driveshaft angle and length question

[guidoverduci]

Ok, up next is driveshaft replacement. My setup previous was WH 3.5 lift with no shims. I’m not sure if the driveshaft was stock or not. With this setup, I had no issues (that I could feel/tell), but was always concerned with driveshaft angle. Now, I have added extreme duty output shaft and my first issue is driveshaft length. I’ve attached a pic, but as it sits, there’s only about an 1.25 inches of shaft showing. This seems like not enough to me.

Second issue, angle. I measured the driveshaft angle according to various tech articles and I come up with 23°. For the pinion angle, I got 12°. So if I’m doing it (and understanding it) correctly, that is a difference of 11°. Which is too much I believe. Will the 6° shims be enough? I’d like to think that since I didn’t notice anything prior, this should definitely be sufficient and help on wear and tear. Any thoughts, opinions? I will add that there is missing weight of rear seat and roll cage which could impact things.

 

[jamesroney]

Ok, up next is driveshaft replacement. My setup previous was WH 3.5 lift with no shims. I’m not sure if the driveshaft was stock or not. With this setup, I had no issues (that I could feel/tell), but was always concerned with driveshaft angle. Now, I have added extreme duty output shaft and my first issue is driveshaft length. I’ve attached a pic, but as it sits, there’s only about an 1.25 inches of shaft showing. This seems like not enough to me.

Second issue, angle. I measured the driveshaft angle according to various tech articles and I come up with 23°. For the pinion angle, I got 12°. So if I’m doing it (and understanding it) correctly, that is a difference of 11°. Which is too much I believe. Will the 6° shims be enough? I’d like to think that since I didn’t notice anything prior, this should definitely be sufficient and help on wear and tear. Any thoughts, opinions? I will add that there is missing weight of rear seat and roll cage which could impact things.

There's something goofy in your picture, and your numbers seem way off to me.

First, The dimension from the bottom of the frame, (not the bump stop...) to the top of the axle tube MUST BE 9.5 inches. I'm looking at your tire inflation, and I see no bulge. Do you have your doors, interior, hardtop ,roll cage gas tank, bumpers, and spare tire mounted? It looks like it's sitting about a foot over the axle. I can't recall ever seeing a 3.5 lifted Bronco at 23 degrees down angle on the driveshaft. So please confirm axle to frame distance.

Second, when the pinion comes up an additional 6 degrees, the pinion will rotate and the driveshaft will get shorter. But the driveshaft angle will become less steep. So all of the numbers change as the axle rotates up.

Is your driveshaft the correct length? Nobody knows. I'm gonna say "maybe" because hopefully you are going to throw away any axle shims, buy longer perches from Wild Horses, add an additional hole 1 inch forward on the perch, add a hole 1 inch forward on the u-bolt plate, and move the rear axle back 1 inch. (to center the tire in the wheel arch.) I'm at that point on my build, and you can see the WH perches in this pic. I hate wedges, I won't install wedges, and I remove any wedges that I find. They are a bad idea, and they are a crutch and they suck. But Wild H is not dumb. They chose 6 degrees for a reason. Years of empirical data says that a 6 degree shim is about right for 3.5 lift. 5.5 needs more, and 2.5 needs less.

If you are not running a hard top, or if you don't have accessories, or if you run a front winch and bumper, then with those springs, your Bronco will be ass-high about 2 inches. Removal of the first full loose leaf, and the bottom 2 spacer leafs will get you back to a measured 3.5 inch lift. Remember that the rock crawler springs are precision calibrated to get the correct ride height at the correct static weight. If you don't have the right weight, they WILL ride high. They also settle a bit with time. To do it right, go cut a couple of 2x4's at 9.5 inch long, and place them between your axle and frame. Then take a ratchet strap and snug them down until they are tight. Then get a couple of 2x4's and cut them at 10.5 inch long. Put them between the front axle and the frame. THEN start measuring for driveshafts.

I got to that point with my 9 inch last week. You will notice that the perches are still on the floor...

 

[guidoverduci]

There's something goofy in your picture, and your numbers seem way off to me.

