Prostar bouncing/shaking when empty

[GhostHauling]

Steering wheeling very lightly pulls to the right at times nothing crazy and loaded with anything over 10k lightest load I’ve had and up to 49k truck rides smooth as can be at all speeds and when my truck is empty or bobtail anything over 60mph truck gets a violent bounce every few min and it gets worse as speeds increase and seems to go away when hitting bumps in the roads. I can’t find anything obvious and so far two shops can’t either. This is really annoying and it seems as the more I dead head the worse it gets

[Chamberpains]

Check your steer tire mounting, brake drum mounting and if you run equal or anything in the tire for dynamic balancing make sure its not clumping. I've had two occasions within the last year that my steer tires bounced and shook at those speeds and with the exact symptoms you describe.

The remedy that worked beautifully each time was take the steer tires off. Check runout, proper tire to rim mounting, spin balance and the most critical step... using proper stud centering pins to mount the drum and rim correctly.

Its a cheap easy check.

[SquareOne]

Yep, like Chamber said....my steers were smooth up until the 60-70k mark when one began to showed the it's issue. Started very slight, but it began nonetheless and only progressively got worse. Currently with just over 125k on them, they have their good and bad moments on the highway.... similar to what you're dealing with now.

---while you're at it, throw a pair of shocks on with the new steers as well. Cheap insurance to keep the wheels meeting the road when you put new rubber.

[DVT873]

Probably tires but assuming it is air ride check your ride height with the trailer on. Both empty and loaded. Have seen the valve loose sensitivity. Never reacts to change in load. Among other things that can cause caster to be off spec. Which can do weird things. But probably tires. Balance sleeves are always a good idea.

[GhostHauling]

Thank you guys I appreciate the advice, I’m going to get new steers and shocks since it’s winter and my steers are at about 7 on the tread but I’ll give an update if that solves it, ride height is interesting I’ll have to check. What should the ride height be ? I pull a 48’ flatbed? Btw so I’ve been finding so many different answers for tire PSI and I’ve been running 110 cold in steers and 90psi cold in drives and trailer ( I religiously check all tire psi) my drives say max cold 120 my steers say the same some trailer tires say 120 others 105. I had a trailer tire at 60 PSI and aired it up to 105 psi and it blew out an hour later. So trying to find the magic number has been an interest but after airing up my steers to 115 cold and then Dead heading the shaking seemed to almost entirely go away.

[Waterloo]

(12-05-2020 )GhostHauling Wrote:  Thank you guys I appreciate the advice, I’m going to get new steers and shocks since it’s winter and my steers are at about 7 on the tread but I’ll give an update if that solves it, ride height is interesting I’ll have to check. What should the ride height be ? I pull a 48’ flatbed? Btw so I’ve been finding so many different answers for tire PSI and I’ve been running 110 cold in steers and 90psi cold in drives and trailer ( I religiously check all tire psi) my drives say max cold 120 my steers say the same some trailer tires say 120 others 105. I had a trailer tire at 60 PSI and aired it up to 105 psi and it blew out an hour later. So trying to find the magic number has been an interest but after airing up my steers to 115 cold and then Dead heading the shaking seemed to almost entirely go away.

If you air it up that high, and it rides better, I bet you have a tire issue, like a separated belt or the tire is out of round. I just went through this with my ProStar, the steering wheel was like a jackhammer over 63 mph, a new set of tires cured it.

I run my steer tires at 110, drives at 100. She now rides like a Cadillac with all new drives and now steer tires. I went with the Michelins up front, Dayton D610D Smart Way in the rear. Fuel mileage is getting better.

[GhostHauling]

Thank you Waterloo, I’m hopeful your right, we will see probably next week When I get new steers I’ll post an update, and today I pulled off the crankcase filter to have a look see they put a maintenance free one in there it looked good a little bit of oil which I think is normal but than I pulled off my oil fill cap to check for blowby as normal and it had white gelly type liquid in the top of the cap I got worried Wiped it clean and checked oil it looked good one Letter lower from oil change 10,000 miles ago and I ran it short run and no white residue returned any idea what the hell the white stuff was ?

[Waterloo]

More than likely condensation. If it was coolant, more than likely it would have been in the crankcase filter area too. Keep an eye on it, but right now, nothing to worry about.

[GhostHauling]

I appreciate it, and I dove into the past reading the posts on the condensation issue, so I’ll keep an eye on it. So many horror stories like the fuel pump saga after reading that I was about to order a new fuel pump lol but seriously I’m gonna get a new one considering there’s 658k on it