Help me diagnose a driveline vibration - Slinky 3" lift (1 Viewer)

[digitalmarker]

with a lathe they made

What is a lathe? Like a spacer?

 

[digitalmarker]

Ok guys, here is some more troubleshooting I've done today that I am not sure what to do with.

Today I removed the rear drive shaft. I then drove the truck with the center diff locked, with both drive shafts - the single DC and the double DC one.

They both produced different types of vibrations, similar to what they have produced in the past.

However, the single DC shaft vibration got noticeably worse when I put the rear drive shaft back in.

I have tested the rear drive shaft WITHOUT a front drive shaft, and it produces no vibrations - drives perfectly smooth.

But a combination of a rear drive shaft and front drive shaft produces significantly more vibration.

Does this mean it could be a transfer case issue?

 

[digitalmarker]

And this keeps getting weirder.

Tonight I reinstalled the double-double CV shaft.

I tried both out of phase, and then back to the in-phase angle as it was before.

The vibration actually got significantly worse... it shakes now almost the same way the single CV driveshaft does.

So I am starting to suspect it’s something other than just an angle but tried to move around everything I could and everything seems tight and solid.

I had several people mention that there is a way to slightly drop the transmission and transfer case, which would improve the front diff to TC angle. Right now my front pinion angle is 6.4*, and the driveshaft angle is 10.4*, leaving the difference of 4* - 1* higher than is considered an acceptable threshold.

Any links or info on this method? Can’t find anything about a spacer kit to lower the trans or TC.

 

[landtank]

I’d put the stock arms back on with the front stock drive shafts. Basically bring things back to square one with the exception of the lift.

And make sure the axles are centered on the truck.

I would expect the truck not to vibrate at this point.

 

[BILT4ME]

And this keeps getting weirder.

Tonight I reinstalled the double-double CV shaft.

I tried both out of phase, and then back to the in-phase angle as it was before.

The vibration actually got significantly worse... it shakes now almost the same way the single CV driveshaft does.

So I am starting to suspect it’s something other than just an angle but tried to move around everything I could and everything seems tight and solid.

I had several people mention that there is a way to slightly drop the transmission and transfer case, which would improve the front diff to TC angle. Right now my front pinion angle is 6.4*, and the driveshaft angle is 10.4*, leaving the difference of 4* - 1* higher than is considered an acceptable threshold.

Any links or info on this method? Can’t find anything about a spacer kit to lower the trans or TC.

Since the TC is married to the trans and the trans is married to the engine, you cannot "lower" the TC to get a better drive line angle unless you lower the engine mounts as well. Otherwise, you will be changing the angle of the engine/trans/TC in the frame and that will actually make your front DS angle more, not less.

There are many on here with 6"+ lifts that don't appear to have these issues any longer.

Search out their combinations, then follow along their line if thinking.

Or take it back to the 2.5"-3" lift to get back to the no vibe zone. Anytime one is above this, driveline vibes get harder to find and more expensive to fix.

 

[baldilocks]

There is a solution that would allow you to keep your suspension as is but it involves a cut and turn of the knuckles in order to retain castor angle after cutting the radius arm brackets free of the axle housing and rotating the pinion up to where it needs to be and welding the arm brackets back on.

IIRC, you are reluctant to go part time because you need smooth AWD performance for winter trips to Tahoe. I’d toss the double DC shaft inTo the corner and stick with the known which is the single dc.

My rig measure 25.25” from font hub to fender, I run Delta 6” arms and a single DC shaft. My pinion the driveline relationship is similar to yours and, with hubs and CDL locker, I can travel about 40-45mph before vibes become concerning. 40-45 mph seems fast enough in a situation where AWD/4WD is actually required on maintained roads. In this case you could go part time and be happy. Or you can lower the lift as suggested earlier today, or you can try a set of 2” Delta arms but then castor angle would suffer unless you also went with shorter springs, or you could get out the torch and welder.

Spacing the trans crossmember down will relieve rear driveline angle, worsen front driveline angle especially at the front TC output and possibly cause a number of other problems in the engine bay.

