Rear driveline angle

[JR74CJ5]

I have terrible vibration, mostly in 3rd (1:1) gear at around 1500 to 2500 rpm. I suspect from research my angles are not correct between the Dana 44 and t case. My pinion points at my tcase. As if i had a double cardian ds. I have shims that appear to be clocking it this way between the d44tubes and spring "holder".

When i purchased the jeep it had a tcase drop installed. I removed this when reinstalling Transmission / tcase. I assume they were pointing at eachother for some reason, though not sure why.

Anyways, question is do you all think i should just remove those shims and see if that helps?

It is supposed to be parralel to eachother for standard style ds yes? Could this be the culprit of my vibrations, as i assume?

Ill post some pictures to show this all tomorrow.

I dont want to buy a dcj ds yet as i plan to lift 2-2.5" soon. (when funds allow)


Jr

 

[Old Dog]

It is supposed to be parralel to eachother for standard style ds yes? Could this be the culprit of my vibrations
Jr

Yes they should be parralel.
My superlift 4" springs came with deg. shims also, I left mine in and it has been ok, but I know it's not right.
Mine sits at about 12* now, I believe it's at it's limit.

 

[PaRenegade]

This may help with some insight to steering geometry.
http://mysite.verizon.net/res108eps...ilderfiles/Steering-and-suspension-basics.pdf

 

[JR74CJ5]

This may help with some insight to steering geometry.
http://mysite.verizon.net/res108eps...ilderfiles/Steering-and-suspension-basics.pdf

Wow great link man!

At first I'm like: "ah... thanks, but not talking steering" but When I got in there it's a plethora of GREAT info man!


~ JR

 

[JR74CJ5]

I know these are crappy pics...

T case output:

Although angle is difficult to see from lic, you can see the angle (visually) is different that the rear:

I'm going to try to remove these shims: (again hard to see, but they are between spring tops and guide on the axle tube for springs. and are angling the pinion upward towards Tcase)

 

[PaRenegade]

That write up is great isn't it.

Yes, you probably need to angle the pinion down more by the looks of it. Removing the shim should help make it a sharper angle like the front of that shaft is.

 

[Razorfish]

I was helping my friend with his *cough* Cherokee and we found there was a little trial and error getting it correct. We first put the shims to get what looked like the correct angle but then had to just try different shims with a little more/less and road-test to get rid of the vibration.

Also installed a fixed yoke (or whatever it's called), CV joint and new drive shaft.

 

[PaRenegade]

It's a double cardan joint or CV (constant velocity) joint. This would eliminate needing to do any shimming because it allows you to have 2 different angles. But it's a more expensive way to go because of the additional parts needed.

 

[JR74CJ5]

Yeah not quite ready to get one yet, though it's in the plans later. I'll be doing a very mild 2" - 2.5" lift soon, and expect I'll need to have a little longer travel then for the rear DS. Don't want to buy it twice. At that point I will plan to correctly set up the angles etc (whether that's shims or actually cutting / rotating).

Basically looking for validation that I'm thinking along the correct lines that my pinion "should" be set up parallel to tcase output yoke for this stock style ds. (which I've received )

And possible a in "measuring angles for dummies" style way of measuring the angles. I can do a flat piece of paper with a protractor but wondering how you guys check accurately the angles.

Keep in mind I have not fully read through your link above yet, and get where / what I am measuring, just not sure the best way to measure it...



~ JR

 

[BusaDave9]

It's hard to fix a vibration problem over the internet but it looks like you have a steeper angle at the TCase than the rear axle yoke.
Those angles should be close to the same.

If the U Joint angles on a drive shaft are not strait (they never are on an off road vehicle) then they actually speed up and slow down on each rotation. This can produce a bad vibration. But a drive shaft is made so the vibration of the front U Joint cancels the vibration of the rear U Joint. This works great if the the angle of the front U Joint to match the rear. This is how every manufacture makes vehicles.

But this only works at small drive line angles. The UJoints don't like too much angle so when you lift your jeep you may have to angle the rear differential upward. This can be done with angled shims at the leaf springs. Then to keep both u Joint angles the same you can lower your TCase. If the drive line angles get to be too much you should then go to double cardan joint or a CV joint at the front of the drive shaft. A double cardan joint is 2 U Joints together.

These 2 U Joints cancel each others vibrations. In that case the U Joint at the differential should not have any angle. To keep it from vibrating it should be strait like this.

Now you can see how the pinion is much higher than the manufacturer intended.

Also that link that PaRenegade gave covers this. It starts on page 21.
http://mysite.verizon.net/res108eps...ilderfiles/Steering-and-suspension-basics.pdf
You also may want to rotate the front tires to the rear of your jeep and vise versa. Maybe a tire lost a wheel weight.
Keep in mind that an out of balance wheel will give a much different vibration than poor u-joint angles.
If it is the drive shaft angles it is like the drive shaft tries to speed up and slow down as it rotates. It is hard to explain but that is a rotational vibration that feeds back into the Transmission and tcase.
If the wheel is out of ballance it is not like it is trying to speed up and slow down. It is more like the extra weight wants to spin outward and vibrate the axle.

If it is the drive-shaft angle you can lower the tcase and see if it goes away. If so you could raise it back up and install a driveshaft with a double cardan joint (like a CV).

