Atlas install issues and questions

I apologize in advance for the long post. I'm just trying to be thorough with the details.

Rig has a 351W based motor installed with WH Extreme Duty Motor Mounts, C4, Atlas with HD short output and cable shifters. Duff Long Arms and 3.5" lift with coils in the rear (4.25° built-in caster). 4° bushings for a total of 8.25° caster. Rig is mainly driven hard on the sand. Not much street use other than short trips.

I had everything mocked-up this morning and just prior to tear-down I wanted to check drive shafts for binding while cycling the suspension without springs. Also wanted to measure for limiting straps. Rear went great no binding at 18.75" between frame and top of axle. Didn't take any pics after installing the shaft (needs shortened even with the short output shaft, though). Will be ordering new shafts with full splines.



Front I ran into a couple issues. First, I had the transfer clocked up to almost touching the frame. Actually had to remove the Long Arm bolts to get it clocked where I had it. I clocked it at this angle (third hole of four on the clocking ring) to clear the cable shifter assy that mounts on the transfer case. Here's a pic showing the shifter mount and how nicely it fits at this angle.



Installed the shaft to check for binding and it will not really even fit at this angle with 13.25" between frame and top of axle. That's only around 2.75" of droop from ride height (7" + 3.5" = 10.5" at ride height). I still have something like 3.25" more droop left in the shocks. I noticed while working on this problem that my rear output angles down and the front angles up. So I installed my new WH transfer case bushings that were around 5/16" taller than the ones I had installed and this is not enough to make the output shafts be plumb. Is it possible this angle is because the WH motor mounts put the engine slightly higher (around 1")?

So I clocked the transfer case down to position #1 to try to give the front shaft relief and my cable shifter mount interferes with the crossmember. I would have to go back to position #3 to clear the crossmember with the cable shifter mount like it was but that complicates the front driveshaft angle issue.

This pic is of the front shaft binding with 13.25" between frame and top of axle. Looks like I don't have much down travel. I can't install the shaft as it's too short.



This pic shows how the cable shifter mount (not installed) will interfere with the crossmember (yes I will un-modify it).



A few questions.


I'm feeling the pressure as I need to keep moving forward because I need to have it done before the first part of July for our annual trip to Silver Lake Sand Dunes. I pulled the body after January first of this year and everything has gone pretty well until today.

Thanks in advance.

Craig

That sucks. I don't have an answer for you as I'm not running the same combo. Mine is a 4r70w/atlas with a ZF crossmember. I have mine clocked at the first position you tried with the TC almost touching the frame. I wouldn't want it clocked any further down and hanging too far below the frame. I hope someone has an answer for you.

I have the same set up, even the cable shifters. Mine is clocked on the third hole, with the TC about a fingers width from the frame. My Atlas sits at a 5.75* slope rearward, so the front output shaft is pointed up as it come out of the case. I don't have the binding issues that your'e having, my front end is pushed 1". Driveshaft is a little bit longer, using 1310's. My front driveshaft is 14* angle at ride height.



Mark

Nightstick said:

That sucks. I don't have an answer for you as I'm not running the same combo. Mine is a 4r70w/atlas with a ZF crossmember. I have mine clocked at the first position you tried with the TC almost touching the frame. I wouldn't want it clocked any further down and hanging too far below the frame. I hope someone has an answer for you.

Click to expand...

Thank-you.

garberz said:

I have the same set up, even the cable shifters. Mine is clocked on the third hole, with the TC about a fingers width from the frame. My Atlas sits at a 5.75* slope rearward, so the front output shaft is pointed up as it come out of the case. I don't have the binding issues that your'e having, my front end is pushed 1". Driveshaft is a little bit longer, using 1310's. My front driveshaft is 14* angle at ride height.



Mark

Click to expand...

I think my transfer case is sloped just about the same. I'm not stretched on the front. I've got to get this figured-out.

I keep thinking maybe the frame is just that much higher than it will be at ride height with the body on. I just realized that the shock I measured to come up with 6" of travel left was a rear shock and I'm pretty sure they are longer than the fronts. I've got a little work to do pulling and measuring a front shock. But I still think I will have binding at droop with the body on.

Thanks,

Craig

Do you have the stock low pinion front axle? You might have to sacrifice some caster to get to get less binding from the driveshaft.