 

[n0rth]

I'm running the Slinky kit @ 4" with front Stock control arms, stock front driveline and Slee caster plates rear is adjustable Blackhawk UCA and Blackhawk LCA with adjustable track bars front and rear. I had a vibration similiar to yours and traced it to my Creeper Sleeper skid plate/crossmember. After installing the skid/crossmember with my old suspension (OME) I had to adjust a few times to get rid of a vibration/growl. I then had to adjust it again when I switched to the slinky set up it caused the vibration/growl come back.

 

[digitalmarker]

I'm running the Slinky kit @ 4" with front Stock control arms, stock front driveline and Slee caster plates rear is adjustable Blackhawk UCA and Blackhawk LCA with adjustable track bars front and rear. I had a vibration similiar to yours and traced it to my Creeper Sleeper skid plate/crossmember. After installing the skid/crossmember with my old suspension (OME) I had to adjust a few times to get rid of a vibration/growl. I then had to adjust it again when I switched to the slinky set up it caused the vibration/growl come back.

What did you adjust exactly and how?

 

[digitalmarker]

@baldilocks @BILT4ME so the idea of lowering the gearbox came from Darren McRae, a LC builder out of Australia.

He suggested adding a 1/4” spacer between the cross member and where it mounts to the frame. He said it would slightly change the angle by lowering the gearbox and that this is how he has dealt with vibrations like mine that wouldn’t go away via other means. This is a pic he sent me (of my rig) where the spacer would go.

I am not 100% sure how this would help, but he seems to think it might work.

I definitely don’t want to do a cut and turn approach. What bugs me is that there are a ton of guys on here with way bigger lifts than mine, running similar setups in terms of radius arms etc, who have no vibration issues.

This makes me question whether my issue is caused by the pinion angle or whether it’s something else.

 

[baldilocks]

Everyone has a different tolerance for noises and vibration. What one guy finds acceptable might be unacceptable to you. I’ve seen a couple rigs with Slee 6” lifts and arms and the pinion angle on both was farther off than yours. This tells me some people tell tall tales.....

So, just today I went up on the local mountain and on my way home I decided to lock the CDL, but not the hubs, and I was able to drive 55 spinning the front driveline, but not loading it, and there was no disconcerting vibration noted. Not sure if it would be worse with the hubs locked. I didn’t have a chance to go any faster than 55.

Are you positive that the front shaft is balanced and in good mechanical order?

If Darren has done the trans mount drop method with success, it might be worth a try.

This is a shot of my front pinion/driveline angle for refernce:

 

[landtank]

Vibrations come from the rotational speed difference from u- joints running at different angles and fighting each other. Having the hubs unlocked eliminates the fighting and only indicates the shaft is balanced.

But from that picture I’d bet you would feel some vibrations.

 

[n0rth]

@baldilocks @BILT4ME so the idea of lowering the gearbox came from Darren McRae, a LC builder out of Australia.

He suggested adding a 1/4” spacer between the cross member and where it mounts to the frame. He said it would slightly change the angle by lowering the gearbox and that this is how he has dealt with vibrations like mine that wouldn’t go away via other means. This is a pic he sent me (of my rig) where the spacer would go.

View attachment 2331470

I am not 100% sure how this would help, but he seems to think it might work.

I definitely don’t want to do a cut and turn approach. What bugs me is that there are a ton of guys on here with way bigger lifts than mine, running similar setups in terms of radius arms etc, who have no vibration issues.

This makes me question whether my issue is caused by the pinion angle or whether it’s something else.

The Creeper Sleeper skid/crossmember mounts the same as the bolts circled in the photo and are slotted to give side to side and a little front to back movement I can't remember if the stock one is slotted. When I originally installed the CS skid I supported the Trans/TC with my floor jack and pulled a bonehead move releasing the jack letting the trans/TC drop with no crossmember putting everything out of whack, front tranfers case yolk was pointing up even the motor mounts looked stressed. I initially just jacked it up put the skid/crossmember on and drove it, that's when I noticed the vibration/growl. I went back and supported the Trans/TC with a floorjack loosened the 4 crossmember bolts then shake/shimmy the floor jack to adjust the TC side to side in the slots which made my vibe/growl go away. After installing the slinky suspension and ditching the OME stuff the same vibe/growl came back. I tried the process and it worked again for me, what Darren suggested made me think it was worth bringing up.