First, The dimension from the bottom of the frame, (not the bump stop...) to the top of the axle tube MUST BE 9.5 inches. I'm looking at your tire inflation, and I see no bulge. Do you have your doors, interior, hardtop ,roll cage gas tank, bumpers, and spare tire mounted? It looks like it's sitting about a foot over the axle. I can't recall ever seeing a 3.5 lifted Bronco at 23 degrees down angle on the driveshaft. So please confirm axle to frame distance.

Second, when the pinion comes up an additional 6 degrees, the pinion will rotate and the driveshaft will get shorter. But the driveshaft angle will become less steep. So all of the numbers change as the axle rotates up.

Is your driveshaft the correct length? Nobody knows. I'm gonna say "maybe" because hopefully you are going to throw away any axle shims, buy longer perches from Wild Horses, add an additional hole 1 inch forward on the perch, add a hole 1 inch forward on the u-bolt plate, and move the rear axle back 1 inch. (to center the tire in the wheel arch.) I'm at that point on my build, and you can see the WH perches in this pic. I hate wedges, I won't install wedges, and I remove any wedges that I find. They are a bad idea, and they are a crutch and they suck. But Wild H is not dumb. They chose 6 degrees for a reason. Years of empirical data says that a 6 degree shim is about right for 3.5 lift. 5.5 needs more, and 2.5 needs less.

If you are not running a hard top, or if you don't have accessories, or if you run a front winch and bumper, then with those springs, your Bronco will be ass-high about 2 inches. Removal of the first full loose leaf, and the bottom 2 spacer leafs will get you back to a measured 3.5 inch lift. Remember that the rock crawler springs are precision calibrated to get the correct ride height at the correct static weight. If you don't have the right weight, they WILL ride high. They also settle a bit with time. To do it right, go cut a couple of 2x4's at 9.5 inch long, and place them between your axle and frame. Then take a ratchet strap and snug them down until they are tight. Then get a couple of 2x4's and cut them at 10.5 inch long. Put them between the front axle and the frame. THEN start measuring for driveshafts.

I got to that point with my 9 inch last week. You will notice that the perches are still on the floor...

It’s about 10 5/8 between axle tube and frame. Tires are good. As far as truck weight, only thing missing is rear bench seat and roll cage. I don’t run a top, front winch, or anything else.

Once I have a better understanding of all this, I’ll dive into the axle perch idea.

 

[guidoverduci]

This video breaks down terminology pretty good. If I understand correctly, with the double carden on one side, I need to get my pinion angle within 2-3 degrees of my driveshaft. Since my rough measurements were around 23 for the shaft and 12 for the pinion, I’d need to rotate at least 8 degrees. I’m going to double check all my measurements, but mostly it paints the picture. I could be a degree or 2 off on either side, but the overall problem still exists. To the drawing board!

 

[DirtDonk]

How are you measuring your pinion angle? And we are talking about the rear end pinion, not the transfer case pinion. Correct?
From the pics the rear pinion does not look to be 11 degrees of difference. But pics do lie when the camera is at certain angles, so it's hard to say from here.

Also, I try shooting for 1-2 degrees rather than 2-3 degrees. Where did you read that? Here on classic?

I don't know the exact numbers, but a 6 degree shim bolted to the rear spring "usually" nets you about 9 degrees of correction. If I remember anyway, but the details are vague at best.
Just that by the time you factor in distance from centerline in two planes, the net change at the pinion yoke/u-joint is more than the rating of the shims by a couple/few degrees.

I agree with James that the re-oriented perch is a better method, but I'll defend our shims too, which are well proven to work to get the job done safely and for the long term for those of us that are not ready, or not able to change the perches.
The longer perches with relocating holes are a big bonus, in multiple ways. Just that the shims in this case are a workable alternative.

As long as you use steel shims that are bolted to the spring pack with the full alignment pin (bolt head) inserted into the hole in the perch, they work very well. As opposed to a shim that's simply placed between the spring pack and axle/spring perch. Which is a bad day waiting to happen.
Especially if you use the more troublesome cheap aluminum shims. Steel and bolted are the way to go, with new perches at the correct angle better yet.

And no matter what, do exactly as James recommended and don't even question lengths and angles until you set your suspension height. With your lighter than normal rig, you may indeed have to remove a leaf or three to get there.
Relatively permanently perhaps.

