New lift, driveline vibes. Double Cardan Rear shaft?

[baldilocks]

I can adjust the uppers more, yes. The lowers that I got are not adjustable (OME upper and lower arms)

At this point im thinking the next step is the DC shaft, I'm just looking to see if I can rotate the pinion up enough to make it work without relocating the spring seats and Panhard bar mount.

I’ve already stated that a DC rear shaft will work without relocating the spring perches. Plenty of 80’s are running the same as me and you will be hard pressed to find threads about moving the spring perches unless the owner went all out on a completely different suspension. The bow in the coil will be less than I think you are imagining.

 

[leonard_nemoy]

If you plan to add more weight to the rear, ie drawers and bumpers, than I would get that out of the way first. But like @baldilocks said, you will be good with a dc shaft and adjusting the pinion angle.

Sounds like you will have a sweet rig when finished, goodluck.

 

[reklund5]

Update:

Custom double cardan rear shaft made my problems waaaaay worse. Bummer because it wasn't cheap.

Currently back on the OE shaft and I set the pinion angle 1.5° below parallel with the tcase flange. It's got a small vibration 30-40mph but it's better than it's been before.

 

[baldilocks]

A DC shaft that is in good condition will always run smoothly if there is a 90* angle formed between the pinion companion flange and the driveline slope as long as the slope of the shaft isn’t a very steep angle which would require a lift more than 6” on an 80. They were invented to greatly simplify these matters. Your shaft is either bent, unbalanced , or built with defective parts if your pinion is set up as I described.

 

[reklund5]

A DC shaft that is in good condition with always run smoothly if there is a 90* angle formed between the pinion companion flange and the driveline slope as long as the slope of the shaft isn’t a very steep angle which would require a lift more than 6” on an 80. They were invented to greatly simplify these matters. Your shaft is either bent, unbalanced , or built with defective parts if your pinion is set up as I described.

That's my suspicion as well- I had the pinion setup correctly for the DC shaft.

It was *much* worse than the factory setup. I need to have the DC shaft checked locally and see if something stands out. In any case, I'm not holding my breath for getting any money back on it.

I'm beyond frustrated with the whole thing at the moment.

 

[landtank]

You can’t set pinion angle in the air, truck has to be on the ground.

 

[RickyLemons]

Just get lower rear springs.

 

[thatcabledude]

Just get lower rear springs.

Or add the anticipated amount of weight to the rear before you did all this. OP, you’re doing a lot of mods to something that’s going to change when you add all that stuff you mentioned.

 

[reklund5]

You can’t set pinion angle in the air, truck has to be on the ground.

Yes, I'm very aware of that. The photo was just showing the custom shaft.

 

[NorthWA]

Just curious as I have a 2-2.5” lift up front. What size delta arms did you go with? Did those cause the front vibration that caused you to go dc shaft up front?

 

[reklund5]

Or add the anticipated amount of weight to the rear before you did all this. OP, you’re doing a lot of mods to something that’s going to change when you add all that stuff you mentioned.

I've added static weight to simulate the load of drawers and the bumper with no change. Realistically, lowering the ride height even 1.5-2" won't change the driveline angles much. My point of contention is that many people have installed a larger lift than mine and don't have issues (or are more willing to put up with vibrations)

I am being admittedly picky about it- but I feel it could still be better. Perhaps I botched something in the R&P install. More stuff to check and recheck. I'm going to try and get another set of eyes on things this weekend and see if I missed something simple.

The engine is coming out for an overhaul this winter, so that'll be a good chance to do motor mounts and the trans mount. I'm sure when it's all said and done it will be something simple I've overlooked.

 

[reklund5]

Just curious as I have a 2-2.5” lift up front. What size delta arms did you go with? Did those cause the front vibration that caused you to go dc shaft up front?

I went with the Delta 3" long arms. Probably could have gone to 4", but they don't make those with the extra length I was after. I feel it was a combo of lift and caster correction that necessitated the front shaft. It's super common on an 80 to need that DC up front. I took the front shaft out of a low mileage T100 and had it re-tubed. It's working perfectly.

 

[nukegoat]

Could be rear output bearings, pinion bearings, etc. lots of other things involved.

Does it vibrate regardless of whether it's in drive/coast/float?

 

[landtank]

Yes, I'm very aware of that. The photo was just showing the custom shaft.

from the pic it looks like its setup for a DC shaft. it's probably the angle.

 

[reklund5]

Could be rear output bearings, pinion bearings, etc. lots of other things involved.

Does it vibrate regardless of whether it's in drive/coast/float?

yes, the vibration is pretty consistent anywhere between 30-40 mph. Worst at about 37mph.

Output bearing appeared fine when I had the tcase apart to remove the studs in the flange for the custom shaft. I do have a new bearing on hand here, just haven't installed it yet. As I've said- there was no vibration prior to the lift/gears/lockers so I have a hard time blaming the output bearing.

