jeffl1107

You all have good suggestions. I have a guy that is welding something in but as you all think, and same with me, dont think what he is doing is near enough. I tried to get it threw his head that I could have upwards of 28 ton of material in the body and the added factor of the lift axle being right where the crack is going up and down constantly. I have adjusted my psi to 45 now. I just dont have the money right now to do a complete rail changeout. Mack dealer said it would probably be around $11,000. I know there are guys out there that can fix this problem, but finding them here in NJ seems to be like finding a needle in a haystack. There are a few guys that seem to talk a good game, but I dont think they have had experience with doing this. The welder doing some work now wants to weld in a 3/4" thick elongated diamond shape on the inner rail. He said that is how they do it when they stretch frames. But just doing that I told him is not enough. I was wondering if that was done, then adding a piece of C channel the next size bigger on the outside of frame on both sides to be bolted on and tied into the crossmemebers, if that would do the trick. I dont have the welder or the expertise to do this, and just cannot seem to find anyone that I trust to repair this once and for all. Maybe even purchase a crossmember from Mack and add that right in the middle of where the lift axle bracket bolts on. I mean I know there are guys out there that stretch big truck frames. Has to be someone around that can fix this correctly

Hey Guys, Well about the cross members. There is 1 cross member about 16 inches in front of the crack. It is just behind where the mounting bracket is for the dump body ram. On the other side of the crack, going towards the back, there is a cross member about 2 1/2 feet behind crack. And no, the fish plate that someone else had put in there that is still there, is cut to fit in between those 2 cross members. In order to get a piece that extends past each of those two cross members, I guess that would mean I would have to take them out, cut them down the thickness of whatever plate I would use and weld them back together??? I did find out that I was wrong about the price on the rails. I was told by some dumb a** that they were $1500. They are $3500 for ones from Mack Dealer. I took a long look at the truck today. My only problem would be getting the dump body off. That is not in my capability at my house. This thing is driving me crazy. I just dont have the cash to go out and buy another truck. I either have to figure a way to get this fixed right or try and sell it off to get into another truck. Dont know what I should do. It sucks cause I have plenty of work for the truck, just dont know if it is going to give me a problem. The only good thing I have going is that when I have a load on, when the lift axle is down, it is actually supporting that cracked area as the bracket for it is almost dead center of the crack. My only problem is trying to keep the truck from bouncing around when I get to the dump site loaded where I cant have the lift axle down. I would like somehow to get this welded up so it is ok but if I have to replace the rails, I will have to seriously think whether the truck is worth it or not. Right now it is my livelihood, but replacing the rails is a good deal of money and a good deal of down time, which neither of them I can afford.

Hey guys, Was not sure where to put this so hope it is ok. Wondering if any of you guys know if there is somekind of valve on a hydraulic piston that lifts the dump body on a dump truck somewhere that can control how fast or slow the dump body comes back down after i dump a load. Right now it takes forever to come back down. I just had everything rebuilt about 5 months ago. Just wondering cause I would like to speed it up if possible. Thanks, Jeff

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.

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

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.

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.

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.

Forgot to mention, put new yokes on rears when I changed the rears

Yes, all the bearings and races were checked and seemed to be good. So here is where I am at now. The mechanic came over. He took about a 1/2 hour ride with me. He said he hears no noises that would indicate any major problems. What he did hear is very odd noises coming from the air dryer. I have had problems with it for a while but left it go because it was still purging off the air. What mine is doing is when it purges the air, instead of purging and shutting off, it purges and then goes another 10 to 15 seconds just mildly spitting off a little air and then shuts off and does it all over again. Well in that extra 10 to 15 seconds, it has been making some ungodly noises. And I have also been having some issues with my compressor. It has been leaking. And, the mechanic said it is also making noises and that is probably what I am hearing. But, I asked him, how does that explain the vibration noise that just started when I get to 65mph. He could not say as, of course, it did not do it when I took him for the ride. It just did that the last time I was on the road and I was loaded when it happened. He went over the truck and he found nothing loose. So, I replaced the air dryer yesterday but I am having him come over tomorrow to replace the compressor. Then, have to hope that cures the problem. I was wondering if it could be a drive shaft but I looked at all of them and the weights are all intact. And that should have nothing to do with them going out of whack with new rears and tranny, correct??? Could it have to do with 1 tire I have that is pretty much bald? Just trying to think of things it could be.

