What I would do if you have the time is remove your outer rail, weld the inner rail, the splice the outer rail 3 foot forward of your crack and you should be fine, but once again this will require at least one new outer rail. -Sean

[jeffl1107]

First, yes Sean, you were correct about my original post and I apologize for that. I should not have done that and just given all info. My fault, Sorry!

Everyone seems to have good ideas. I do like your suggestion Sean, but not sure I exactly follow you. It does not seem like you are saying to replace the whole outer frame rail but dont know exactly what you mean by splice it 3 ft forward? Are you saying to actually cut the outer rail away, weld the inner rail and then put a new pc. in welded 3 ft. away from crack on either side to help relieve stress that is right under the lift axle bracket? If not, could you explain a little further. And if you are saying to replace the whole outer rail, do you have any experience with how long this might take to accomplish removing and installing new one. I consider myself pretty mechanically inclined and know just from looking at it that it seems to be an immense amount of work.

Also, I am running about 75psi in the lift axle. When it is engaged you can fell it slightly raise the truck up but that is what I have been told by several guys to run it at.

Also, the welder was going to put something on the outside, but decided against it. Two reasons. First because the lift axle bracket is right where the crack is. Second, he was unsure of the regulations and wanted to know if I got stopped by DOT and had something welded on the outside of the frame, if that would constitute failing the inspection. He said with other cracks in frame rails he has repaired, he never had to weld anything onto the outside, but in this case, it might be necessary to end this problem.

[vision386]

Hey Jeff,seems like this is an ongoing problem,i usually don't recomend a specific shop or service unless i have used them, or really value their opinion,but in this case,me personally i would give these guys a call,see what they recomend,my dad,myself have used them for many years for frame,spring,front-end repairs etc.Dam quality jobs at fair prices!....just a thought!........Mark

Circle Spring and alignment

5 Mill street

Elmer,NJ 08318

(856) 358-0404

[oldmacktrucks]

First, yes Sean, you were correct about my original post and I apologize for that. I should not have done that and just given all info. My fault, Sorry!

Everyone seems to have good ideas. I do like your suggestion Sean, but not sure I exactly follow you. It does not seem like you are saying to replace the whole outer frame rail but dont know exactly what you mean by splice it 3 ft forward? Are you saying to actually cut the outer rail away, weld the inner rail and then put a new pc. in welded 3 ft. away from crack on either side to help relieve stress that is right under the lift axle bracket? If not, could you explain a little further. And if you are saying to replace the whole outer rail, do you have any experience with how long this might take to accomplish removing and installing new one. I consider myself pretty mechanically inclined and know just from looking at it that it seems to be an immense amount of work.

Also, I am running about 75psi in the lift axle. When it is engaged you can fell it slightly raise the truck up but that is what I have been told by several guys to run it at.

Also, the welder was going to put something on the outside, but decided against it. Two reasons. First because the lift axle bracket is right where the crack is. Second, he was unsure of the regulations and wanted to know if I got stopped by DOT and had something welded on the outside of the frame, if that would constitute failing the inspection. He said with other cracks in frame rails he has repaired, he never had to weld anything onto the outside, but in this case, it might be necessary to end this problem.

If you wanted to splice the frame the right way, you have to stagger the welds...in other words you would have to replace the outer rail 2 to 3 feet forward of the crack on the inner rail, so to do this you would have to cut the outer rail 2 to 3 feet forward of your cracks now, remove the outer rail (from the cut point back) and replace...its a lot of work to do it right

[oldmacktrucks]

If you wanted to splice the frame the right way, you have to stagger the welds...in other words you would have to replace the outer rail 2 to 3 feet forward of the crack on the inner rail, so to do this you would have to cut the outer rail 2 to 3 feet forward of your cracks now, remove the outer rail (from the cut point back) and replace...its a lot of work to do it right

Yes the outer rail would have to be replaced from the point where you cut it all the way to the back of the truck.

[cgallamore]

it really sucks, because it doesn't matter what you do it allways there haunting you....

[jeffl1107]

Ok, got what you are saying now Sean. Yeah, that is alot of work. Have to see what we decide to do here.

Thanks for the contact Mark. I will give them a call and see what they say.

[jeffl1107]

You got that right. Everytime I pull out with a load, EVERY TIME, I think of that crack.

[bobo]

You got that right. Everytime I pull out with a load, EVERY TIME, I think of that crack.

hey the pictures in your profile, are they of the frame in question? with the welds and small rectangle on the top of lift axle mount? bobo

[MidniteMechanic]

The old owner probably didn't dump the air on the lift axle all the time when turning. The only way to fix it is replacing the rails. It will crack again along the welds.

[bobo]

The old owner probably didn't dump the air on the lift axle all the time when turning. The only way to fix it is replacing the rails. It will crack again along the welds.

Yes Midnite Im with you! IMHO when ever you have a hanger, whether its spring or air. THERE HAS TOBE A XMEMBER! or it will crack time and time again! put new rails on and it with crack again! I can remember when I work for Mack, we were replacining Xmember on RB's and RD's dump trucks all the time. Thats when the % peice Xmember came out. bobo

[cgallamore]

You got that right. Everytime I pull out with a load, EVERY TIME, I think of that crack.

if it was mine i would replace frame rails or get rid of the truck...........

just my opinion........

[fifth wheel]

Your frame is about to fail, when it does the cab shield will come down thru the cab, any cracks is OUT OF SERVICE.

