Hook n ladder 1 Posted March 18, 2015 Share Posted March 18, 2015 My suspesnsion level is different between my drive tandems ( CH613). Its a single levelling valve but the rear axle is about an inch higher than it should be. The front measurement is right where it should be.Shouldn't both axles measure the same? I've been chasing vibration problems for years and trying to eliminate all the variables.The truck rides rough and I go through alot of shock absorbers. I get maybe 2 years out of them..I do run dump and do alot off road. Quote Link to comment Share on other sites More sharing options...
RedBullDog Posted March 18, 2015 Share Posted March 18, 2015 Can't really help on the air ride question, but I would say 2 years on shocks on a on/off road truck is really good. Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted March 18, 2015 Share Posted March 18, 2015 Check basics first. Are the tires the same hight? Are you on perfectly level ground? Check by placing a level on the pavement. Then across the tandems. Also chech ride hight loaded and unloaded. To see if your withing spec one way and not the other. Quote Link to comment Share on other sites More sharing options...
Underdog Posted March 19, 2015 Share Posted March 19, 2015 The truck may pitch to the front, causing the rear axle measurement to be higher ( meaning your frame rails are not parallel to the ground.) this could be caused by worn out front springs. or you could try a slightly taller tire on the front if you find this to be the case. In any event, the air ride height measurement it's always taken on the axle that has the leveling valve.Gregg Quote Link to comment Share on other sites More sharing options...
Timmyb Posted March 19, 2015 Share Posted March 19, 2015 I think underdog is right. Try measuring from bottom of frame to ground at front and rear and see what difference there is. My kw has parabolic springs on the front (3 big springs compared to multi leaf) and they use blocks to give the right height. Something to look at. Good luck with it. 1 Quote Link to comment Share on other sites More sharing options...
Underdog Posted March 20, 2015 Share Posted March 20, 2015 when I had my CX I added a leaf to the front spring pack for a total of 4. This greatly improved the ride and handling of the truck and front tire wear.Gregg Quote Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted March 23, 2015 Author Share Posted March 23, 2015 Thanks for the info. The truck is pitched down abit in the front (or i guess the A$$ is up..is pretty noticeable). The ride is aweful. The front drive has the levelling valve and that one is usually right on loaded and empty. Should the frame rails measure level front to back? Also i'm working on 2 other angles on my vibration problem. The rear driveshaft is missing the balancing weights. I dont know how much effect this will have on shaking the whole truck. 2nd: I think i have too much grease in the slip yoke( the front slip yoke). It looks like there isnt any movement in the yoke. My vibe occurs empty or loaded now between 25-30 mph. Quote Link to comment Share on other sites More sharing options...
j hancock Posted March 23, 2015 Share Posted March 23, 2015 If your ride heights are messed up it can change the pinion angles in your drive line and cause vibrations.http://65.170.161.218/~spicerpa/sites/default/files/pdf/driveshaft_installation.pdf Quote JimIt doesn't cost anything to pay attention. Link to comment Share on other sites More sharing options...
dogg rescue Posted March 24, 2015 Share Posted March 24, 2015 Kinda sounds like your ride height might be a little out of adjustment. How far up is the rear off the bellows? Or is your front axle springs staged out from too much wieght up front? Quote Link to comment Share on other sites More sharing options...
Dirtymilkman Posted March 24, 2015 Share Posted March 24, 2015 I made it a practice to put a new leveling valve on every two years. They can do some goofy things when they get old. Quote Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted March 24, 2015 Author Share Posted March 24, 2015 Im not sure how far off the bellows the rear is but I know its a good inch higher than it should be. This I mean an inch higher than the front drive. And like i said earlier the front is usually right on. Quote Link to comment Share on other sites More sharing options...
thomastractorsvc Posted March 24, 2015 Share Posted March 24, 2015 After redoing a Kenworth with Peterbilt suspension and learning more about air-ride systems then I ever wanted to, a few things you need to checkContact Mack and find out what the ride height is supposed to be and where it is measured from (on the KW it was measured from the top of the axle to bottom frame on other types it may be different)You need to know if all the air bags are the same (maybe the rear were changed and are different from the front or vice verse so different height)Most level valves that I have seen that control both axles are are on the rear axle (maybe your truck had two and lost one or it was replaced on the wrong axle)The drive shafts that I have messed with all have a grease hole to allow grease to escape if it suddenly needs to collapse, if the shaft is stuck more than likely it is due to lack of grease not because it has to much. If there was an abundance of grease usually it slings everywhere under the truck not freeze up slip joints. As far as weights being lost of just pull it and have it balanced while you looking at it maybe it is not in phase that can create vibration Quote Robert"I reject your reality and substitute my own." Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted March 25, 2015 Author Share Posted March 25, 2015 I did replace all 4 air bags last year. I'll check into where my levelling valve should be. But can anyone tell me if the frame rails are supposed to measure level from front back? Quote Link to comment Share on other sites More sharing options...