 

[PaRenegade]

I would much rather shim than cutting and rewelding the perches. That brings in a whole new set of issues on keeping things aligned and symmetrical, unless you have skill at welding and fabrication of steel. But that's just me.

I have a magnetic protractor that works well for measuring angles. Sometimes it can be difficult to get a flat perpendicular surface to measure from but if the driveshaft is off then you can use the yoke face that the straps or bolts are normally going thru.
Here's the protractor I have, and it's under $10.
Sears: Online department store featuring appliances, tools, fitness equipment and more

 

[JR74CJ5]

If it is the drive shaft angles it is like the drive shaft tries to speed up and slow down as it rotates. It is hard to explain but that is a rotational vibration that feeds back into the Transmission and tcase.

If it is the drive-shaft angle you can lower the tcase and see if it goes away. If so you could raise it back up and install a driveshaft with a double cardan joint (like a CV).

The description above is exactly what I'd describe mine as also. And this issue hasn't just started. It's just been on back burner, but already lost my tcase output ujoint once on the freeway at 65mph, so thinking I need to move it back to the front burner now before much more is done.

Since I do not have much lift, I think my rear pinion has just been angled up with shims by the PO for ?? reason. I need to tear into the rear end and springs of this thing anyways, so figured while I do it, I'll remove the shims and check the angles. If looks good I'll take it for a spin after full reassembly, and if not gone, I'll start thinking the double C.J. driveshaft. Again, would like to wait on purchasing that until after my lift is completed. Wouldn't you agree Dave?

I hated the Transfer Case drop that was there when I bought it, so did not reinstall it after tranny work. I was a noob and didn't understand the geometry and physics involved

All,
~ JR

 

[JR74CJ5]

I would much rather shim than cutting and rewelding the perches. http://www.sears.com/shc/s/p_10153_...o=1&blockType=G1&prdNo=1&i_cntr=1328125156855

I would much rather as well, but I fear the cutting and re-welding is the actual "correct" way to do it.

However, I'm not quite there yet

And thanks for the link to the protractor / angle finder bud!

I still am unclear on the HOW part of the measuring. I have basicaly the top pictured angle finder here:



So I would put the round connection portion at the joint center, try to keep the top portion parallel with the output yoke plane, and line up the center of the driveshaft with bottom "leg" and that should give me my degrees of angle correct? And this should be 3 degrees? Or even up to ___ degrees? etc.

 

[PaRenegade]

With that type you'll have to use a level or some means of referencing both angles to the same plane. And maybe an extra set of hands. Whereas the protractor uses gravity to move the pointer inside. It hangs freely inside and when held plumb it will always point down at the same angle, which is the vertical plane for reference to measure the two yoke angles from. It's also magnetic on one side.

What you can do, similar to what you stated but I fear you won't have the room, is put the outside of one leg against the yoke face, then angle the other leg roughly in the angle of the driveshaft, then slide the first leg along the yoke and adjust the other leg to be parallel with the shaft. That's in theory. In reality you can't slide against the yoke with the driveshaft in place, but when it's not then you have no shaft to make parallel with. Maybe you could tie a string between the two (d.s. removed) with both yokes in the same vertical position. When your talking half degrees it's easy to be off when eye-balln' it.

 

[Old Dog]

lots of good info here..Pirate4x4.Com - Extreme Four Wheel Drive

 

[BusaDave9]

First rule: The front u-joint angle should match the rear u-joint angle (withing 3°). It looks like the front u-joint angle is greater than the rear ujoint angle. To shim the rear axle to make both u-joint angles match you would have to shim the axle down. That is not the normal direction to shim an axle.

​

This next picture I added a blue line showing the front edge of the yoke. This is what PaRenegade was talking about checking the angle against the yoke. The yoke on the diff is the blue line. You can see the yoke almost points to the drive shaft with very little angle at the drive shaft.

In reality you can't slide against the yoke with the driveshaft in place, but when it's not then you have no shaft to make parallel with.

​

Second rule: do not icrease either u-joint angle too much. A u-joint at a high angle will experience too much stress and wear. This is why I say you would be better off lowering the TCase to get both angles the same. Better yet install a double cardan joint drive shaft.

 

[JR74CJ5]

Thank you both (and all others) very much.

I took the jeep to the local driveshaft shop here. They have told me the same thing you have all been saying. Basically if i remove the shims now, the angles will be closer to even, but way to large.

He reccomends double cardian joint with new Dana 20 yoke for it, and new shims (which i needed anyways). $350 ish total

Then i will need to have it lengthened after i get my lift for around $100.00...


But... Ill get rid of this vibration without needing to lower tcase... Which is what i ultimatley want...

Hmmm. Federal refund may have been smaller than i thought sweetheart...

 

[JR74CJ5]

Well bit the bullet and ordered my CVO Driveshaft.

Local shop measured it all out for me and is doing the build today. Also ordering my adapter for the Dana 20 .

Still can't imagine why I would need it with barely any lift.. I have stock high springs, and slightly larger shackles. 3/4" if I calculated correctly. (4.5"-3")/2=.75" That's (my shackle bolt centers-stock bolt to bolt)/2=Lift in shackles

I do run 33" tires...

Will keep you all informed. Not sure if he's just upselling me, but seemed like he knew what he was talking about, and most of it made sense according to the info I've gathered from you all.

Thanks for all the info!

~ JR