FW

[Lmackattack]

I looked at the pics in your profile and if thats the crack in the rails....that dont look good. sorry to say. Looks like you broke both frame rails in the same spot. thats the worst of the worst. All thats really holding it is the 3rd inner channel. And yea when it lets go that side of the truck will likely sag pretty hard if your loaded. Personaly I would not drive that truck other than on site. and I have been known to be a risk taker....At a minimum you should replace the outter rail but at that rate you might as well replace both while in there. You can jerry rig it to get by for a little bit but it needs attention. The biggest issue I see is that both cracks are in the same spot. the 2 weak spots are in the same location and that 3rd channel is basicly doing all the work. I have seen a few cracked frames that held up just fine in a tractor but they had a inner channel that ran past the crack to the first crossmember on each side of the crack. When I have seen double frames crack it was either the inner or outer rail. not both. If you only had one rail crack you would get by with a good welder and a added "3rd" inner channel ran to the nearest crossmembers each side of the weld.

just my .02

Trent

[theakerstwo]

I think 75 psi is too much air pressure. Any way around here we are only allowed another 5000 lbs per air lift.I have two lifts and have sacled them and at 48psi i am carring 7000lbs per axle.I saw a axle this summer that was not very old break up bad. I ask him how much pressure and he say dont know cause no gauge. We get to looking and he not got a regulator also.And a nosteer axle is only asking for frame problems over time.

[Lmackattack]

I know at work the air ride trailer has a regulator valve for the bags and I think it says not more than 40psi? But it all depends on the size of the air bag and what it needs to lift. I agree that 75 psi sounds kinda high.

[cgallamore]

in MO. in the heavy zone you are allowed 22,400 lbs per axle always carried around 80 psi. on my 3rd axle

never had any problems, but you can't ride around smoking pot and blaring the radio, while grossing 96,000 lbs. i allways tryed to keep it under 110,000 on a straight truck. you have to pay attention at all times.

i hate steerable, they will f#$k you up trying to back up in the soft stuff.

as son as they touch anything they turn sidways and dig in.

i don't think they make a 22,000 steerable...

[gearbox]

I'm with Midnite as the rails need replacing and a x member added to help strengthen, those rails are not pretty big job but it is the only way to fix this truck gearbox

[jeffl1107]

Your opinions are much appreciated. Obviously your right about the best thing to do is replace the frame rails. Just wondering how long you think it would take 2 mechanically inclined guys to replace them. I heard the rails are only $1500 so no big deal. But my problem would be the down time. I guess I would have to someway support everything mounted to the rails and figure out a way to take the weight off that side of the dump body. I have so much money into this truck, I really dont want to get rid of it. And, yes, the pictures you saw are that of the cracks before it was welded.

I know that replacing the rails is the best way to go, but you dont think seriously beefing up the inner channel (fishplate) would work??? Just wondering. It really sucks where it is because everytime I engage that lift axle it is putting stress on that cracked area. I dont know what the previous owner did to crack both frames, he never would tell me after I found it. I am trying to go after him legally but probably wont get very far.

[theakerstwo]

in MO. in the heavy zone you are allowed 22,400 lbs per axle always carried around 80 psi. on my 3rd axle

never had any problems, but you can't ride around smoking pot and blaring the radio, while grossing 96,000 lbs. i allways tryed to keep it under 110,000 on a straight truck. you have to pay attention at all times.

i hate steerable, they will f#$k you up trying to back up in the soft stuff.

as son as they touch anything they turn sidways and dig in.

i don't think they make a 22,000 steerable...

A steerable needs to be lifted to back up unless it has the back up kit which just reverses the caster when the trans sees reverse in gear.In the dump trucks here they weigh like my truck has two lift so they weigh the rer most four in a group which is the inter bridge nd the front to the rear as outer bridge. Its same as the Federal bridge law.So a 24 ft bridge with 5 axle will gross 63000.But some guys will weigh you per axle and try to ticket you for being over per axle even if your in side the group weight. No standards here with the DOT.They dont want to shut you down but only get some extra change off of the trucks.I am told it going to get worst because one DOT cop said they are starting to find those that cant stay with the GVWRating front factory.

[bobo]

Your opinions are much appreciated. Obviously your right about the best thing to do is replace the frame rails. Just wondering how long you think it would take 2 mechanically inclined guys to replace them. I heard the rails are only $1500 so no big deal. But my problem would be the down time. I guess I would have to someway support everything mounted to the rails and figure out a way to take the weight off that side of the dump body. I have so much money into this truck, I really dont want to get rid of it. And, yes, the pictures you saw are that of the cracks before it was welded.

I know that replacing the rails is the best way to go, but you dont think seriously beefing up the inner channel (fishplate) would work??? Just wondering. It really sucks where it is because everytime I engage that lift axle it is putting stress on that cracked area. I dont know what the previous owner did to crack both frames, he never would tell me after I found it. I am trying to go after him legally but probably wont get very far.

Replacing the rails will not solve the problem! you need a cross member on or slightly ahead and on or slightly behind where the lift axle hangers are. doesnt matter if its a steerable or not you need cross members! look at other truck and get back too me! the b0bo!

[Lmackattack]

To replace the rails is a pretty big job. I would remove the box First so you have room to work. then you want to put it on very level ground and use lots of jack stands that can support the weight so the truck and the drivetrain. I would figure 2 guys can get all the bolts out in a day and Hopefully have it ready to pull the following. If you can get stock rails that have the holes pre drilled your golden. If that is the case than all you need to do is remove the bolts slide it out,drill a few holes for any of the aftermarket items. and slide in the new rail. figure a solid week if you can work on it for 8-10 hrs every day and run into few issues. I Never have done a rail job but have taken a truck down to the rails a few times. I think the hardest part will be supporting the truck when the rail is unbolted. Also Check and see if this truck has huck bolts. if it does I cant comment as I have never removed hucks.