 

[Box Rocket]

Couple more thoughts. First of all, I'm not sure you're really at 4" of lift. The 20" hub to fender stock measurement not consistent. I've found several examples of stock height trucks at 21" and even a couple at almost 22". Of course there are some lower than 20" too. In addition, I went back to look at my notes from when I first installed my Slinky stage 1 kit. I installed it with Darren McRae looking over my shoulder. We confirmed my truck at stock height was 21" and the lift came out right at 3". My hub to fender measurements were the same as what you have, 24". So, you may believe you have 4" of lift, but that's debatable. Sounds to me you are right about where you should be for lift height with a 3" Slinky kit. That's not critical information but I wouldn't let the lift height concern you too much.

I went back to read earlier posts and didn't see anything about the ujoint/pinion angle at the rear diff. I would confirm that your angles are correct with the rear DS flanges (as you know, should be parallel). It's entirely possible that vibration from the rear DS could be felt farther forward in the drivetrain. With the front shaft removed and no perceived vibration from the rear shaft with just the rear in place, might not guarantee that there's no vibration in the rear. It just might not be noticeable without the load of the front shaft in place. When that front is loaded, rear vibration could be intensified. If I were betting money, I wouldn't bet that this is your problem, but it's still a possibility. So I'd double check for slop in the rear u-joints and slip joint and that the shaft is in phase and flanges are parallel ( if not parallel consider longer lowers or adjustable uppers to correct pinion) . If possible, check the rear shaft for balance as well.

I agree with @landtank, I would remove the Delta arms and put stock arms and caster plates in and see the result. That would be identical to my setup that has zero vibrations. There are several others with this same setup also that don't have vibrations. If you still feel vibes, I'd pull the stock arms and plates and put your Slee arms back in and see the results. If one of the setups doesn't have vibes I'd stick with those arms.

It's tricky because you changed several things at the same time so it's difficult to isolate what change is causing the issue. It's still possible that it could be an issue in the front end even though the parts are fresh.

You've ruled out anything with the tires, correct?

 

[azngarage]

He suggested adding a 1/4” spacer between the cross member and where it mounts to the frame. He said it would slightly change the angle by lowering the gearbox and that this is how he has dealt with vibrations like mine that wouldn’t go away via other means. This is a pic he sent me (of my rig) where the spacer would go.

I have the IPOR Skid Plate and it's lower the transfer case 1/4 inch.

 

[tacocat]

I agree with @landtank, I would remove the Delta arms and put stock arms and caster plates in and see the result. That would be identical to my setup that has zero vibrations. There are several others with this same setup also that don't have vibrations. If you still feel vibes, I'd pull the stock arms and plates and put your Slee arms back in and see the results. If one of the setups doesn't have vibes I'd stick with those arms.

It's tricky because you changed several things at the same time so it's difficult to isolate what change is causing the issue. It's still possible that it could be an issue in the front end even though the parts are fresh.

You've ruled out anything with the tires, correct?

In order to go with Caster Plates, OP would have to trim and drill the axle control arm mounts, weld them in, and drill back through the new caster plates when they decide to go back to aftermarket arms.

You can drive the truck with stock arms and stock caster settings with the lift. Be aware that steering will be twitchy, but it should be acceptable for short term experimentation on empty roads.

 

[Box Rocket]

In order to go with Caster Plates, OP would have to trim and drill the axle control arm mounts, weld them in, and drill back through the new caster plates when they decide to go back to aftermarket arms.

You can drive the truck with stock arms and stock caster settings with the lift. Be aware that steering will be twitchy, but it should be acceptable for short term experimentation on empty roads.

My suggestion for stock arms and caster plates was with the assumption that the OP's truck was set up with them at some point. Caster plates can be installed without welding the plates in. So wouldn't need to be nearly as invasive as you described.

 

[tacocat]

Perhaps, but the caster plates would not return the pinion angle and transfer case angle back to stock specs, correct?

Without the caster plates, the pinion and transfer case angles should be at factory specs in relation to each other, but tracking at freeway speeds is going to suck. bad.