Thanks Desert Thrasher.

Yes. Low pinion 44. Running 8.25° caster. Should I go with more caster than that?

8.25 is more than most broncos could ever dream of. I'm saying you might have to go with less to keep your driveshaft from binding

5001craig said:

Thanks Desert Thrasher.

Yes. Low pinion 44. Running 8.25° caster. Should I go with more caster than that?

Click to expand...

That's not entirely correct. Duff arms with 4.25* of caster, plus 4* "C" bushings will add up to 8.25*, but that's not your actual caster. You'll still need to have it measured to get an accurate number. Duff long arms and 4* bushings, I'll bet you're still around 4* of caster. It's tough to get more than that because the pinion won't allow it. That's why the best solution is to cut and turn the yokes.

Mark

Did you grind the yokes on the CV any? There is usually casting that can be taken off to eliminate bind.

Thanks for the correction guys on the caster. I would have thought the numbers were added together.

I measured my front shock and it looks like I have around 3" of droop left and not 6. The front shock bodies are longer than the rears but have less travel. I wouldn't have guessed.

Today I called a drive shaft manufacturer I see referenced here on the forum and discussed everything I have going on. He was very helpful and based on the measurements I gave him he can get 32° on the front when he grinds for clearance and I have 27° now. This additional 5° will net around 2.5" of additional droop. I'm getting close.

Incidentally, I shimmed the t-case up .25" thinking this would help the front output shaft angle. It didn't do anything I could see. The guy I talked to today said any benefits in output angle by raising the t-case are almost directly offset by the additional height of the shims.

May try some 7° bushings if they will work alignment-wise. I think they would help get the pinion higher.

Garberz: Can you provide any details on your driveshaft? Not length--did you have it built? Is the CV ground for clearance? Also, have you measured frame to axle at full droop?

Thanks all.

If you're running 4.25 degree bushings now and running into binding issues 7 degree will just make it worse. The higher degree rotates the pinion down not up. Good for caster bad for the pinion angle.

66broncoCT said:

If you're running 4.25 degree bushings now and running into binding issues 7 degree will just make it worse. The higher degree rotates the pinion down not up. Good for caster bad for the pinion angle.

Click to expand...

This is why I read a lot more than I post. Lol

Makes sense now. Thank-you.

5001craig said:

......Garberz: Can you provide any details on your driveshaft? Not length--did you have it built? Is the CV ground for clearance? Also, have you measured frame to axle at full droop?

Thanks all.

Click to expand...

My drive shaft is just a temporary, cobbled together, kind of wore out mixture of parts. Stock length front drive shaft, with a stock rear slip, to make up 2" of length. It's not ground for clearance. I know it binds at 27-28*, but my steering linkage binds before I get that much angle on the drive shaft. I don't have a full droop measurement written down right now. I'm working on a HP44, I'll get a permanent shaft made up then.

Two things that are different between ours. I'm running 2* "C" bushings to raise the pinion up. I offset the loss in caster by installing 1 1/2* eccentric ball joint sleeves. So our caster numbers should be close to the same. The other difference is my Duff arms are mounted 1" forward from their spec location. That difference may have a small effect in the drive shaft geometry, throughout the range of travel. The distance from the CV to the radius arm pivots is 1" less.

Mark

Most people with 4" of lift or greater and the stock Dana 44 will experience driveshaft binding.
You can either swap to a high pinion 44, or just get a high angle drive shaft.
Wild horses sells a nice one.

Unfortunately you have a few things working against you

1) The extreme motor mounts push the engine up increase driveline angle. Good for the rear driveshaft, really bad for the front.

2) The C4 is very short. An overdrive trans or 4-speed Atlas would push things back and help with driveshaft angles

3) The low pinion D44 forces the driveshaft to reach further down.


Solutions:

1) Ditch the extreme mounts and go back to conventional mounts or cut the brackets off the frame and lower them. This may be a double-edge sword though. I have a 351W with extreme mounts and 3.5 inches of suspension lift. With 6" of uptravel from static ride height, I nearly hit the oil pan and mine is very neatly package.

2) Get an overdrive trans like a 4R70W or ZF5. OR swap the Atlas for a 4-speed unit.