Paul

 

[guidoverduci]

How are you measuring your pinion angle? And we are talking about the rear end pinion, not the transfer case pinion. Correct?
From the pics the rear pinion does not look to be 11 degrees of difference. But pics do lie when the camera is at certain angles, so it's hard to say from here.

Also, I try shooting for 1-2 degrees rather than 2-3 degrees. Where did you read that? Here on classic?

I don't know the exact numbers, but a 6 degree shim bolted to the rear spring "usually" nets you about 9 degrees of correction. If I remember anyway, but the details are vague at best.
Just that by the time you factor in distance from centerline in two planes, the net change at the pinion yoke/u-joint is more than the rating of the shims by a couple/few degrees.

I agree with James that the re-oriented perch is a better method, but I'll defend our shims too, which are well proven to work to get the job done safely and for the long term for those of us that are not ready, or not able to change the perches.
The longer perches with relocating holes are a big bonus, in multiple ways. Just that the shims in this case are a workable alternative.

As long as you use steel shims that are bolted to the spring pack with the full alignment pin (bolt head) inserted into the hole in the perch, they work very well. As opposed to a shim that's simply placed between the spring pack and axle/spring perch. Which is a bad day waiting to happen.
Especially if you use the more troublesome cheap aluminum shims. Steel and bolted are the way to go, with new perches at the correct angle better yet.

And no matter what, do exactly as James recommended and don't even question lengths and angles until you set your suspension height. With your lighter than normal rig, you may indeed have to remove a leaf or three to get there.
Relatively permanently perhaps.

Paul

Thanks Paul. For measurements, I used my iPhone which has a level app (been extremely accurate when verifying against known info). While on level ground, I placed my phone against the driveshaft similar to a couple tech articles on here. 23 degrees. For the pinion, I placed the phone against the face of the yoke and it read 12 degrees.

You both mentioned proper suspension height and the possibility of removing leaf springs. Can you elaborate on why? With my current setup, I was more than happy with the height, stance, balance, “levelness”, and ride comfort. What are the gains with making it proper? It’s fairly level now, at least to the eye… why lower the rear?

 

[ksagis]

Solving graphically, I get about 12 degrees for diff ujoint difference in angle, and 22 degrees for double cardan at TC difference of angle. Pretty sloppy work by me, but within a degree or two. Need to rotate the diff up, which will also reduce the angle at the double cardan. When you say driveshaft was 23 and pinion was 12, if I'm understanding what you're saying, the pinion angle we care about is 23 - 12 which is 11. You want to drive that angle to be roughly 2 degrees below driveshaft angle.

Think it should also increase the amount of overlap at the slip joint which is going further in the direction of the concern you noted, I don't know any rules of thumb for that dimension but sure others here do. Doing a suspension stuff would give you a clear answer, but starting with previous knowledge would be good.

 

[DirtDonk]

While on level ground, I placed my phone against the driveshaft similar to a couple tech articles on here. 23 degrees. For the pinion, I placed the phone against the face of the yoke and it read 12 degrees.

I can't argue with the numbers then. Sure does not look like an 11 degree offset visually from here anyway, but we'll go with that for now.
If you use the 6 degree shims and they give you the 9 degrees I "guesstimated" earlier, then that leaves you with a pretty optimal 2 degree discrepancy.
Pretty good in most books.

But herein lies the argument for new perches tacked in place and then final welded once everything is set at final ride height.
You will absolutely need to modify that angle, using shims or newly re-oriented perches, and then measure accordingly for your new shaft (if you need one that is) with the new angle but with the current ride height.
As long as you know it's still sitting where it was before, you're ready to go.

You'll want to re-measure the two angles after any modifications (shims, etc) to verify what you got.
The fact that you had no problems you were aware of is pretty good, but it's not correct by the book or by most of our experiences. So you do need to change the pinion angle.
With that much discrepancy, most of us get a vibration upon deceleration. Rear pinion pointed too high and it vibrates under acceleration, too low and it vibrates under decel.

You both mentioned proper suspension height and the possibility of removing leaf springs. Can you elaborate on why?

Because as mentioned yours looks high. As is often the case with topless and incomplete Broncos on brand new leaf springs.
But are you saying that you've been at this height with these springs for awhile now and driving? If so, then that's different...

With my current setup, I was more than happy with the height, stance, balance, “levelness”, and ride comfort.

