Pinion angle

[Eagle_SX4]

I have been having some vibrations from what I think is the incorrect pinon angle. According to this thread on driveline angle the rear pinon should be about 1-2 degrees down of what the transfer case output is at.

 

I have measured the angles on both my transfer case output shaft and rear pinion. According the the angles it looks like my pinion is about 4 degrees above the transfer case. 

My question is will a 5 or 6 degree shim work better?

[ghetdjc320]

Do you have a front driveshaft? If so, try removing it and driving around first. As for a shim, don’t point the pinion into the ground. No need to go below parallel. You can keep the pinion at 0 or a degree or two up with no ill effects. It could just be a gas u joint. 

[Eagle_SX4]

Maybe some more info would help.

 

Most of the driving I do I never get above 60 mph and never have any issues up to 60 mph.

 

I have to drive 45 minutes away to reach the freeway which is when I start to have issues. This problem only happens when I am doing 70+mph.

 

Problems start when doing 70+mph down the freeway and hitting a bump. The u-joints in my rear driveshaft bind up and cause the entire drivetrain to shake back and forth violently. My steering wheel does not shake but the transmission shifter flops back and forth. It doesn't stop till I pull on to the shoulder and down to about 10 mph then it is fine again until I hit another bump at 70 mph. Hitting bumps below 60 nothing happens.

 

I replaced my u-joints last summer both front and rear and checked them today and no signs of wear or binding on any of the u-joints. Everything move freely.

 

I thought my issues where fixed when I shortened my Chevy drop shackles which did help some and why I am looking to get some leaf spring shims to help even more.

 

Another thing that might be an issue is driveshaft length. How much travel should the slip yoke have on the transfer case? I only have about 3/8 inch of compression before it bottoms out. My driveshaft is 48.5 inches center of cap to center of cap. Which as far as I can find is correct for an AX15 and Dana 44 rear axle.

 

Fully seated in the pinion.

 

Bottomed out of the transfer case.

 

Also I did remove my front driveshaft and drove on the freeway and the issue was still there.

[ghetdjc320]

That’s a super short up travel there. Rotating the pinion may help to lengthen the distance between the tcase and pinion. 

[89 MJ]

I was always told the pinion angle should be within 2.5 degrees of parallel. If they make a 3 degree shim, that is probably the way I’d go. 
 

And let me guess, you’ve got an XJ rear end in your Eagle? That’s what’s in mine and despite everything I read about the pinion angle being correct, it’s not.
 

I have probably the same amount of travel in the driveshaft, but no vibration, even at 75. Maybe it has something to do with the wheel base, but I’ll let someone who’s smarter than me chip in for that. 

[Eagle_SX4]

19 minutes ago, 89 MJ said:

I was always told the pinion angle should be within 2.5 degrees of parallel. If they make a 3 degree shim, that is probably the way I’d go. 
 

And let me guess, you’ve got an XJ rear end in your Eagle? That’s what’s in mine and despite everything I read about the pinion angle being correct, it’s not.
 

I have probably the same amount of travel in the driveshaft, but no vibration, even at 75. Maybe it has something to do with the wheel base, but I’ll let someone who’s smarter than me chip in for that. 

This problem is in my Comanche. I think it might have more to do with the driveshaft length than the pinion angle.

[89 MJ]

56 minutes ago, Eagle_SX4 said:

This problem is in my Comanche. I think it might have more to do with the driveshaft length than the pinion angle.

I see that now that I’m looking closer. I think you might be right. 

[gogmorgo]

What condition are your engine and trans mounts? Leaf spring bushings? Have you rotated the tires to see if the problem follows to the front axle? What do your shocks look like?

 

You may be onto something with driveshaft length. Looks like you’re running a later transfer case with the sealed output and external slip yoke? They’re supposedly a little longer overall so that could affect your desired driveshaft length.

