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jeffl1107

Differential Weight

16 posts in this topic

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.

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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.

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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.

400 lbs. does seem a bit light, but you will be OK with a 2 ton hoist. Done it myself 12 years ago I don't think they have gotten any heavier.

Gregg

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2 ton hoist will work fine, dont forget the 2 bolts inside the side cover :thumb: Are there metal shavings on the magnetic plugs? Before you pull it all apart I would check for shavings, loose yokes in the jack and main shafts, bad U-joints etc. How many miles did you put on it with the power divider locked?

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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.

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Vibrations are a nightmare to find on a Mack...usually its trial and error, been there done that. You can jack the truck up and block it in the air, run it thru the gears and try and pinpoint where the noise / vibration is coming from with the truck actually running and driving "in place" sounds hairy but we do it all the time. It just sucks to be pulling everything apart. You might just have to rebuild the power divider and not the whole rear. :MackLogo:

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I thought all mack rears had the Power divider on the forward rear only? if you want to rebuild the power divider you dont have to pull the diff out. But if the diff has to much play in it than you might as well pull it out.

Vibrations are a PITA to locate. Drive shaft,tires, power divider, cab mounts, shocks, even the throttle return spring can cause engine serge and cause vibrations. I have also heard that the camelback rears seam to cause a issue with the axels bouncing and fighting each other.

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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!!!

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I think I would have to go KICK SOMEONE IN THE NUTS REALLY REALLY HARD. Man I hate to hear something like this.good luck :( Thank God you found out before it did any more damage.

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I've heard of mismatched ratios being very close so that under normal circumstances there was no problem, but engaging the power divider would cause all kinds of problems.

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***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.***

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It sounds like your mechanic thinks the noise may be coming from a bearing, maybe the clutch release bearing or the pilot bearing in the flywheel. When you changed out the rear ends did you remove the wheel bearings and clean and inspect them? They share the same oil as the rear ends, so the debris that was found in the rear end was also running through the wheel bearings. I have seen several geared components rebuilt by "rebuilders" that were as bad or worse than the component that was removed.

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If you replaced the rear rear and used your original yoke its possible your yoke had a wear sleave on it, if it did and you have a stock OEM seal on your rear the yoke is going to shread the seal apart in time and your going to have gear oil slinging everywhere, I know it happened to me. If not it could just be a bad seal or a vent cap clogged on the rear. As far as your noises go, I would block the truck up in the air and run thru the gears with someone listening to try and pin point where they are coming from. Sounds dangerous but we do it all the time and never had an accident (knock on wood) Before you go broke, and or insane...maybe its just something to let ride and see what happens, I mean everything is new and should be covered by who ever you got the re-mans from. Macks do make noise and vibrate...and it is not easy or cheap to find out why. My point is you could spend another couple grand and still not get it right. To pull the whole drive train apart in my book is way more expensive than just running it and repalcing whatever (if anything) when it fails. :MackLogo:

post-7064-047016700 1291905806_thumb.jpg

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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.

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