Then in my book you're pretty well set. Just leave it as is, and set up your pinion and driveshaft length based on the height you have been running and are happy with.
So you have changed nothing in the suspension during this process and you are working with all the same stuff you had before?

What are the gains with making it proper? It’s fairly level now, at least to the eye… why lower the rear?

I was going on a misconception that you had been working on your suspension and perhaps had installed new springs and such. Though re-reading it I see you did not say that, but have only added the output shaft so are messing with the driveshaft.
But it's not a misconception I don't think to say you are sitting at a higher ride height than would normally be expected. That part is true enough based on your measurements, but the fact that you like it and want to keep it that way is all we need to know now.
The only "gain" then would be to lower it to a more common height and less driveshaft angle. Since that's not what you want at this point, there's no gain to be had.
Yet...
Meaning we only need to revisit it if you have trouble achieving good angularity and performance out of your driveline.

Paul

 

[DirtDonk]

Solving graphically, I get about 12 degrees for diff ujoint difference in angle, and 22 degrees for double cardan at TC difference of angle.

While you do care about the transfer case pinion angle for overall usability, it's not the angle that is taken into account by raising or lowering the rear pinion. As you say, that's the angle that we care about most often because it's the one that is needed to re-adjust for lift.
If you have lifted a Bronco so high that the double-cardan setup at the t-case binds, you have other issues to deal with and in a whole different way.

Pretty sloppy work by me, but within a degree or two.

Not sure what you mean by sloppy work. What else could you have done?
Or did you fabricate your own transfer case cross-member and lift the suspension to the moon?

Need to rotate the diff up, which will also reduce the angle at the double cardan.

What is the angle difference as it sits?

When you say driveshaft was 23 and pinion was 12, if I'm understanding what you're saying, the pinion angle we care about is 23 - 12 which is 11. You want to drive that angle to be roughly 2 degrees below driveshaft angle.

Yep, correct.

Think it should also increase the amount of overlap at the slip joint which is going further in the direction of the concern you noted, I don't know any rules of thumb for that dimension but sure others here do. Doing a suspension stuff would give you a clear answer, but starting with previous knowledge would be good.

Definitely. But in all the years we've discussed it here, I thin it was only once or twice many years ago that anyone actually articulated the suspension to see how much movement the driveshaft went through.
Time we did it again I say!

Just visually, I'm not sure how much the shaft compresses further because even though you are indeed shortening the distance from the t-case as the springs compress, the differential also moves rearward due to the shackle movement. The front pivot point remains static, allowing the springs to pull the diff rearward as they flatten out.
But there is probably motion both ways, so it depends on how much upward vs rearward there is.

Someone with a road-worthy Bronco could take video of the slip joint on the shaft while a bunch of friends pile up on the rear bumper. Then jack it up from the frame to see how much movement of the shaft there is during suspension extension.
Driving around with a camera aimed at the shaft over a bumpy road would be a great bit of video too. I know it's been done, but something more recent and something done with different amounts of lift and modifications would be good to add to the archive.

Any video makers out there want to contribute?

Paul

 

[guidoverduci]

Thanks Paul!! Yes, I’ve been driving on that suspension for a couple years (although not a ton of miles), so ride height is not new.

I will definitely be adjusting the pinion as recommended. I like both options, but I don’t have a welder and don’t know how to weld… so the steel shims sound like the easier solution, just not the most correct.

 

[DirtDonk]

They are definitely easier.
But if you're on the fence ever about this kind of thing, a new spring perch can be "bolted" in place so to speak. Then welded after the fact by someone with the tools and skills.
You simply line them up, put the springs on them and install the u-bolts. While holding everything in it's proper place, you can torque the u-bolts down to hold it all in place long enough to drive to a muffler shop or welding shop to get the final touches done.
Not saying this is optimal, and you'd do well to drive it VERY easily and calmly so as not to twist the axle within the perches before it's welded. But u-bolts when fully torqued can apply a very firm grip on things for the short term.

No personal experience though, and maybe James can comment when he sees this recommendation. If it's not good or smart, he'll let us know. I'm only going on theory because I've never driven a rig with un-welded perches. And I know it's reasonable to assume that they can easily twist up while driving if enough force is applied. But with good strong u-bolt tension I think you could get it to a local shop.
If you're in a more rural area, this might not be an option even if it was workable. But then again, a tractor supply/service company might have a mobile welder that is regularly in your neck of the woods.

