Been having some bad vibes at speed and decel

'69 RR

TF-727 Trans

8-3/4" Rear

Stock Height Leafs

OEM Pinion Snubber

Pinion snubber has a ~2.5" gap and apparently just barely touches under acceleration (grease test)

New U-Joints and output shaft bushing.

As she sits (level ground), everything measures dead flat at 0* (tail shaft, drive shaft and rear), which is probably the source of my bad vibes








I've searched and it seems everyone has their own opinion on how much pinion angle should be run

So before I go ordering shims, I figured I'd post up and ask.

 

driveshaft angle vibrations are at speed only not decel. They also only show up at 30mph and then 60 but go away at other speeds.

Sounds like you have another problem sorry.

 

I vibe is on and off at speed.

If I hold her steady at about 60-65, I get a pulsing vibe about every second or two

She also has a bunched up tube in the RR tire that needs attending (waiting on larger valve stems to run tubeless), so that may account for the vibes on decel, but I've had the high speed vibe since day one (before I bunched the tube)

 

How about the left right angle? if the trany bushing is worn and the tailshaft is off to the right..or the rear axle is is slightly forward on one end, or God forbid the car is bent slightly.
do you know for a fact that the drive shaft is not bent? or has a dent in it maybe from a vise? Is it balanced maybe it tossed a weight?

 

Frame is straight

First thing I did was measure her with a Spanesi Touch and she was within spec

As for the drive shaft, my next step was to have it balanced after I get the tube situation fixed, but it passed the chalk test when I installed the stock leafs, so it shouldn't be out by much if at all

Thing is, 0*/0* while sitting just can't be right

I figure at least 2* for a street car, a little more for street/strip use, but I'd like to hear some feedback first

 

what i know is the angels have to be the same be it 0 or 2 its when they get off at a uneven angl; they will speed up and slow down as they rotate i had a heck of a time getting mine aligned after the 518 install i had it at 3 and now i have raised it to 1 it's nice and smooth but the pinion moving up and down, needs a snubber that will control it until the upgrade on suspension.

 

per: Ronnie Sox. the pinon down 2-5degrees. rocker panel front 2-3 inches lower than the rear.

 

Rule of thumb is 2.5' down. The cruising pulse or drone with the other vibe has me thinking out of balance issue.

 

1---The one photo of your tool on the third member casing is NOT measuring the pinion angle.

You MUST measure actual PINION SHAFT angle, and the casting is not aligned in theat manner. If you cannot get a tool on a flat machined face of the pinion shaft/ yoke, you may have to pull the drive shaft and put the tool on the face of the yoke.

2--The only two angles that matter are the vertical angle of the transmission shaft and the vertical angle of the pinion relative to each other or each relative to "ground level." By that I mean that "ground" is only a constant so that you can compare BOTH TRANSMISSION AND PINION SHAFTS. It does not matter if the car is level so long as both shafts are measured WITH WEIGHT of the car on the ground as it sits

3--The angle between the piniion and transmission shafts is ideally ZERO under acceleration. By "zero" I mean the shafts are PARALLEL to each other. Zero angle has nothing to do with drive shaft angle or with ground angle. ALL you are concerned about is the transmission shaft and the pinion shaft. Obviously this angle changes with power level, with stiffness of rear springs and or traction devices or type of suspension. So you may have to play with STATIC angle to get "running" angle correct

4--GORT You could not possibly get the horizontal angle off enough to matter. There is simply not enough room in the engine compartment or the rear crossmember to move the engine that far, and if you moved the rear axle enough to matter, the car would be undriveable. In the case of something like an engine swap in a 4x4, this might be a factor.

5--What I would do is order yourself a device called an "angle cube" as it is smaller and easier to "get into" places

This may not be the cheapest, but this is the device:

http://www.amazon.com/iGaging-Magnet.../dp/B0035MIQ6U

To measure the transmission shaft, do one of two things. If the front yoke has machined flats, carefully place the angle cube on the flat of the yoke. If there is any question about whether these are machined "true,"...............

Remove the drive shaft. place the angle cube carefully flat against the end of the shaft and get your angle to ground

Same deal on the rear. You need to find "something" on the yoke that is machined. You may have to remove the shaft, roll the car so the yoke is vertical, and place the cube across the front of the yoke.

6--"Assuming" that the pinion should be "down 2" or whatever SHOULD be only referenced to the TRANSMISSION SHAFT angle, NOT ground level. One last time, the only angle that matters is the relationship of the transmission shaft to the pinion shaft.

