Installed D44 rear, vibrations at 20mph

Hi all,

I just wrapped up installing a Dana 44 rear axle that I purchased from East Coast Gear Supply (they make new casting, bolt in axle assemblies). I just went on a few test runs this morning and now have a vibration / shudder that starts at 20mph and picks up with speed. It lessens a bit when I take my foot off the gas, but is still there.

It seems as though there are three potential things that might be causing this.
1) new disc brakes / parking brake
2) improperly installed gears
3) driveshaft angle / u-joints

Of the three, I think a brake issue is the least likely. It doesn't pull to one side and the vibration overall lessens when my foot is off the gas. I think the most likely cause is the driveshaft angle / u-joints, but I have a hard time accepting that my small lift (which has a TC drop already, so angles should be good) gets vibrations at a measly 20mph.

A few relevant facts:
* My XJ has a 1.5" lift from Upcountry leaf and coil springs.
* It formerly had an 8.25 and never had any vibrations before
* It has a small TC drop installed currently

What do you guys think? Troubleshooting ideas?

I'd be looking close at driveshaft and ujoints.

even unbolting the driveshaft and turning it 180* in the yoke can affect vibes.

Make sure the joint is seated properly in the yoke, pinion angle is correct, lastly try removing the front driveshaft incase the cv is dry or beat.

how new are the driveshaft u-joints?

DS u-joints are original (101k on them). I have some new ones laying around so I'll change them this afternoon and report back. Nevertheless, I had no issues with the 8.25, which from my understanding has a very similar pinion length.

Did you purchase an empty housing, or a fully built and assembled rear end? If you bought it as an assembled unit, id be calling ECGS.

It's a fully assembled rear axle, with new gears, new discs, etc. I'll be calling ECGS first thing on Monday.

You could remove the rear driveshaft and see how it goes running in 4 Hi. As Digger said look to the driveshaft and u-joints. Any changes to running angles with worn u-joints can create vibrations. It isn't clear why you have a TC drop with Upcountry setup unless you went above and beyond the Upcountry setup.

If they dont answer monday, it could be because of MLK's birthday. Dont get angry when they ask if there is fluid in it, it happens.

To follow up on this...

The driveshaft slope is 10* and I measured the pinion angle to be roughly 0* based on measurements take on the face of the yoke and on the flat spots on either side of the diff cover in the back. This equates to a 10* pinion / driveshaft angle.

I found a previous thread that mentioned that the stock pinion angle is 7.5*. Can anybody verify that? If true, I'm a bit peeved. I ordered the axle with a "stock" pinion angle (as opposed to an additional offset to use in lieu of shims with a SYE set up).

Chase from ECGS said that the pinion angle is "a bit high, maybe 2 degrees". He mentioned that I could shim the axle or remove the TC drop (not sure how that would help?). Shimming the axle isn't really a good solution in my opinion. First, shims should't be needed in a non-SYE set up and, second, I shouldn't need shims for 1.5" of lift!!!

I still need to install the new u-joints and see if that makes a difference.

Thoughts?

I don't see anything wrong with using shims whether or not you have a SYE.

I don't recall the factory pinion angle of the D35, 8.25, or D44. In the ball park of 7.5 for at least one of them. Extended shackles will alter this angle but it sounds like you have stock shackles with Upcountry springs? If so, why the transfer case drop?

I am confused about the 0 degrees. Are you saying they shipped you an axle where the flats next to the cover are exactly perpendicular to the ground?

Also, keep in mind that withOUT a SYE, the u-joint angles at the transfer case and pinion are supposed to be at/near each other. So far in this post I've only read about the pinion angle unless I'm missing something.

jls095 said:

To follow up on this...

The driveshaft slope is 10* and I measured the pinion angle to be roughly 0* based on measurements take on the face of the yoke and on the flat spots on either side of the diff cover in the back. This equates to a 10* pinion / driveshaft angle.

I found a previous thread that mentioned that the stock pinion angle is 7.5*. Can anybody verify that? If true, I'm a bit peeved. I ordered the axle with a "stock" pinion angle (as opposed to an additional offset to use in lieu of shims with a SYE set up).

Chase from ECGS said that the pinion angle is "a bit high, maybe 2 degrees". He mentioned that I could shim the axle or remove the TC drop (not sure how that would help?). Shimming the axle isn't really a good solution in my opinion. First, shims should't be needed in a non-SYE set up and, second, I shouldn't need shims for 1.5" of lift!!!

I still need to install the new u-joints and see if that makes a difference.

Thoughts?

Click to expand...

Pulling the TC drop would be helpful in many ways. It gets rid of extra stress on everything in front of the TC since it's not in line with factory specs. It will also change the angle of the DS and put the pinion lower relative to your TC which would solve the issue of the angle being "a bit high, maybe 2 degrees."

Shims can be needed in any setup. Sye or non sye. Without an sye you dont worry about ds angle, but tcase output angle and pinion to be parrallel- if tcase points down 10* then have pinion up at 10*. If tcase output is 0* then pinion 0*. And subtract a few off the pinion for axle wrap

md21722 said:

I am confused about the 0 degrees. Are you saying they shipped you an axle where the flats next to the cover are exactly perpendicular to the ground?

Click to expand...

Yes, that is exactly what I'm saying. Seems to me that it should be angled upwards a bit more.

md21722 said:

Also, keep in mind that withOUT a SYE, the u-joint angles at the transfer case and pinion are supposed to be at/near each other. So far in this post I've only read about the pinion angle unless I'm missing something.

Click to expand...

The TC is angled down at 3* and the DS slope is 10*. Thus, the TC/DS angle is 7* and the pinion/DS angle is 10* (as mentioned in my prior post). These seem pretty close, no?

dan1977p said:

It will also change the angle of the DS and put the pinion lower relative to your TC which would solve the issue of the angle being "a bit high, maybe 2 degrees."

Click to expand...

Not quite sure I follow what you're saying. Put the pinion lower relative to the TC?

blondejoncherokee said:

Shims can be needed in any setup. Sye or non sye. Without an sye you dont worry about ds angle, but tcase output angle and pinion to be parrallel- if tcase points down 10* then have pinion up at 10*. If tcase output is 0* then pinion 0*. And subtract a few off the pinion for axle wrap

Click to expand...

So if the TC points down at 3* and the axle is at roughly 0*, then I should be ok, right? Otherwise removing the TC drop would raise the angle that the TC points down and make the angles a little closer.

Not quite sure I follow what you're saying. Put the pinion lower relative to the TC?

Click to expand...

How I understood his comment is that he's saying they pinion is pointing about 2* higher than it should. You can fix that in two ways. Lower the pinion or raise the TC. Either one changes the relative angle in your favor if your pinion is actually too high. I'd go for removing the TC drop since you lost 1" of your 1.5" lift by dropping the TC an inch (assuming what I've seen in TC drops) and also, it causes unnecessary wear on things like engine mounts.