Driveline vibrations

[kleake]

2008 F250, crew cab, 6.4, short bed, 4x4, stock height.

Daily driving is fine, but when towing I get major driveline vibrations through 1st gear, reduced in 2nd but still there, by 3rd all is smooth. It's always had it but seems to be getting worse. I'm towing a 36ft 5th wheel so i've got at least 2-3k lbs on the rear axle.

I removed the 1" spacer above the carrier bearing and it helped, but didn't eliminate it. I have also added shims on the rear axle to tilt the pinion lower in hopes that when under high torque it doesn't rotate as high. I've looked at the driveline angles and they look pretty darn close, but I haven't actually measured them. With no lift, I would have guessed they are pretty close already. I never feel it when i'm not towing, or if I am not on the throttle while towing but it's almost scary if I stop on a hill and have to get going again. I'll usually use 25% throttle through 1st, then maybe 40% through 2nd, then by 3rd I can go all the way if needed.

Anyone else have this? I'm almost ready to get traction bars to eliminate axle twist.

 

[sootie]

traction bars should eliminate it. Once you get the traction bars, get your driveline geometry correct again. With what you have done, its likely way out to lunch.

 

[Wizbangdoodle]

Pinion looks tight? No loosey goosey in any of the drivetrain?

You may need traction bars. I know a lot of guys around here use them because they compete in pulling. Are you using a slider hitch?

I'm in about the same boat as you except I have a long bed. I tow a 38' 5er. I have never experienced axle wrap.

 

[sootie]

Pinion looks tight? No loosey goosey in any of the drivetrain?

You may need traction bars. I know a lot of guys around here use them because they compete in pulling. Are you using a slider hitch?

I'm in about the same boat as you except I have a long bed. I tow a 38' 5er. I have never experienced axle wrap.

How do you know you have never experienced axle wrap?

The guys pulling that install traction bars do it for the very reason you need them when pulling a trailer!

 

[Wizbangdoodle]

OK, I'll say I've never experienced the vibrations the op is describing.

 

[kleake]

All feels tight, even new u-joints and carrier bearing last summer. Although, both front and rear pinion seals are starting to leak, but I couldn't feel any play in them. I'll check again though.

I'm not using a slider hitch, although I wish I was. I had to make a tight turn around and bumped my cab corner with the trailer this past weekend. Minor, but I didn't have a choice with this tight turn.

I'm not sure it's 100% axle wrap although that is part of it. The harder I am on the throttle, the worse it is, but even at say 10% throttle on level ground I can feel it. Roll on the throttle and it magnifies.

As for geometry, removing the 1" spacer above the carrier last summer definitely reduced it. Probably cut it in half... The axle shims didn't seem to effect it at all, or at least any that I could tell. When I look as the driveline empty, it looks very straight. Loaded, it appears the front half of the driveline angles down and after the carrier it's more level. Almost like the carrier needs to be raised a small amount more, but it can't.

 

[sootie]

having ujoints straight is asking for failure. using a protractor, i believe it should be 4.5* from tailshaft of trans to pinion.

 

[kleake]

Well, I can't say they are perfectly straight, but they are not obviously at an angle either. Also, I understand driveline angle, and have dealt with that on my jeep with a single shaft and no carrier. Both angles should be identical or you will have vibrations. Now with the carrier and 3 joints, it gets more tricky. Now if I understand what I have changed, and what it's doing, then I "think" i'm going the right direction. Let me see if I can explain:

If I accelerate more=more axle wrap, causing the pinion to raise. Higher pinion=more vibration. The shims lowered the pinion, so that should have reduced the effective wrap. Also, raising the carrier 1" will change the angle at both ends and effectively reduce the effect of the wrap as well, but will also change the angle at the tailshaft. This did improve it though, so it seems I was headed the right direction.

These are the two things I have done per this TSB 09-4-9: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwiHyNDu6f3OAhXkx4MKHcQVB5IQFghGMAM&url=http%3A%2F%2Fwww.powerstroke.org%2Fforum%2Fattachments%2F6-4-drivetrain-problems%2F11130d1257385850-weird-shutter-vibration-tsb-09.4.9.pdf&usg=AFQjCNFQ_c8ijOcnKR1EnaO5eI83tHPx_Q&sig2=-JVOZNYqgEhWWOldNcbEgw&bvm=bv.131783435,d.amc

 

[Wizbangdoodle]

I'm no driveline expert, but I would think no matter the angle, if you are getting movement of the pinion (up and down), you'd want to eliminate that. Traction bars seem to be the answer. If I were you, I'd put a GoPro type camera under there and get some idea of what's happening under there when you drive.