I wouldn’t really expect that to cause vibration on its own, but hammering the driveshaft into the tcase if you run out of travel could damage other things in ways that could cause vibrations.

[Eagle_SX4]

56 minutes ago, gogmorgo said:

What condition are your engine and trans mounts? Leaf spring bushings? Have you rotated the tires to see if the problem follows to the front axle? What do your shocks look like?

I changed the engine mounts last year. Trans mount is in good condition. Brand new General Springs leafs with new bushings last spring. This problem is not related to the tires because it happens with my studded snow tires or my summer tires. Shocks are brand new Bilstein 5100's.

[Eagle_SX4]

My driveshaft is definitely to long. I jacked up the truck with some jack stands under the frame and let the rear axle drop and the drive shaft bottomed out on the transfer case.

 

I called Tom Wood's driveshafts and they said there should be 1 inch of compression at ride height. So I will need to get my shaft shortened or get a new one made. I also need to shim my pinion down to get the angles closer to parallel. Right now the pinion is 4 degrees above the output shaft.

[ghetdjc320]

3 hours ago, Eagle_SX4 said:

My driveshaft is definitely to long. I jacked up the truck with some jack stands under the frame and let the rear axle drop and the drive shaft bottomed out on the transfer case.

 

I called Tom Wood's driveshafts and they said there should be 1 inch of compression at ride height. So I will need to get my shaft shortened or get a new one made. I also need to shim my pinion down to get the angles closer to parallel. Right now the pinion is 4 degrees above the output shaft.

Tomwoods carries the shims as well. Sound like around 3-4* should work well.

[Eagle_SX4]

36 minutes ago, ghetdjc320 said:

Tomwoods carries the shims as well. Sound like around 3-4* should work well.

Yeah I am going to get both 2 and 4 degree shims and see which works better while driving I think 2 might be best. While under load the pinion rolls down and then would be lined up (in theory anyway).

 

I am actually only about an hour away from Tom Wood's but they are really busy right now. They are only making new shafts and aren't taking any outside work right now. I found a shop closer to me that can shorten it for me and if that doesn't work then I will order a shaft from Tom wood's.

[ghetdjc320]

On 4/14/2024 at 10:46 AM, Eagle_SX4 said:

I changed the engine mounts last year. Trans mount is in good condition. Brand new General Springs leafs with new bushings last spring. This problem is not related to the tires because it happens with my studded snow tires or my summer tires. Shocks are brand new Bilstein 5100's.

Is this not the original driveshaft/axle combo? Can you shoot a picture of how the wheel sets on the wheel well?

[Eagle_SX4]

On 12/9/2009 at 7:32 PM, akamcbird said:

arg!.... did the maf wrong

:no:

 

revised.... green print is actual measures the rest is mathed out

comanche rear drive shaft lengths-eye to eye

 

'86 lwb, 2.8, tf 3speed, np207, d35 = 54"

lwb, 4.0, aw4, np231, d44= 48" d35 = 49"

lwb, 4.0, ax15-ba10/5, np231, d44= 49" d35 = 50"

swb, 4.0, aw4, np231, d44= 41.25" d35 = 42.35"

swb, 4.o, ax15-ba10/5, np231, d44= 42.25" d35 = 43.25"

 

ax15-ba10/5 (same length) are 1" shorter than aw4

d44, chr8.25 have a 1" longer snout than d35

 

can someone re confirm? sorry for the above confusion.

 

amc20 vs d35 snout difference??

4 BANGERS AND 2WD SPEAK UP!

Found this and after I measured my drive shaft I need it shortened about 3/4 of an inch.

My driveshaft measures 48 3/4. I need it to be 48.

 

There must be a length difference between the new and old style transfer cases. Can any one confirm this?

 

6 hours ago, ghetdjc320 said:

Is this not the original driveshaft/axle combo? Can you shoot a picture of how the wheel sets on the wheel well?

