Pinnacle

[cxn613]

I had stated in a post sometime ago(a year or so) that right after my company that I work for took delivery of our new pinnacle it seemed to have a vibration getting up to speed. The fix for this was new shocks, cab and motor mounts, which took the vibration away, but the truck rides alot rougher now than what it did before they did this. The suspension just seems alot stiffer now, even the slightest uneven terrain will make a wheel spin, but we never noticed that untill they did this upgrade. So my question for the mack techs. is,, Are the new shocks a stiffer shock than what was on it? Could we put shocks on it that was on it to get the smooth ride back? Did the cab and motor mounts fix the vibration and the new shocks weren't really needed? I love the truck, but I would like the smooth ride back.

P.S. Why did Mack go with the shocks on the outside of frame on the pinnacles instead of the inside like our vision? The vision rides real smooth.

[Mackpro]

I had stated in a post sometime ago(a year or so) that right after my company that I work for took delivery of our new pinnacle it seemed to have a vibration getting up to speed. The fix for this was new shocks, cab and motor mounts, which took the vibration away, but the truck rides alot rougher now than what it did before they did this. The suspension just seems alot stiffer now, even the slightest uneven terrain will make a wheel spin, but we never noticed that untill they did this upgrade. So my question for the mack techs. is,, Are the new shocks a stiffer shock than what was on it? Could we put shocks on it that was on it to get the smooth ride back? Did the cab and motor mounts fix the vibration and the new shocks weren't really needed? I love the truck, but I would like the smooth ride back.

P.S. Why did Mack go with the shocks on the outside of frame on the pinnacles instead of the inside like our vision? The vision rides real smooth.

We mostly had the problems with the CHU model trucks however I have heard the the CXU truck could have it too. All the ones I heard of had MP8 engines. The Mack engineer I talked to said it was a "hamonic vibration" from the engine and the cab "soaked" it up. All of those engineers are gone from Mack now since the big move from Allentown. One small note, one of the CHU's still had a slight vibration after we installed all the new parts, it was later that we found out it had a out of balance drive shaft. Here is a E-mail from Mack back on 2/12/08. I received your voicemail regarding the CHU613 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,