 

[kleake]

I did that empty, but not loaded. I couldn't really see any movement. I think I'll try it loaded and maybe it will tell me something more.

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[sootie]

Well, I can't say they are perfectly straight, but they are not obviously at an angle either. Also, I understand driveline angle, and have dealt with that on my jeep with a single shaft and no carrier. Both angles should be identical or you will have vibrations. Now with the carrier and 3 joints, it gets more tricky. Now if I understand what I have changed, and what it's doing, then I "think" i'm going the right direction. Let me see if I can explain:

If I accelerate more=more axle wrap, causing the pinion to raise. Higher pinion=more vibration. The shims lowered the pinion, so that should have reduced the effective wrap. Also, raising the carrier 1" will change the angle at both ends and effectively reduce the effect of the wrap as well, but will also change the angle at the tailshaft. This did improve it though, so it seems I was headed the right direction.

These are the two things I have done per this TSB 09-4-9: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwiHyNDu6f3OAhXkx4MKHcQVB5IQFghGMAM&url=http%3A%2F%2Fwww.powerstroke.org%2Fforum%2Fattachments%2F6-4-drivetrain-problems%2F11130d1257385850-weird-shutter-vibration-tsb-09.4.9.pdf&usg=AFQjCNFQ_c8ijOcnKR1EnaO5eI83tHPx_Q&sig2=-JVOZNYqgEhWWOldNcbEgw&bvm=bv.131783435,d.amc

none of what you did, had any affect on axle wrap. mask it-yes. change or improve-no. axle wrap is from the lef springs twisting into an "s" shape. no amount of driveline angle changes will stop that.

 

[kleake]

I definitely agree, but my concern is why should I need traction bars to prevent axle wrap on a stock height F250 when towing? Isn't that what it was made to do? Isn't that what most of us do? So why am I having it when most others don't? Or should I say, why is mine vibrating so bad when others dont? What is different on mine? Those are my biggest questions. I know traction bars will fix axle wrap, but I would prefer to fix the underlying issue first and resort to traction bars for more of an "upgrade". I should be able to minimize the vibration to an acceptable level before resorting to traction bars.

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[sootie]

I know what you mean...my truck is lower than stock and has it. They softened up the leafs in the 2011+ trucks and when you throw a tune in, that is just enough extra power to make it noticeable.

 

[kleake]

Yep. If mine was just noticeable, I would be ok. Mine shakes everything if I am more than about 25% throttle from a stop when loaded. Extra power doesn't really come into play at that point I wouldn't think.

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[sootie]

Check your centering pins in your leaf pack to make sure they aren't broken. Also look for cracked leafs. Did you get the correct torque on the u-bolts?

 

[kleake]

Centering pins were fine when I added the shims a while back, but I'm tempted to pull them out and test again. And yes, torqued the ubolts, probably more than needed and retorqued a few days later too. No broken leafs that I can see.

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[kleake]

I put the gopro under there watching the pinion angle change as i throttle it. I really didn't observe all that much movement. Sure, there was some, and if I really got on the throttle it torqued up pretty good, but I could feel the vibes even under very little throttle. Pulling out of our campsite it was a pretty steep climb and really slow speed and I could feel it 'thump, thump, thump' as I was barely moving so I think the vibration may be coming from the carrier bearing area as it can't hold the shaft straight. I'm going to reposition the camera and watch that spot.

I can see that my clearance between the exhaust over the pumpkin and the axle is pretty tight though. On a few really good bumps they actually hit leaving only some rub marks, but nothing dented. I'm wondering if air bags would be more beneficial than traction bars? It would help with the ride, help keep the driveshaft angle under control, and level out the truck. Thoughts on which one I should try first?

 

[BS Hauler]

You are assuming that all your components are too factory specs. They might not be. I would suspect a drive shaft that is not true. At slow speed you are getting a wobble.

 

[kleake]

You are assuming that all your components are too factory specs. They might not be. I would suspect a drive shaft that is not true. At slow speed you are getting a wobble.

I thought about that, but when I first noticed the issue, I took the driveshaft to a local driveline shop and had them put in new u-joints, carrier bearing, and balanced it. All checked out good, but it didn't effect the vibrations at all.

 

[Big Bad 6.4]

Have you checked your ring and pinion gears? Maybe something's a little off in there? Traction bars really help a lot towing or not, especially with a tuned truck.


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