73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Topic started by: Backwoodsballer on March 16, 2024, 12:14:21 PM
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Hi all, I am new to the forum. It’s rare for me to feel the need to make any posts about questions since everything has been discussed at length usually, especially pinion angles. My issue seems to be odd which is why I’m looking for some help.
My truck (1978 k10 long bed) has what I believe is a 4” suspension lift (no blocks, full leaf lift) and 3” body lift. The issue I’m having is that I believe my truck has a pinion angle that is pointed too high leading to vibration issues. From what I gather, most people don’t need angle blocks with a lift on long beds and if they do need them they are installed to point the pinion higher toward the transfer case. In order for my transfer case and my pinion to be closer matching in angles I would need to install angle blocks backwards to point in down some.
My measurements below were pulled using the Tremec driveline angle finder.
Transfer case: 2.2 degrees
Driveshaft: 13.2 degrees
Rear pinion: 9.9 degrees
Am I correct in thinking I need to install angle blocks backwards to try and get my pinion angle closer matching to the transfer case? Or would this be a candidate to drop the tcase to lessen the difference between the tcase and driveshaft? Either way, I think something is wrong here and is likely causing my highway vibration issue
Thanks everyone
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There are several factors to consider but if your feeling is that the rear pinion is up too high with a 4" lift, I would question why? Some pics would help. A body lift is going to affect linkage and cause other potential issues if dropping the transfer case. Flipping the spacers on the transfer case can help get a better driveshaft angle if necessary but I wouldn't with the body lift. Spring length, arch, hangers and shackles also change things so you need to figure out what's going on. Did the vibration just start? Are the u-joints good?
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I wish I knew more about the actual specs on the lift, the truck is newish to me. The vibration I get is only at highway speed and feels like a shake more than anything. In an attempt to try narrowing down my issue without throwing money at i, I figured I would start with taking measurements on the driveline angles.
I already put quality u joints on the rear shaft within the past month. With the measurements I took it looks to me like my rear pinion angle is pointed very high in comparison with the transfer case.
The reason I’m trying to get clear answers on this is because I’ve heard people with block lifts don’t need to add shims since it’s not really changing the geometry, but my spring lift must have changed it in a way that caused the pinion to point up
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Here are a couple pictures of how it sits now. Without a double Carson I don’t think the pinion should be so inline with the driveshaft. With the pinion measuring 9.9 degrees and the trans at 2.2 I was figuring I need to drop the nose of the pinion down to match or get close to the same angle the trans has, from what I understand that is what u joints like in order to cancel out vibration.
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If yours is a longbed does it not have a 2 piece prop? At least that would help with the prop shaft angle out of the tranny?
Graham
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Yeah it’s a long bed with a “1pc shaft”. Technically it’s 2pc but I know what you mean, I don’t have a carrier bearing on mine
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Can't really see anything from your pix. Does the vibration change if you decel or shift into neutral?
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No, the vibration remains the same on the highway during decel and remains if I shift the truck into neutral until it coasts to about 55mph where it smooths out
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Is there any unusual noise with the vibration?
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Nothing unusual, the vibration feels like it’s in and out if that makes sense. Sometimes it feels like the truck is going back and forth between the rear going up and down and side to side.
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How is the condition of the slip/yoke? does it lessen after lubing it up?
I had a worn out one on my '78.
Is there anywhere that can spin the driveshaft to check balance?
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From what I could tell it felt normal but I’m no expert. I could take it to a shop that specializes in drive shafts to have them inspect it, there is a shop not too far from my work.
I had my buddy with a square body lifted with blocks and his driveline angles are way different than mine. Primarily the trans to driveshaft working angle is about 5 degrees for him where mine is around 11 degrees
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No, the vibration remains the same on the highway during decel and remains if I shift the truck into neutral until it coasts to about 55mph where it smooths out
This is exactly the issue I am having! I recently did a 1 ton axles swap, every single thing in the axle is new/upgraded, new u joints and 2.5" soft ride springs. I haven't even checked the pinion angle yet, But did put my truck in neutral and shook the drive shaft. I found that I have play on the rear output of the transfer case. I would guess a 1/16th each direction. This seems to be a very obvious issue that would affect my drive line. I just got my other transfer case out of storage and will be addressing that shortly. But in the meantime I have a video that might be helpful to you.
Mods if this isn't allowed I'm sorry, I won't directly link it. But if you search YouTube for "Tom Woods Custom drive shaft channel" video entitled " diagnosing drive shaft vibrations" it was very helpful.
Please when you find the solution please let us know for future members searching, I will do the same!
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FWIW
Gear Vendors (in my neck of the woods) states that 6 degrees is the right mark.