***UPDATE I was given false info by the counter guy at the shop. I found out that both rears had the 442 gears in them. So the original info. I gave in my last reply was false. The mechanic that looked at the rears said they both had same gears and another guy that gave me that info was wrong and he apologized.*** Well I replaced the inner rear and I have new noises going on so could use everyones input. If I dont end up in a straight jacket I will be surprised. We put the rear in on Sat. Ran truck Mon, Tues and today. Keep in mind, back rear put in about 3 weeks ago, then tranny about 2 weeks ago and then inner rear this weekend. Truck was not run alot during that time. On Monday I was hearing a noise. Hard for me to explain these noises but will try. 3 noises all together. One is a whine noise, not real loud but definitely noticeable. Second is like a cha, cha noise while I am running down the road, seems to go with the rpm of engine, but not positive with that. The third noise just started yesterday on the last load of day. It only happened when I got to around 65 mph. It was like a grrrr noise. and it would start out soft and get louder. As soon as I backed off the fuel pedal, it would go away. But most of the time when I got back up around 65 it would come back until I again would have to back down. So, anyone have any suggestions. I am about at my wits end with this thing and need to figure out what is going on before it puts me under. The one guy, a certified mechanic that works for a fleet truck company that does this work on the side, that put the tranny and back rear in said it could be the tranny or clutch. I dont see the clutch making this kind of noises and dont why he would say the tranny unless he thought the Reman I got is bad. I asked him about taking it to a shop, but he said noises can be next to impossible to diagnose. He said maybe it would be better to let this one ride itself out until something goes so I know what it is. I dont like that suggestion to much. I would like to figure this out before I have something go and possibly do much more damage than catching it early. So, hit me with what you think. I need to get this thing fixed. ***I thought I should also add this. The noises I am hearing now are NOT the same that I heard before. The guy where I got all this Reman. stuff said that the main top shaft bearings were not in good shape and both yokes were bad on the inner rear which was the last thing to be replaced. I did notice that the back rear, the one put in first after trying to eliminate the initial noises is leaking. It looks like the front seal where yoke is, is leaking and 3 bolts facing the back of rear were slightly loose. I tightened the bolts and we are replacing the seal today. But I dont see that it would be making all these noises. I was told that the problems with inner rear could have caused the seal to go bad on back rear. And inner rear was only engaged once since it was installed while sitting in driveway to make sure it engaged. It has never been engaged while moving. And I checked to make sure and both invoices for both rears have the stock 464 gears in the rears.***

Well, I took the front rear to be looked at today. I just got a call back and looks like I have now found out what has caused this whole nightmare and $12,000 out of my pocket with all the crap I have replaced. I have dealt with the same place for all the parts. My truck came with 464 gears stock. That is what came out of back rear. But today, when I brought them my front rear, I got a call, "Jeff, did you know that the front rear has 442 gears in it." I said, HS!!! The guys said, "yeah, that is most definetly what has caused this mess." With driving around with the power divider engaged for 3 months, the gears were fighting against each other and slowly started destroying each other. So, someone, for some unknown reason before I got the truck, left the stock gears in the back rear and put 442 gears in the front rear. So, WHAT DO YA KNOW!!!

I found out the front unit weighs 537lbs. I probably put about 4-5000 miles on it while it was engaged. The mechanic friend (diesel mechanic by trade) said there is excessive play in it and there are what he said above normal shavings on plug. All U joints seemed to be ok. The Rear rear and tranny have both been replaced with Reman. units. I dont know why the other mechanic that I had put these two in never questioned the front rear as the culprit. He pretty much went by what I was saying and took a stab at what it was. So, almost $10,000 later, still have same noise. When I decelerate, it is like a pulsating vibration noise. I know that both units were on there way out anyway, but probably could have gotten some more time out of them. Towards the end of the day when I last ran it, it got so bad I had to take it out of gear and use all brake to slow down as I thought it was going to rip the truck apart. It was pretty bad. It kind of started making the truck jump a little like a bucking kind of. I do not think that it is any of the drive shafts as the front one was put in new well before this noise started and the others seem fine along with U joints. Everyone I have talked to about this lately said that running it that long engaged, I probably screwed up bearings or something in that front rear. Instead of just getting a Reman. on this front rear, I am going to have this one rebuilt. That way, hopefully when they tear into it, they will find something that would be proof that it is the problem.

Did not explain fully I guess. I want to pull myself with a 2 ton engine hoist. The place locally said the inner differential weighs 400lbs. but my mechanic friend seems to think it should weigh more than that.

Hey guys, Well I finally found out what my vibration noise is. You guys should love this. I have been driving around with the inner rear engaged for over 2 months. Guess I must now pay the price for being stupid. The guy I bought truck from told me that the air switch on the dash is suppose to be in the forward position, towards the windshield for the disengaged position. Wrong! I never second guessed him. So I have been driving around with it in. So it was disengaged and the vibration got considerably worse, especially when I was decelerating in gear to slow truck down. But a mechanic friend told me to go slow, but engage the rear and see what happens. When I did, the noise went away. So, obviously, I have damaged something in that rear. But my main question is to save money, I want to pull it and re-install after rebuilt myself with a mechanic friend. So I am wondering if anyone knows how much that inner differential weighs. It is air activated. I believe it is 46,000lb. camel back rear.