I forget where you are, but seems to me you're actually here in one of the metro areas.
Heck, if that's the case then I might be tempted to recommend you take a trip to James' shop!
I only say that from all the other times he's offered his help to local members.

Paul

 

[Steve83]

This is Ford's explanation:

(click this text)

 

[Speedrdr]

This is Ford's explanation:

(click this text)

Holy crap, but that’s a lot of explaining Ford did! Gonna have to sit down and read this over more than once for certain.

Randy

 

[jamesroney]

They are definitely easier.
But if you're on the fence ever about this kind of thing, a new spring perch can be "bolted" in place so to speak. Then welded after the fact by someone with the tools and skills.
You simply line them up, put the springs on them and install the u-bolts. While holding everything in it's proper place, you can torque the u-bolts down to hold it all in place long enough to drive to a muffler shop or welding shop to get the final touches done.
Not saying this is optimal, and you'd do well to drive it VERY easily and calmly so as not to twist the axle within the perches before it's welded. But u-bolts when fully torqued can apply a very firm grip on things for the short term.

No personal experience though, and maybe James can comment when he sees this recommendation. If it's not good or smart, he'll let us know. I'm only going on theory because I've never driven a rig with un-welded perches. And I know it's reasonable to assume that they can easily twist up while driving if enough force is applied. But with good strong u-bolt tension I think you could get it to a local shop.
If you're in a more rural area, this might not be an option even if it was workable. But then again, a tractor supply/service company might have a mobile welder that is regularly in your neck of the woods.

I forget where you are, but seems to me you're actually here in one of the metro areas.
Heck, if that's the case then I might be tempted to recommend you take a trip to James' shop!
I only say that from all the other times he's offered his help to local members.

Paul

Yup. and if you are scared of spinning the axle, just pull the rear driveshaft and move in front wheel drive.

My recommendation to not use wedges is applies if you are going to move the axle back. There are plenty of leaf packs with wedges, and plenty of tapered lift blocks out there. I just don't like doing the job 2x. If you are going to center the axle, and you are going to rotate the pinion, and you are going to have to figure out the angle...then new perches are the way to go.
If someone has already done the work for you, and you know the answer is 6 degrees...then you don't need me.
You will note it the picture below, the FIRST thing to happen is the perches.
But you should know that because of this thread...I had to go build a new Dana 60 for my Bronco. I'm not so happy about that.
And yeah, if someone owns an EB and brings me an axle that needs welding...I'll help.

 

[jamesroney]

Thanks Paul!! Yes, I’ve been driving on that suspension for a couple years (although not a ton of miles), so ride height is not new.

I will definitely be adjusting the pinion as recommended. I like both options, but I don’t have a welder and don’t know how to weld… so the steel shims sound like the easier solution, just not the most correct.

OK, I caught up to you. I don't have any weight on my Bronco, so my 3.5 suspension lift is sitting at 12.5 between axle and frame. So I will cinch it down to 9.5 inches and check the pinion angle. I don't have a transfer case or engine in the chassis. So I will install that and get a measurement. Right now, my pinion is sitting at 15 degrees. I have no idea where you got 23 degrees from. But I think I'm already too high at 15 degrees. I'll have better numbers next week. I did go ahead and drill my perches and plates with the additional hole 1 inch back.

 

[guidoverduci]

OK, I caught up to you. I don't have any weight on my Bronco, so my 3.5 suspension lift is sitting at 12.5 between axle and frame. So I will cinch it down to 9.5 inches and check the pinion angle. I don't have a transfer case or engine in the chassis. So I will install that and get a measurement. Right now, my pinion is sitting at 15 degrees. I have no idea where you got 23 degrees from. But I think I'm already too high at 15 degrees. I'll have better numbers next week. I did go ahead and drill my perches and plates with the additional hole 1 inch back.

Thanks for the info James! My pinion is around 12 when I measure it like your first picture. It’s the driveshaft angle that is 23. I’ve got a couple other things I’m working on getting fixed before I dial in this pinion issue. But currently, it’s running and no issues that I can tell. I might have to drive it down to you and let you give it a once over!