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I might try to install my wedges and see if that makes any difference. I have 6 degree wedges at home now, ill install them backwards so the pinion will roll down making it alot closer to the angle the transmission has.
I was hoping someone else on here ran into this before but it doesnt seem to be all that common
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I'd say from your third picture it doesn't look like you have any angle on that rear u-joint. U-joints need to have a little angle on them to keep the needle bearings spinning; at least 1° If not, the U-joint life will be severely reduced. From you numbers I would say you want an 8° shim to angle your rear-end down to like 1.9°. Typically with leaf-springs you will go a little past equal angle between the transfer-case and the rear-end. If your powertrain is angled at 2.2° then you would want your rear-end angled at almost 0°. This is because when you put torque to the rear-end the pinion wants to climb the ring-gear and the leaf springs will flex in an S-shape, called spring wrap, letting the yoke rotate up.
The problem with U-joints and lifts is that a U-joint has a practical limit for a working angle. Typically this is going to be around 15°. They can go steeper angles, but even by 15° the U-joint life is drastically reduced. For you your working angle at the transfer-case is 11° and your working angle at the Rear-end is 3.3°, assuming your measurements are accurate. If you put in an 8° shim then your working angle at the rear-end will be about 11.9° and your working angle at the transfer-case will be about 11.6°. Your driveshaft will lengthen slightly, so you want to be sure that you have proper engagement of the slip-yoke. Depending on your engagement now at the slip-yoke, it might have to be lengthened. I think you want to be sure you have at least 2 inches of engagement. That could be another source of vibration.
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BTW...on my 8" lift in my crew-cab I have a two piece driveshaft. The carrier bearing is spaced down slightly to improve angles. I had a very bad vibration in it when I bought it. The problem was, 1) not enough engagement in the slip-yoke because of the lift, and 2) the 2-piece of the shaft was bent, only 0.150". I had it lengthened...i.e. re-tubed and the slip-yoke replaced (it was worn-out from not enough engagement), and the vibration totally went away.
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I'd say from your third picture it doesn't look like you have any angle on that rear u-joint. U-joints need to have a little angle on them to keep the needle bearings spinning; at least 1° If not, the U-joint life will be severely reduced. From you numbers I would say you want an 8° shim to angle your rear-end down to like 1.9°. Typically with leaf-springs you will go a little past equal angle between the transfer-case and the rear-end. If your powertrain is angled at 2.2° then you would want your rear-end angled at almost 0°. This is because when you put torque to the rear-end the pinion wants to climb the ring-gear and the leaf springs will flex in an S-shape, called spring wrap, letting the yoke rotate up.
The problem with U-joints and lifts is that a U-joint has a practical limit for a working angle. Typically this is going to be around 15°. They can go steeper angles, but even by 15° the U-joint life is drastically reduced. For you your working angle at the transfer-case is 11° and your working angle at the Rear-end is 3.3°, assuming your measurements are accurate. If you put in an 8° shim then your working angle at the rear-end will be about 11.9° and your working angle at the transfer-case will be about 11.6°. Your driveshaft will lengthen slightly, so you want to be sure that you have proper engagement of the slip-yoke. Depending on your engagement now at the slip-yoke, it might have to be lengthened. I think you want to be sure you have at least 2 inches of engagement. That could be another source of vibration.
Thank you so much for this, this was exactly what i was looking to clarify here. I had the same understanding that i need to get the pinion to point down more to be more-so on the same plane as the trans. Ill work on shimming my rear axle this week and report back.
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There are aluminum shims and steel shims. Some have a clearance hole for the spring center pin, some bolt to the spring pack. I suggest getting the steel shim that bolts to the spring pack. You may need a new, longer center pin for your spring pack. The most important thing is that the Center Pin engages the hole in the axle pad so that your axle does not shift on the leaf spring.
Something like this: https://www.wfoconcepts.com/i-30504779-8-degree-steel-axle-shim-2-5-wide.html
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My measurements below were pulled using the Tremec driveline angle finder.
Transfer case: 2.2 degrees
Driveshaft: 13.2 degrees
Rear pinion: 9.9 degrees
can you confirm that you measured off the flat surface and got 2.2 Degrees DOWN on the T-case output and 9.9 degrees UP on the Ujoint face of the axle?
Ideally you want them both to be in the same plane if the T-case is pointed down 3 degrees the axle should be 3 degrees up. If what you are posting is what I stated above you are 7.7 degrees off.
check this link out..
https://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Single-Cardan-Measurements
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Yes I can confirm all measurements were made on flat spots on the transmission and rear axle.
Thank you for helping clarify, I think this thread will help a lot of people in the future just to understand what we are looking for
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Just wanted to update, I put in the 6 degree wedges I had here on the truck tonight and it brought the pinion angle down to a reasonable 3.3 degrees. I’ll try to take it for a ride tomorrow, hopefully this helps my issue.