 

--GORT You could not possibly get the horizontal angle off enough to matter. There is simply not enough room in the engine compartment or the rear crossmember to move the engine that far, and if you moved the rear axle enough to matter, the car would be undriveable. In the case of something like an engine swap in a 4x4, this might be a factor.
So you're saying that a damaged rubber bushing allowing the transmission tail shaft to move to the right and a worn motor mount allowing the engine to settle to the right will not affect the angle enough to cause a binding situation?As long as the relative angles of the output shaft and the pinion are aligned in the | | and the - - are equal?
That's what i thought i said

P.S. THATS A COOL ANGLE BLOCK.

 

OK, here's a little video showing where I'm at under load (4:15 goes from a dig)


I'll get her back on the lift and re-check all angles.

 

OK, so I just got her back on my level lift and measured again flat on the shaft and on both yoke joint cups using a short impact socket.

Both the DS and Pinion still measure out at 0* while the trans yoke measures in at ~.5* (probably since I burned off more than a 1/4 tank today)

Not much of a difference compared to the readings I got last night.

So if both the trans and rear are completely level as she sits and share the same centerline, where do I go from here

 

What about a bent or dented drive shaft is it new maybe it tossed a weight? and if all your mounts are solid ?

 

If I understand your measurements, you say the transmission is neg 5, so do you mean it is down at the back, while the pinion is level?

Think about this-----------this means that the pinion is ALREADY UP in comparison to the trans, and as torque comes on, it can go nowhere but up FURTHER

Offhand I'd say stick some 3* shims to point the pinion down some and go from there.

I would also double check the driveshaft. Remove the shaft. Carefully inspect the front U joint to be SURE all clips are in place and that it's the correct joint, and then "move" the yoke in all directions on the shaft. It should move smoothly with no rough spots in the movement.

Check that the rear joint is the proper one and that the pinion yoke is in perfect shape. You ARE running the clips on the rear yoke? I believe most Mopar pinion yokes need the rear joint cap clips installed to properly center the joint.

Be sure the pinion yoke--the saddle--where the joint sits is in perfect shape, that the joint fits in there firmly with no movement, and that there's no dirt or debri under the caps.

 

No, the yoke was -.5* (-1/2*), which is pretty much on par with the 0* reading I got the night before.

Basically, the trans and rear share the same center line while sitting with full weight since both yokes and the drive shaft itself measure dead flat at 0*

I replaced both U-Joints about 5 weeks ago, but found the rear joint had gone bad earlier this week and replaced it.

Yes, it's the correct part number (albeit an off the shelf brand) and all of the clips are in place (required since the yoke doesn't have centering tabs).

I'm pretty sure it got torn up from bowing above the center line under acceleration

 

Tail shaft bushing in the trans can cause the same thing, just sayin

 

It had very little play, but I had it replaced anyways just a few days ago.

 

I really think it's time for shimming. With your springs and all that torque I'd think about 4 but probably go to 6 down.

 

OK, since it will be raining all week, I decided to pull the DS earlier and will be dropping it off at the driveline shop in the morning for balancing and possibly upgrading to heavy duty lubeless joints if they have them.




Still debating between 4 and 6 degree shims, so I'll see what they suggest and go from there.

 

OK, a little update.

Last week, I had dropped off the drive shaft to get balanced just to rule it out, but the drive line shop had a problem with their balancing machine, so I picked it up on Saturday. They had already installed new Spicer lubeless U-joints, but didn't charge me for anything since they weren't able to balance.

Anyways, I installed a pair of 6 degree shims today and most of the vibration is gone

I have yet to take new angle measurements as my flat lift is occupied, but here's another video showing the results...


As you can see, under load, the DS looks straighter than in the previous video.

The little vibration I have left is most likely due to right rear tire that still has a bunched up tube I have to address.

 

I have a question that pretains to this issue, however reading thru this thread didnt exactly give me the answer i was looking for....

Im installing a rear 4-link on my 72 RR (440+727+dana60) and need to decide what angle the pinion should be at??

Its no surprise opinions are all over the place, but im looking for more of a solid number. Im not 100% sure but im guessing the recommended angle of the rearend in a leaf spring car is different of that in a 4-link car.?

Ive heard + or - 1*, up to 2*, even anywhere between 4-6*.....at first glance it appears the dana60 that i bought (set up for leafs mind you) is currently at +1* (pointed down towards the roof). The stock 8.25 rearend that came in the original 318 car however appears to be at +4.5* (pointed towards the roof). the 8.25 measurement was taken with the suspension loaded, the dana was not.

I know its alot of questions, but i really appreciate your guys' input!

So bascially im going from a stock 318, 8.25 rearend, leaf spring car.......
to a super modified 440 stroker, 727, dana60, magnumforce front suspension (with 2" drop spindles), rear 4-link car.....lol i need help