Help interpreting drive shaft angles... (1 Viewer)

Joined
May 13, 2014
Messages
49
Location
Hårlev, Roskilde, Denmark
After a 5" lift with 5 degree Ironman caster plates I am experiencing a grinding noise from front shaft at 25-35 mph after which it fades out. U-joint bearings have been replaced.
There is a bit of free play in the rotation direction of pinions at axle and transfer, but no play in up/downward directions. We have just fittet an airlocker to the front axle - internals are in good state.
I think the problem is with the angles of the drive shaft, and therefore I would appreciate comments on my findings:

Slope of flange at T-case: Pointing 1* up (slightly toward the engine, but almost impossible to see).
Slope of drive shaft: 13*
Slope of flange at axle: Pointing 8* up towards T-case.

So that would leave me with operating angles of 12* and 5* - Is this correct?

I am having problems getting the URL for a Photo to Work, so I have posted a direct link in below.

http://s175.photobucket.com/user/sgtsinn/media/kardan_zps35e82644.jpg.html
Would a DC shaft help?

Things I have tried already:
* tried to drive with yokes in-phase ad out-of-phase. No difference
* tried to flip front DS. No difference
* tried to drive with rear DS removed. No difference
* tried to drive with both shafts with T-case locked and unlocked. No difference

Things I haven't tried yet:
* lower gearbox with spacers - could do that but would like input on operating angles first
* fit lower springs - but that would mean having to give up the achieved lift :-(
* ???

80-series wise I am a newbie trying to find a solution... all input are greatly appreciated:) I know there is a lot of threads around, so what I am really looking for here is help to interpreting the specifics of my axle...
 
Joined
Jul 31, 2013
Messages
668
Location
Scottsdale
Pretty sure that for a normal (non-DC) shaft, your axle flange would need to be around 1* DOWN. Your flanges need to be parallel to one another, or as close as you can get them.
Driveshaft-5.jpg



This is what you have now, well without the DC:
cv_angle.gif
 

Delancy

SILVER Star
Joined
Sep 16, 2011
Messages
12,366
Location
Tulsa
Double, double cardan shaft is your only option, besides part time, or fixing the problem the right way, by cutting off the brackets and repositioning, along with C&T.

Call Jesse at High Angle with the info you posted and he'll reiterate, along with guaranteeing his shaft won't vibrate...... :)

You'll pay a premium for the insurance policy, as it'll run you around $1,400.00 using (speculated) OEM joints.
 

Delancy

SILVER Star
Joined
Sep 16, 2011
Messages
12,366
Location
Tulsa
Right thanks. If I knew for sure upfront that dc would cure the pain, it would be worth it. I will contact the ds/dc expert(s).

A double cardan shaft won't....

A double, double cardan shaft will.

I'd offer to sell you mine, but odds are it's too long. Best bet is calling Jesse at HA and discussing.
 
Joined
May 13, 2014
Messages
49
Location
Hårlev, Roskilde, Denmark
The way I read your post Landtank, I did it in a similar way, except I used my iPhone.
I first measured the slope of the shaft.
Then I removed the shaft and measured the slope of the flanges on the two pinions by placing the phone directly on the full flat surface of the flange.
So except I don't have the decimals of the digital gauge, readings should be OK? Or am I getting it wrong?

I have a manual transmission and DS is significantly shorter than the auto, so going double DC will probably mean hat the slope of the shaft will be extremly steep (only a small part of the total length of the shaft will but "solid" and not part of the double uni's)?
 

landtank

Supporting Vendor
SILVER Star
Joined
Mar 27, 2003
Messages
20,012
Location
Groveland MA
Since I only care about operating angles I skip the whole slope calculation thing and just read the angles as I laid out in that thread.

Assuming your calculations are correct you would want to remove the caster plates, install a DC shaft and do a cut and turn.

That will give you the correct angles for the shaft and get the caster back in spec.
 
Joined
May 13, 2014
Messages
49
Location
Hårlev, Roskilde, Denmark
By Cut and turn I assume you mean relocating radius arm brackets on the axle house. But if current setup with caster plates is correct (handling is now as it should be) will the brackets not have to be relocated to the same amount of caster and drive shaft wise, slope would end up more or less the same.... Trying to picture the geometry here :)
 

Delancy

SILVER Star
Joined
Sep 16, 2011
Messages
12,366
Location
Tulsa
Picture the geometry as screwed, because there's no way to maintain caster and pinion angle on a lifted 80.

You get a choice, being one or the other, and a cut and turn, which is separating the knuckle balls and rotating to correct caster, is one.

At 5" lift, in my opinion and experience, best to turn the housing to correct pinion angle and cut and turn to correct caster.