Also I noticed that the hole in the axle where the leaf spring retainer bolt goes in was totally wallowed out, it honestly looked like the axle might have been shifting back and forth in the hole so much that it almost made a slot. I made a spacer to put in the hole and welded it up, it was literally the size of another bolt head.
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Increasing the angle of your pinion to it is more out of line with your driveshafts seems to be going in the opposite direction, i.e. adding more work/movement to your rear U joint.
I think the problem is either 11 degrees is too much, or your slip joint yoke is worn.
If you can move it sideways or up and down, I suspect it's worn and wobbling. When I would grease mine up it smoothed out till the grease worked out.
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I did check the slip joint on the driveshaft and i seemed to be tight, i did grease it within the past 2 weeks as well. There is not really any movement at all in the drive shaft when i get under there and twist / shake it, then again im sure it doesnt take much movement to cause a vibration so i might be missing something.
Matching the pinion to the trans in theory should allow the rear u-joint to cancel out the vibration from the front u-joint however this working angle will definitly cause my u joints to wear down more. Im hoping the test drive proves this to be correct.
I think the only real fix for me with this amount lift / driveshaft angle is to get myself a double cardon driveshaft or a CV end on the transmission side then setup my pinion angle to point at the transmission. There is no slip yolk for my transmission now, my driveshaft bolts directly to the output shaft by the u joint.
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Well I took it for a ride yesterday and today. To me I think the vibration is worse. It’s not vibrating around 40mph and anytime I’m on the throttle, which it was not doing that before. I really thought getting the pinion angle and transmission on the same plane was going to fix it but oddly enough it made it worse. On top of that it looks like I would need a longer driveshaft to keep it this way anyways.
I think I’ll be taking out the wedges and putting it back to the factory setup. I’ll have to chase my wheels next for this vibration issue I was getting at highway speeds
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Makes sense, I would still have the balance checked to rule out the drive shaft.
I think there is a CV or double U-joint coming off the Xfer case going to the front axle on my K10. It a pretty sharp angle being so close to the front.
Just thinking out loud: from a geometry POV, angling the pinion downward increased the angle at the transmission U-joint.
Keep us posted on what you find, happy hunting!
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Can you take it to a shop where you can run it in place at speed while observing under the vehicle for problems?
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Yeah i certainly could try that out to see what might be vibrating. Even seeing if the driveshaft is running true would be worth that exercise i think. One thing i did notice last night when i went back out there was that the slip joint in the driveshaft seemed to have some slop (like JohnnyPopper mentioned earlier). There is not slop that i could feel by hand when twisting it, but there is slop when i push up and pull down on the shaft. Maybe this is exaggerated since my driveshaft is stretched to the max right now but it doesnt seem normal to me.
I was also looking into just picking up a double cardon shaft from Tom Woods for the rear and pointing the pinion up to the Tcase, but thats a hefty chunk of change for a potential fix.
I had my buddy check his angles on his 80's K10 long bed with a 4" block lift in the rear and they are much closer to my original measurements, his truck drives smooth as silk:
His Truck:
-Trans 5 degrees
-DriveShaft 8 degrees
-Pinion 10 degrees
My Truck (Original Measurements):
-Trans 2.2 degrees
-DriveShaft 13.2 degrees
-Pinion 9.9 degrees
My Truck (New Measurements):
-Trans 2.2 degrees
-DriveShaft 14.0 degrees
-Pinion 3.7 degrees
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One question...are your U-Joints still properly phased, front to back? They should be lined-up so that the yokes on both ends of the driveshafts are aligned. See the pictures and explanations located here: https://managedmobile.com/driveshaft-phasing-importance/
If you took apart your slip joint and didn't keep them properly aligned, this could be a source of vibration.
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Thanks ehjorten, My U joints are in phase properly. I actually look the driveshaft out and laid it on my garage floor on sockets to make sure it was perfect before putting it back in.
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Push up / Pull down slop is what mine had before I replaced it.
There should be no movement.
Vibration is now gone.
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Awesome, thanks JohnnyPopper. I think we are starting to narrow this down.
Ill call into to Tom Woods today and see if they think i should stick with the conventional shaft (OEM) with a single joint on either end or if i should just move up to a double cardon joint.
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I would drop the transfer case first. It will more than likely take care of it.
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Just wanted to post up my findings after installing the Tom Woods Double Cardan Shaft. The vibrations are definitely less now with a proper shaft and proper angles for the double cardan. The remaining vibration im having are likely related to the wheels i have so ill be taking them to be balanced soon. I ran the truck up to 72mph yesterday, and the only vibration i felt was one that seemed to be tire related.
Thank you all for your help!!
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Happy ending! Love it!