 

I am pretty sure it is the original driveshaft and axle. The previous owner swapped in an AX15. I swapped in a new style NP242 from the original NP231. I didn't have a picture right now but the wheel is pretty close to center of the wheel well. Maybe just a hair towards the front. 

[gogmorgo]

Once you have the rear driveshaft out, you can take it for a rip in 4hi, see if the rear shaft missing makes a difference. If it’s been hammering against the transfer case it may be bent or something, and out of balance.
I’m also not sure the standard driveshaft length charts we have necessarily apply to the later sealed output style transfer cases.
And I don’t know either that the 242 is a perfect length match for the 231, or just close enough to not be a problem in most cases. I want to say when I swapped my 231 to an early-style 242 the seal was cleaning off more of the yoke than before, possibly by as much as 1/2”. But that was a long time ago. 
The BA10 vs AX15 may not be a perfect exact match either, Advance Adapters only guarantees their swap kit to be within 1/4”. 

But with as many variables in configuration as you have changed from stock, I think it’s important to do your own measurement instead of relying on a chart of stock lengths. 1/4 or an 1/8” from stock here or there might not matter individually but together the accumulated error may be too much. 

[Eagle_SX4]

11 hours ago, gogmorgo said:

 But with as many variables in configuration as you have changed from stock, I think it’s important to do your own measurement instead of relying on a chart of stock lengths. 1/4 or an 1/8” from stock here or there might not matter individually but together the accumulated error may be too much. 

I put the slip yoke on the transfer and left the u joint off the pinion. Then I pulled the yoke away from the transfer case so that it would have 1 inch of compression and measured from the center of the cap on the yoke to the flat on the pinion and got 48 inches. 

 

I took my driveshaft in today and had it shortened to 48 inches. The shop was way faster than I thought they would be. Only took them 3 hours to get it done.

 

My truck does drive better now but it still shakes a bit. I am going to get some pinion shims ordered and get them installed. 

 

I also did drive around in 4 high with the rear shaft removed and my issues were gone so one problem fixed and on to the next one.

[Eagle_SX4]

Here is a pic of the driveshaft installed after it was shortened.

A lot more compression available. There are 3 inches of splines on the transfer case out put shaft. Plenty of room for compression and extension.

[Eagle_SX4]

Got the shims I ordered in today. They are junk and won't be getting installed on my truck. I should have just ordered from Tom wood's but I wanted to save a few dollars.

 

I ordered them from Iron Rock Off-road. Here are some pics of what I received. 

As you can see they aren't the same angle, the same height, and they aren't flat. I emailed them with the attached pictures and am waiting to here back.

[ghetdjc320]

6 hours ago, Eagle_SX4 said:

Got the shims I ordered in today. They are junk and won't be getting installed on my truck. I should have just ordered from Tom wood's but I wanted to save a few dollars.

 

I ordered them from Iron Rock Off-road. Here are some pics of what I received. 

As you can see they aren't the same angle, the same height, and they aren't flat. I emailed them with the attached pictures and am waiting to here back.

WOW, those look horrible. Yeah, just grab them from TW. You may also need a longer center pin. 

[Eagle_SX4]

Got the Tom Wood's shims installed today. They came with new pins. Just had to grind the heads down a bit to fit in to the perch.

Pinion angle is much better. Went from 4.5 degrees above the transfer case output to only 1.3(with a 3 degree shim).

 

If I need to I can lower my transfer case by finding a proper AX15 cross member. I think it is still the same one that was in the truck when it had the puegeot transmission in it.

I know that the AX15 cross members have a lower mount point that is level with the center seem of the cross member. I might just cut this up and weld it back together if I can't find an AX15 one. Doing so would drop the transfer case down 1 degree. I unbolted the cross member and lowered it down to find out out how much the angle would change. 

 

Time will tell if this has helped or not. I am still thinking the longer shackles I have are also playing into my issues as well. That might be the next thing I change.