A daunting task, but the only way to do it half ass right, since relocating the axle forward, to center in the well would require custom arms, but required to "do it right".

All else is a band aid, period.

If your caster is right, actually measured, not butt dyno or iPhone, and all of the above sounds too much work, call Jesse at High Angle and he can fab a band aid that'll correct the vibration.
 
Joined
May 13, 2014
Messages
49
Location
Hårlev, Roskilde, Denmark
Ok. Thanks for the clarification. This is turning out to be more of a job than I ever anticipated, but great input, thanks.
Will have to considered if 5 inches are worth all the trouble or maybe just decrease.

I will contact either high angle or similar here in Europe for a band aid quote.

Again, thanks for the help so far
 
Joined
May 13, 2014
Messages
49
Location
Hårlev, Roskilde, Denmark
Part time is not fixing the problem. During winter or doing the long stretches of mixed gravel and sand roads on my trips to Iceland I would prefer the AWD to work permanently.
 
Joined
Jul 15, 2011
Messages
1,723
Location
Oakdale, CA
Don't worry about the slope, the operating angles just need to match for standard Ujoints at both ends(factory configuration).

Yeah, everything is stripped off the housing and clocked ~7 degrees, including the knuckles.
MAJOR operation if trying to salvage the existing brackets, etc and not using new pieces.

Has anyone even done this and not just said F it and got a new housing, etc (myself included)

You could always just bend or cut/weld the radius arms that 7 degrees

By Cut and turn I assume you mean relocating radius arm brackets on the axle house. But if current setup with caster plates is correct (handling is now as it should be) will the brackets not have to be relocated to the same amount of caster and drive shaft wise, slope would end up more or less the same.... Trying to picture the geometry here :)
 
Joined
May 13, 2014
Messages
49
Location
Hårlev, Roskilde, Denmark
I am not sure that for my purpose the efforts would equal the result. In my part of the World annual road worthyness inspection is a big thing and with this kind of irreversible modification I could end up with a car that would never be usable on public roads :-( So this one I need to consider again. Maybe a 4" front with the caster bushings although I didn't want to use these for all the obvious reasons. Drop arms may be a way... I just dont know ....
 

Delancy

SILVER Star
Joined
Sep 16, 2011
Messages
12,366
Location
Tulsa
If constrained to maintaining OE appearance, maybe consideration be given to Slee's arms....or I'll gladly sell you some Superflex arms with a front double/double shaft to match them. :)

Worth contacting Christo or Ben. Believe they've a few Icelandic customers, already.
 
Joined
May 13, 2014
Messages
49
Location
Hårlev, Roskilde, Denmark
OE apperance is an issue, even though a 5" lift is difficult to hide :) Therefore IF the car cannot pass the inspection, all mods have to be removed and than it has to be re-inspected - Upon which you drive home and fit all mods again.

Drop arms might be a path for me to choose. I wrote to Slee via a "conversation" on this forum some days ago, but so far no reply. But could just call him of course. I considered drop boxes with the obvious disadvantages they have. I would be able to maintain original rubber bushes which I would prefer.

Being new to this forum, who is Ben?
Delancy can you quote me prices for these parts? Being a manual transmission, do you in fact know if this setup could work- The shaft of the manual is significantly shorter than the auto.

Again, thanks for the help so far.
 

landtank

Supporting Vendor
SILVER Star
Joined
Mar 27, 2003
Messages
20,012
Location
Groveland MA
I'll expand on my post.

Since you have a 5* caster plates installed and 5* operating angle at the diff u-joint, if you take off the plates that angle should be close to 0* and a DC drive shaft should run properly.

But now your caster is back to being way off and the truck will drive horribly.

So now to regain that caster you would do a "cut and turn".

This is where you cut the knuckles free from the axle housing and turn them to add caster. You cut through the weld just enough to release the housing an rotate it and then reweld it.

The cut and turn method should yield up to 7* degrees of change in caster before the tie rod contact with the arms becomes too great of a problem.

This method of caster correction is much more common on leaf sprung vehicles and if you search the forums you can find a thread on how to do it.

I would however take the plates back off and confirm the drive angle for the DC shaft before committing to this.

it's not a bolt on solution but the cheapest one if you can do the work yourself and will yield the best possible results in my opinion.
 

landtank

Supporting Vendor
SILVER Star
Joined
Mar 27, 2003
Messages
20,012
Location
Groveland MA
it doesn't matter how you go about rotating the whole axle, whether its with plates, arms, drop brackets, the end result will always be the same. Either the caster is good and the drive angles are bad or the drive angles are good and the caster is bad.

You need to divorce those two from each other and then adjust them independently.
 

Users who are viewing this thread

Top Bottom