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Drive line angles


jenandjon
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My truck was singled when I got it. The previous owner simply pulled the front rear and extended the drive shaft. My camper at the time was very light but I did get a little vibration when it pulled harder running across the Rockies. I dont think anything of it. Its an old truck with 1.3 million miles on it.

Forward ahead a couple years I got a newer much larger trailer. I take off from the dealer and as I'm rowing the gears I got a vibration. I recognize it immediately as the same vibration I got in the mountains. I get up to speed, set the cruise its fine. Come to a hill and it pulls harder the vibration starts up again. So I'm thinking transmission. I call a mechanic friend of mine to see if hes got anything used laying around. I go through the whole spiel. Everything I just said above.

He asks if they changed the angle of the rear end when it was singled. Because the rear rear sits at a different angle than the front rear. You need a 12 degree pitch. He thinks when I'm pulling harder its flexing the rear end changing the drive line angle causing vibration.  I said OK I have to check that out. I didn't drain my low points in time and they froze I have to pull the camper in the shop anyway. We just happen to have one of the farm trucks in there right now so I pull up side by side and get the creeper out. Sure as I'm sitting there they are different.

So I call the guy I bought it from and asked if he changed anything. No he didn't think to change anything. So he walks over to his truck and says yea they are different angles but it never even crossed his mind that it would make a difference.

I need to get a hold of Freightliner and find out exactly what the drive line angle is suppose to be then Figure out what mine is. I dont know exactly how to do that.

I will be posting pictures below off my phone. They are not very good but if you know what you are looking at you will see there is a difference.

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27 minutes ago, jenandjon said:

I cant post pics because I got a new phone and apparently they are too big. I value my life enough not to wake Jen at this hour on a weekend to fix it. Pics will have to wait.

Put your pics on an external site, like Dropbox or Google Photos and then embed them here and it will not matter what size the pics are. In fact, Google Photos by default optimizes them for space saving.

 

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We don't really need pics, but they will help the newcomers. Get in touch with a driveline shop, have your u-joint size ready, and they will be able to tell you what angles that joint wants. The angles are measured off the face of the yoke. The reason I'm saying to get ahold of a driveline shop, instead of Freightliner, is because you don't have a stock driveshaft anymore. When the axle was removed, the shaft had to be modified by replacing the rear yoke. The yokes are different on the front axle and rear.

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Call Freightliner, buy the axle seats and u-bolts that match the angle the fwd axle used to have (2,3,4 ~ish deg).  I don't know Freightliner, but maybe the original fwd axle seats will work on a rear axle.  The axle slant needs to get to near the engine slant or it won't work out.  Set the axle, then you can do all the math (or hold/measure/adjust with a crane) and lower the centerbearing to get the perfect angles.  Or maybe with the axle set right it'll be close enough....

Shaft angles need to target a compound 3 deg, shouldn't be much over 5deg if overdrive trans.

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6 hours ago, Scrap said:

Call Freightliner, buy the axle seats and u-bolts that match the angle the fwd axle used to have (2,3,4 ~ish deg).  I don't know Freightliner, but maybe the original fwd axle seats will work on a rear axle.  The axle slant needs to get to near the engine slant or it won't work out.  Set the axle, then you can do all the math (or hold/measure/adjust with a crane) and lower the centerbearing to get the perfect angles.  Or maybe with the axle set right it'll be close enough....

Shaft angles need to target a compound 3 deg, shouldn't be much over 5deg if overdrive trans.

Ok Thanks. I will do some investigating.

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I'm going to have to replace my leveling valve lever again. Last time I did it I didn't realize how specific it was and got some vibrations. Luckily I found  a shop that noticed it and adjusted it correctly. This one is going to cost me more though. If you have ever driven many miles with it just hanging you know what I mean. Embarrassed to say I never thought it was why the road was so rough when it looked so new. Hopefully a lesson learned. If something doesn't feel right it isn't. I missed my GOAL opportunity until I was at my destination. 

Rod

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On 10/25/2020 at 8:39 AM, jenandjon said:

I cant post pics because I got a new phone and apparently they are too big. I value my life enough not to wake Jen at this hour on a weekend to fix it. Pics will have to wait.

I use http://photoposting.is-great.net/?i=2  or https://postimages.org/

Another possibility is the driveshaft is out of time = unbalanced  as a result of being taken apart, upon re-assembly the timing marks were not matched.

Edited by Ray,IN
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