Question For Mackpro68

[cxn613]

I had posted last week about our deal with the vibration on our cxu and nobody had replied. I guess my biggest question i'd like answered is, how do you know if your air bags are to full of air? Can taking some air out soften up the ride some without throwing the drive shaft off angle? Thank you very much for any info

[RowdyRebel]

I had posted last week about our deal with the vibration on our cxu and nobody had replied. I guess my biggest question i'd like answered is, how do you know if your air bags are to full of air? Can taking some air out soften up the ride some without throwing the drive shaft off angle? Thank you very much for any info

Adding air to the bags will raise the ride height, and removing air will lower the ride height. The air pressure will remain constant, though. You won't be able to add or remove air from the bags without throwing off your ride height adjustment.

I'm sure someone around here can help you get the ride height measurement to make sure it is set correctly...where to measure and what the measurement should be...I checked mine, but measurements might be different on yours...and I'm no pro, so I got no way to look it up for you.

[Mackpro]

I had posted last week about our deal with the vibration on our cxu and nobody had replied. I guess my biggest question i'd like answered is, how do you know if your air bags are to full of air? Can taking some air out soften up the ride some without throwing the drive shaft off angle? Thank you very much for any info

I wouldnt adjust the ride height unless you had the exact ride height measurment availible. There are at least 3 different height settings for the rear air bag height depending on the type of air ride. Its so confusing we have a service bulletin next all the different guages that we have for measuring ride height. On the CXU and CHU you dont shorten or lenghten the rod on the valve, you actually loosen the bracket on the frame that the valve sets on and you rotate it one way or the other to adjust it. Too much up or down and it will cause vibration and even possible tear the syncro out of the transmission. Eaton Fuller likes to deny warranty for syncro damage, they claim they can tell if it was caused by improper ride height. Your new CXU should have come with a Maintance and Lube manual, in it it tells some on the ride height adjustment. I will try and find the service bulletin and post it here. Also the cab air bags have a measurment too, I will see if I can find it. We had 3 or 4 CXU's and CHU's with the vibrations when new and we installed the new motor mounts, cab mounts and rear shocks. The new rear shocks were alot stiffer than the ones that came on the truck. I always wondered if when the shocks started to wear out , would the vibration return. When the CXU and CHU first came out we still had "Mack" engineers in Allentown, I was talking to one about the vibration and he said it actually wasn't the engine vibrateing, it was a sound wave put off by the engine under a certain load, the cab was absorbing the sound wave and causing the felt vibration, kinda like when your in your car at a stop light and the guy next to you has a loud sterio with giant subwoofers cranked up and you can feel it in your car.

[Mackpro]

Found the Email from Mack about the vibration============== I received your voicemail regarding the CHU613_1219 unit with the vibration complaint. Jim Gallagher is correct we have seen this issue before in which there is a reoccurring resonant vibration in the cab while under a load in mid to high range gears (at approx. 40-60mph). Here is a parts list that you will need based on a 300mm frame and “AL” suspension (see below). If you have any questions – let me know.

Rear Suspension AL461 – AL401

300mm Frame

Part Number Qty

Front Cab Mounts 30QS4590M 2

Shelf Bracket L.H - 300 30QS4617M 1

Shelf Bracket R.H - 300 30QS4617M2 1

Upper Frame Tie - 300 30QS4619M 1

Upper frame Tie Bolts 27AM16 4

Upper Frame Tie Nuts 191AM4 4

Rear Engine Mounts 20QL414M 1

Front Drive Axle Seats N/A N/A

Rear Drive Axle seats N/A N/A

Edge Shocks 4000-60675001 4

Upper Sleeve N/A N/A

Upper Sleeve N/A N/A

Lower Sleeve N/A N/A

Thanks,

- Adrian

[Mackpro]

Also found this Email responce from Mack on the issue========= These parts are for CHUs chassis that may be experience a reoccurring resonant vibration in the cab while under load in mid to high-range gears. Typically the vibration is most prevalent at highway speeds (40-60 mph) when the chassis has to negotiate a grade or when full engine power is required. The reoccurring resonant vibration will occur in the cab and in some cases may shake the dash. The cab can be isolated from the engine vibration frequencies by the installing the following parts. See attached document "CHU_VibrationComplaint Resolution".

[Mackpro]

Mack service bulletin on ride height. give me the last 6 of the vin and I can look it up and see what rear suspension you have and get you a better anwser on ride height.

sb136012.pdf

[cxn613]

Mack service bulletin on ride height. give me the last 6 of the vin and I can look it up and see what rear suspension you have and get you a better anwser on ride height.

last 6 of vin 002691

[Mackpro]

last 6 of vin 002691

Ok , your truck has the Maxilite rear suspension. With the truck on level ground, unloaded and no trailer. Release the parking brakes, dump the air bags with the switch, after they have deflated all the way, flip the switch and air them back up. Chock the front wheels. On the front rear drive axle on the LH side. Measure from the top of the axle housing to the top of the frame mounted axle bump stop. It should be 8 1/2 inches. Look at page 3 of the service bulletin and enlarge the pic of the ride height guage and you can see where you are to measure from.