 

[Box Rocket]

Caster plates and stock arms should get the caster within stock specs with the lift that's on the truck. This is why I suggested arms AND plates, rather than just stock arms with no caster correction. Just trying to think of ways to better isolate where the noise/vibes are coming from.

 

[digitalmarker]

I have the IPOR Skid Plate and it's lower the transfer case 1/4 inch.

Did you have vibrations before you installed this? And did 1/4" drop help fix it?

What kind of a drive shaft is that? Looks like spicer joints?

Also, are you using factory bolts to hold it in place and are they long enough with the 1/4" added spacing? Or did you get longer bolts?

 

[digitalmarker]

Couple more thoughts. First of all, I'm not sure you're really at 4" of lift. The 20" hub to fender stock measurement not consistent. I've found several examples of stock height trucks at 21" and even a couple at almost 22". Of course there are some lower than 20" too. In addition, I went back to look at my notes from when I first installed my Slinky stage 1 kit. I installed it with Darren McRae looking over my shoulder. We confirmed my truck at stock height was 21" and the lift came out right at 3". My hub to fender measurements were the same as what you have, 24". So, you may believe you have 4" of lift, but that's debatable. Sounds to me you are right about where you should be for lift height with a 3" Slinky kit. That's not critical information but I wouldn't let the lift height concern you too much.

Fair enough - and agreed it's probably not the real issue here. It is the exact same lift my buddy has, with the exact same accessories in the front of the truck -we have the same bumpers, siders, etc. The only difference is he has an extra battery in the front, and I don't. Can't imagine the weight of the batter would throw off my angles.

I went back to read earlier posts and didn't see anything about the ujoint/pinion angle at the rear diff. I would confirm that your angles are correct with the rear DS flanges (as you know, should be parallel). It's entirely possible that vibration from the rear DS could be felt farther forward in the drivetrain. With the front shaft removed and no perceived vibration from the rear shaft with just the rear in place, might not guarantee that there's no vibration in the rear. It just might not be noticeable without the load of the front shaft in place. When that front is loaded, rear vibration could be intensified. If I were betting money, I wouldn't bet that this is your problem, but it's still a possibility. So I'd double check for slop in the rear u-joints and slip joint and that the shaft is in phase and flanges are parallel ( if not parallel consider longer lowers or adjustable uppers to correct pinion) . If possible, check the rear shaft for balance as well.

The difference on the rear DS pinion flanges is .4*. I can probably get it down even lower, but cannot imagine this is the problem. The rear DS was recently serviced with brand new U joints, greased, and rebalanced. The rear used to vibrate separately (with or without the front DS installed) until I installed the longer Landtank LCAs, and then further adjusted the top UCAs to get it down to .4*. There is absolutely zero vibrations coming from the back now when there is no front DS installed.

I agree with @landtank, I would remove the Delta arms and put stock arms and caster plates in and see the result. That would be identical to my setup that has zero vibrations. There are several others with this same setup also that don't have vibrations. If you still feel vibes, I'd pull the stock arms and plates and put your Slee arms back in and see the results. If one of the setups doesn't have vibes I'd stick with those arms.

I sold the slee arms. The vibration was just as bad with them as it is with the Delta arms, so swapping them didn't really make a difference. Along with the other parts I installed, I put in a brand new front axle housing - my old one was bent, which I could tell by the alignment camber reading, and the truck pulled pretty hard to the right. I really do not want to hack up the brand new axle housing to test a theory. My buddy is going to find his factory radius arms with the OME caster correction bushings, that is the closest I am going to get to restore it to "close to factory".

You've ruled out anything with the tires, correct?

I swapped the tires front to back and side to side in the past. It didn't change anything. I was going to install smaller tires from my Tundra this weekend, but since the vibration only happens with a front DS installed, I figured it would be a waste of time. Plus I spent the better part of my Saturday installing/reinstalling various combinations of the two front driveshafts and the rear drive shaft to see what is causing vibes and when.

I think the next two things I want to try are wiggling the cross member like some of the others in the thread have suggested, and trying to lower the TC/transmission by 1/4" with a spacer like Darren suggested.

The only concern I have with the 1/4" spacer method is whether it will affect/damage the shift linkage to the transmission and the transfer case shifter. But sounds like a couple folks have dropped theirs by 1/4" and are not having issues.