thomastractorsvc Posted March 25, 2015 Share Posted March 25, 2015 Call the dealer service department they should be able to give you that info without charging you Quote Robert"I reject your reality and substitute my own." Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted March 25, 2015 Author Share Posted March 25, 2015 I did. they didnt seem to understand what I was getting at. I tried to tell him the rear bags are higher not because of air pressure but maybe because the front is sagging and "pulling up" on the rear. He said the air pressure is the same in all 4 bags with 1 levelling valve. I said "I understand that" Maybe i was clear as mud. Quote Link to comment Share on other sites More sharing options...
thomastractorsvc Posted March 25, 2015 Share Posted March 25, 2015 According to Westfall Mack service dept it is 7 3/4" measured from the bottom of the frame to axle housingI asked for 1998 CH613 based from your avitar info Quote Robert"I reject your reality and substitute my own." Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted March 25, 2015 Author Share Posted March 25, 2015 Thanks for the info. I'll check it tomorrow. Quote Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted March 27, 2015 Author Share Posted March 27, 2015 I did measure. it was about 7 5/8". I wouldn 't think thats my problem. Quote Link to comment Share on other sites More sharing options...
thomastractorsvc Posted March 27, 2015 Share Posted March 27, 2015 Are both axles close to that? If so start looking at front springs.By the way what size tires are on the rear axle, intermediate axle and front axles? Quote Robert"I reject your reality and substitute my own." Link to comment Share on other sites More sharing options...
MackTech Posted April 1, 2015 Share Posted April 1, 2015 OK, at the plant I went through an issue with a truck. First off, ride height is measured from the bottom if the frame rail to the center of the spline for the yoke on the axle that the leveling valve is attatched to. You also need to find the angles of each drive axle. If they are off they can cause an issue. The angle is determined with a load on the rear with a digital protractor. Zero it on the frame rail and check the angle on a machined surface, usually the yoke spline or the part that the "straps" for the yoke bolts to.I would have the driveshaft balanced first if it's definitely missing weights, that will cause a problem for sure! Quote Link to comment Share on other sites More sharing options...
MackTech Posted April 1, 2015 Share Posted April 1, 2015 OK, at the plant I went through an issue with a truck. First off, ride height is measured from the bottom if the frame rail to the center of the spline for the yoke on the axle that the leveling valve is attatched to. You also need to find the angles of each drive axle. If they are off they can cause an issue. The angle is determined with a load on the rear with a digital protractor. Zero it on the frame rail and check the angle on a machined surface, usually the yoke spline or the part that the "straps" for the yoke bolts to.I would have the driveshaft balanced first if it's definitely missing weights, that will cause a problem for sure! Quote Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted April 6, 2015 Author Share Posted April 6, 2015 Both axles ae close to the 7 5/8 measurement. I run 22.5 all the way around. I will be getting the rear shaft balanced. Quote Link to comment Share on other sites More sharing options...
Hook n ladder 1 Posted April 26, 2015 Author Share Posted April 26, 2015 So just to have a few options.....if I needed to raise the front end to level off the truck, and the front springs do not need to be replaced, anybody add air bags to the front? I was looking at canadianloadshare.com. Anybody have these or a similar front axle airbag kit on their truck? Quote Link to comment Share on other sites More sharing options...
Timmyb Posted April 27, 2015 Share Posted April 27, 2015 I don't think they will raise it much. For instance, if a truck with good springs and good ride height used them it would make it too high. Take the truck to a wheel alignment place and get them to put packers in between the spring and axle. If you do go with the load share front air bags I would love to hear your thoughts on them as I've been thinking of trying them out. Quote Link to comment Share on other sites More sharing options...
2006Largecar Posted April 28, 2015 Share Posted April 28, 2015 Ive been working on a peterbilt that i have, for over a year now. In fact, the reason why im a mack owner as well, is because my peterbilt project has taken me quite some time, and i had to keep my customers happy. Anyway i airbagged my steer axle with a home built setup. Unfortunately, i haven't gotten it on the road yet. A bunch of my buddies have done it with alot of success, although there are a few varying opinions on the way to do it. Ive driven a few, as well as a factory setup on a kenworth 660. The kenworth has four bags with a leveling valve, where as mine is pressure controlled by me from inside the cab. (Probably similar to the setup you are looking at). In my experience, they ride well and smooth out the bridge joints. All setups that I am talking about have the bags mounted over the axle as a helper bag. A lot of guys use the airbag from the kenworth 8 bag suspension. Quote Link to comment Share on other sites More sharing options...
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