[paul 111]

I had posted last week about our deal with the vibration on our cxu and nobody had replied. I guess my biggest question i'd like answered is, how do you know if your air bags are to full of air? Can taking some air out soften up the ride some without throwing the drive shaft off angle? Thank you very much for any info

[paul 111]

You can lower or raise the bags by adjusting the rod on the air bag control valve, you can lower or raise the bags as long as the slip yoke spline is not exposed, check the balance weights on tail shaft, unis and pinions for movement,could also be a faulty or worn innertube in tail shaft and as for bags being full the truck should sit level

[Mackpro]

You can lower or raise the bags by adjusting the rod on the air bag control valve, you can lower or raise the bags as long as the slip yoke spline is not exposed, check the balance weights on tail shaft, unis and pinions for movement,could also be a faulty or worn innertube in tail shaft and as for bags being full the truck should sit level

On his CXU the rod is fixed and you have to actually move the bracket that the air valve is attached to in order to raise or lower it level. I have read and seen damage due to air bags set to high or to low. I only set it the way it come from the factory. Driver's were tearin up so many transmissions, drive lines and rear axles by driving with the air bags down, now all Macks after around 2004 with air ride rears have parameters in the VECU to limit road speed to 15 MPH if the driver tries to drive with the air bags down. While these parameters can be turned off or adjusted Mack just got tired of payin warranty claims for low air bag damage. Faulty air leveling valves can do some weird stuff, had one the other day just randomly start airing all the way up while going down the road. We replaced alot of them on the new trucks.

[cxn613]

On his CXU the rod is fixed and you have to actually move the bracket that the air valve is attached to in order to raise or lower it level. I have read and seen damage due to air bags set to high or to low. I only set it the way it come from the factory. Driver's were tearin up so many transmissions, drive lines and rear axles by driving with the air bags down, now all Macks after around 2004 with air ride rears have parameters in the VECU to limit road speed to 15 MPH if the driver tries to drive with the air bags down. While these parameters can be turned off or adjusted Mack just got tired of payin warranty claims for low air bag damage. Faulty air leveling valves can do some weird stuff, had one the other day just randomly start airing all the way up while going down the road. We replaced alot of them on the new trucks.

MackPro68 what air susp. do you recomend being the best you can get on a mack?

[hatcity]

Not to derail. my truck sits heavy to the rear. Can I adjust the rear to level truck? or does it fill all bags the same?

[Mackpro]

MackPro68 what air susp. do you recomend being the best you can get on a mack?

The Max-lite you have on that CXU seem to be the most trouble-free but time will tell. To me they all are good. You can still get the Mack AL and AL2 on new trucks. It has been around the longest but is heavier and have seen alot of issues with loose U-bolts but that was mostly due to maintenance issues and not the design.

[Mackpro]

Not to derail. my truck sits heavy to the rear. Can I adjust the rear to level truck? or does it fill all bags the same?

The one leveling valve fills all 4 bags at the same time. I have see road tractors converted to dump trucks with air bag suspensions that leaned to one side or the other when loaded. We have installed another air leveling valve on the RH side so that each side had it's own valve so the truck would sit level. But I dont recommend air suspension rears on dump trucks, real squirrly going down the road loaded. Whats your vin and I can look it up, is it the orignal rear suspension?

[hatcity]

Sorry about that pic. Have NO idea how it got there, but I don't think that rear is sitting low at all.

Regarding my truck, I was just wondering if you could adjust just the rears. I have a long overhang from the rear axle to back of truck, so thats probably why it sits like that.

Even when i have a good load and with the boom on top, yeah it leeeeans a bit.

[Mackpro]

Sorry about that pic. Have NO idea how it got there, but I don't think that rear is sitting low at all.

Regarding my truck, I was just wondering if you could adjust just the rears. I have a long overhang from the rear axle to back of truck, so thats probably why it sits like that.

Even when i have a good load and with the boom on top, yeah it leeeeans a bit.

Looks like you got a lift axle on the very back, is this correct? If so, if you crank up the air to it does it help?

[hatcity]

If i have a load on, I can feel the front bounce a bit. I do drop the axle and it settles out nice. Even so, the truck will lean a bit more.

Like I said earlier, not a big deal. Was just wondering if i could add some to the rear only.

Thanks, Ed

[Gambi80]

Sorry about that pic. Have NO idea how it got there, but I don't think that rear is sitting low at all.

Regarding my truck, I was just wondering if you could adjust just the rears. I have a long overhang from the rear axle to back of truck, so thats probably why it sits like that.

Even when i have a good load and with the boom on top, yeah it leeeeans a bit.

So long as you're not texting pictures of your genitalia and leaving nasty voice messages with that reporter like Brett Farv-eh...

[country boy]

Ok , your truck has the Maxilite rear suspension. With the truck on level ground, unloaded and no trailer. Release the parking brakes, dump the air bags with the switch, after they have deflated all the way, flip the switch and air them back up. Chock the front wheels. On the front rear drive axle on the LH side. Measure from the top of the axle housing to the top of the frame mounted axle bump stop. It should be 8 1/2 inches. Look at page 3 of the service bulletin and enlarge the pic of the ride height guage and you can see where you are to measure from.

mackpro68 can you tell me how to check wastegate on a mack 460

[cgallamore]

Not to derail. my truck sits heavy to the rear. Can I adjust the rear to level truck? or does it fill all bags the same?

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[Mackpro]

mackpro68 can you tell me how to check wastegate on a mack 460

I have a Mack Service bulletin SB214017 that tells all about the wategated turbo on the 2001 (starting in OCT) - 2003 ETECH 460 HP engines. Its a 15 page bulletin and I have it printed but cant get it in a format that I can attach here. I can fax it to you if you have a fax machine? Really you should just put no more that 40psi if air pressure to the wastegate and and it should move/open. Any more that 40 PSI and it could blow the diaphragm. If it doesnt move and you hear air leaking its a blow diaphragm. If you dont hear air leaking and it dosent move it's stuck. Soak the lever with penatrating oil and try to free up.