Gear install went just fine, like the dozens I've done before without issue. Nothing to indicate something went wrong- no noise from rear diff or excessive metal in the oil when I changed it to make me think something is amiss- although I did change it all, so it is a potential source of my issue.

 

[reklund5]

from the pic it looks like its setup for a DC shaft. it's probably the angle.

Corrrect- I did alter the pinion angle so the pinion flange is perpendicular to the driveshaft at ride height. I tried it up 1º,2º,3º and down 1º,2º,3º from there with no change. Something with that custom shaft is no good, as it has a violent vibration at about 40 that causes the entire vehicle to rattle and shake. The sunroof rattles so bad in the tracks it hurts your ears. I took it out, and reinstalled the factory driveshaft, and set the pinion angle parallel to the t-case output at ride height. Then moved it down 1.5º and it's about as good as its ever been since the lift. Slight vibration 30-40mph, and only growls on decel over 60 if the slip spline isn't greased well.

Again, I can't be the only one to have these springs installed- and everyone else isn't battling a vibration. I'm missing something. Also, earlier in this thread you asked about the measurement from wheel center to flare in the rear. Drivers side is 25.5" and passenger side is 26.25" Photos are from just a moment ago, Northern NV is doing its best impression of the PNW this morning...

 

[landtank]

Corrrect- I did alter the pinion angle so the pinion flange is perpendicular to the driveshaft at ride height. I tried it up 1º,2º,3º and down 1º,2º,3º from there with no change. Something with that custom shaft is no good, as it has a violent vibration at about 40 that causes the entire vehicle to rattle and shake. The sunroof rattles so bad in the tracks it hurts your ears. I took it out, and reinstalled the factory driveshaft, and set the pinion angle parallel to the t-case output at ride height. Then moved it down 1.5º and it's about as good as its ever been since the lift. Slight vibration 30-40mph, and only growls on decel over 60 if the slip spline isn't greased well.

Again, I can't be the only one to have these springs installed- and everyone else isn't battling a vibration. I'm missing something. Also, earlier in this thread you asked about the measurement from wheel center to flare in the rear. Drivers side is 25.5" and passenger side is 26.25" Photos are from just a moment ago, Northern NV is doing its best impression of the PNW this morning...

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That’s a tall truck. I have no experience with lifts that high or the shaft you are running. But since the factory shaft performs better it would seem the DC shaft has a problem. One thing about our factory rear shafts is that the spline length is rather short. As as you lift the truck you start to sacrifice spline engagement which can accelerate wear and induce vibrations. So I’m not surprised the factory shaft is not doing so well.

The 30-40 mph vibe might be tires.

 

[baldilocks]

My rear hub to fender measure more than yours by a little bit and I had a lot of trouble making a stock shaft work due to it’s over all slope being 13* hence my switch to a rear DC shaft. It’s been fine ever since and I’d say I have a low tolerance for vibrations and noises of any kind.

Your rig does exhibit a rather extreme amount of stinkbug which may actually have your T-case output pointed upward. I know you figured in a heavy rear bumper and drawers at some point but I have never heard of anyone pairing 2” fronts with 3.5” rear springs. Before going down this driveline rabbit hole further you might consider either picking up some lower lift rear springs for now or install the drawers and bumper and whatever else at the rear of the vehicle to see where your current springs land you up. All this once you have determined that the DC driveline itself is not defective in some way.

 

[reklund5]

That’s a tall truck. I have no experience with lifts that high or the shaft you are running. But since the factory shaft performs better it would seem the DC shaft has a problem. One thing about our factory rear shafts is that the spline length is rather short. As as you lift the truck you start to sacrifice spline engagement which can accelerate wear and induce vibrations. So I’m not surprised the factory shaft is not doing so well.

The 30-40 mph vibe might be tires.

Firstly- thanks everyone for all your input. I appreciate the thoughts. Pretty sure it's not tires, as these are the same tires as before the lift, and it ran smooth then. (The PO had these 315s put on, and had to remove the front bumper so he could turn left and right. I reinstalled the bumper and trimmed the caps so I could drive it until I did all the suspension work)

To clarify: These are 3.5" FRONT springs and 2" REAR springs. I just re-checked my invoice from Cruiser Outfitters. I had it backwards in my initial post, which has been corrected now. Again, I've added about 600lbs of weight into the back of the vehicle to simulate the load of a bumper and drawers and stuff, which brought the ride height down some but didn't make a big difference in driveline vibration. I know I'm overly picky...but I also know it can be better. Like I said, I've been building and wheeling trucks for over 20 years now...so I know when something isn't quite right.

 

[landtank]

I will say this, that’s one strange looking drive shaft. The distance from the flange face to the associated U-Joint is substantial. On Toyota shafts that distance is as small as possible. This helps minimize the operating angles. And, there are weights on that shaft, right.