3a) Swap the low pinion 44 for a high pinion. I run an stock 78-79 Bronco high pinion 44, zf5 and Atlas. Atlas is clocked nearly touching the frame. Pinion angle is PERFECT. I frequently forget to unlock the hubs and will drive for weeks on the interstate at 75mph without noticing the front end is turning.

3b) Cut the C-forgings loose and rotate them to improve pinion angle while maintaining caster.

3c) This has limited adjustment, but you can buy 1.5° offset ball joint sleeves and add all the adjustment in the Caster direction, then install 2° C-bushings. This will maintain caster while kicking the pinion up 2 degrees.

Thanks a ton for the help guys.

Right now I'm on a deadline and I'm thinking I will stay with what I have and limit droop with straps. I really won't be missing too much droop and it might work ok. I'm thinking I will look for a high pinion 44. Or go with a 9 inch center/60 outers like I wanted to go with but couldn't justify the $$. If I remember correctly, it was close to 6 grand.

I was planning to do discs/gears/locker in my present 44 and hate to put that money into my 44 if I'm going to go a different direction (that's around $1500).

Decisions, decisions... Any thoughts?

If you go with a HP44 down the road, your disc brakes and locker will still be compatible. You'd just need a R&P set, plus an install kit.

Mark

I assume since you sprung for an Atlas that you're going to wheel it. I'd go straight D60 and never look back.

5001craig said:

I apologize in advance for the long post. I'm just trying to be thorough with the details.

Rig has a 351W based motor installed with WH Extreme Duty Motor Mounts, C4, Atlas with HD short output and cable shifters. Duff Long Arms and 3.5" lift with coils in the rear (4.25° built-in caster). 4° bushings for a total of 8.25° caster. Rig is mainly driven hard on the sand. Not much street use other than short trips.

I had everything mocked-up this morning and just prior to tear-down I wanted to check drive shafts for binding while cycling the suspension without springs. Also wanted to measure for limiting straps. Rear went great no binding at 18.75" between frame and top of axle. Didn't take any pics after installing the shaft (needs shortened even with the short output shaft, though). Will be ordering new shafts with full splines.

Front I ran into a couple issues. First, I had the transfer clocked up to almost touching the frame. Actually had to remove the Long Arm bolts to get it clocked where I had it. I clocked it at this angle (third hole of four on the clocking ring) to clear the cable shifter assy that mounts on the transfer case. Here's a pic showing the shifter mount and how nicely it fits at this angle.

Installed the shaft to check for binding and it will not really even fit at this angle with 13.25" between frame and top of axle. That's only around 2.75" of droop from ride height (7" + 3.5" = 10.5" at ride height). I still have something like 3.25" more droop left in the shocks. I noticed while working on this problem that my rear output angles down and the front angles up. So I installed my new WH transfer case bushings that were around 5/16" taller than the ones I had installed and this is not enough to make the output shafts be plumb. Is it possible this angle is because the WH motor mounts put the engine slightly higher (around 1")?

So I clocked the transfer case down to position #1 to try to give the front shaft relief and my cable shifter mount interferes with the crossmember. I would have to go back to position #3 to clear the crossmember with the cable shifter mount like it was but that complicates the front driveshaft angle issue.

This pic is of the front shaft binding with 13.25" between frame and top of axle. Looks like I don't have much down travel. I can't install the shaft as it's too short.

This pic shows how the cable shifter mount (not installed) will interfere with the crossmember (yes I will un-modify it).

A few questions.

Am I looking at something more than a magic shaft? I am running an engine with some power (415 hp/430-450 ft. pounds) and don't want anything to break.

Am I missing something that makes the transfer case lower than it should be compounding the front shaft problem?

What have others done with the crossmember interfering with the cable shifter mount? I did some searching and see where others have made a new crossmember mainly for four-speeds.​

I'm feeling the pressure as I need to keep moving forward because I need to have it done before the first part of July for our annual trip to Silver Lake Sand Dunes. I pulled the body after January first of this year and everything has gone pretty well until today.

Thanks in advance.

Craig

Click to expand...

Hey i had a quick question for you. What size spacer are you running on your atlas input to clear the crossmember??

orygunbou71 said:

Hey i had a quick question for you. What size spacer are you running on your atlas input to clear the crossmember??

Click to expand...

There is no spacer. What looks like a spacer is the clocking ring that comes with the Atlas. Here's a better picture: