rear driveshaft angle

[73dreambronco]

I just installed a 3 1/2 " sus lift on my 73 no body lift just new mounts. The rear drive shaft seams to be at a pretty radical angle. What angle is acceptable? The truck rolls freely and the shaft spins freely as well.

thanks,

 

[Bully Bob]

Hay '73,

I just went thru this,... seems none of the suppliers advise about this delema. (Wild Horses catalog touches on it) (My lift was only 2.5" so no mention at all.)

My guess is you'll have vibration. (I did) I went thru this

nightmare "three times" (dis-assemble/assemble) B/4 I got it right. I put in 2deg., then 4deg., then finally 6deg. shims to eliminate the angle/vibration.

On yours, I would start with 6deg. shims. The spring locating pin needs to be removed & spacers added/made to extend them down thru the shim into the spring purch. (C-clamp the leafs together prior to pulling the pin out, or you'll have a real mess.)

I measured a stock Bronco pumpkin & mine after completion & the round part (pinion tube) the yoke slips into is 1" higher. (in relation to the very bottom of the pumpkin) It went from 4" to 5" diff. That's how much the axle rotated with the 6deg. shims.

I wish I'd have measured it from the start, just to see if mine was somehow different from the factory.

BTW, the vibration was around 25-30 MPH .....& again at 55-65 & was a "high frequency" vibration...un-like a wheel problem.

Also, the lift will bring out any imprefections in the drive shaft as well.

HTH,

Bob

 

[S_bolt19]

WH, BC, Duff & others recommend that anything over a 3.5" lift to redirect the axle. Anything 3.5" and lower, they say you can run "stock" angles. I found this out when I originally put my lift on. So, I ran 3.5" leaf springs for almost 10 years with no driveline angle changes. Last winter I went with 4.5" leaf springs and still dont have any problems as far as vibration goes. That is why you have a CV joint on the driveshaft. It takes up the problem of that steep angle. Idealy, if you have the time and the inclination to do it, you should relocate your spring perches. It doesn't have to be perfect, for that matter, you can actually eyeball the angle from pinion gear to x-fer case output shaft and get very close. As long as you point the pinion yolk at the output shaft you will be in good shape.

The only major problem that I have ever had is that the driveshaft wasn't up to par with the new angle and length. Your overall length will be roughly anywhere from 2-4" longer than original. So your old driveshaft will not handle the slip required to have full suspension travel. The original CV joint is most likely not up to ***** either, so I would say replace the driveshaft. Dont have it rebuilt, get a new extended one from someone like Tom Wood Custom Driveshafts.

 

[Broncoholics]

Are you using 3.5" leafs, blocks or add-a-leafs? I didn't have to use shims under mine (10 pack 3.5" leafs). Was thinking of adding a 1/2" shim to get 4" total. With all you guys getting shims did you see any that are 1/2" thick with a 4-6 deg angle?

 

[Bully Bob]

I respectfully disagree..

& so does my driveline shop. :-B

"That is why you have a CV joint on the driveshaft. It takes up the problem of that steep angle"

-----This helps the top but NOT the rear U-joint..!

That angle is un exceptable & ******* the U-joint. (even if it doesn't vibrate)

"Idealy, if you have the time and the inclination to do it, you should relocate your spring perches"

----Isn't this a contradiction..? :huh:

With the shims, & the excessive angle removed, your dr. shaft (length)may be in tolerance...have a drive-line shop varify for sure.

My dr. line shop lengthened my dr. shaft ...he didn't like it & put on a "new" one at no additional charge. That took out the remaining 2 % of vibration.

Smoooooth, all the way up to 80mph now.

"my two cents"

Bob

 

[Bully Bob]

Are you using 3.5" leafs, blocks or add-a-leafs?

 

[S_bolt19]

Bob, I am not contradicting myself in my statement. I said "idealy". By this I mean that you should have the axle rotated and relocate the spring perches, but you dont have to if the means aren't available to you. I didnt do this on my old 3.5" springs or my current 4.5" springs because #1 I didnt have to & #2 I had a different axle that I ended up putting under the 4.5" springs that I had to weld the perches on anyway.

But yeah, you should correct the angle problem before you test it out. 6 degrees is about max for a CV joint. So measure the angle of the output shaft on the x-fer, measure the output on the pinion. If it is within 6 degrees, you are ok, if it is greater than that then you need to shim or redirect the axle.

As for the driveshaft tolerance, any stock driveshaft is too short for a 3" or higher lift. That I have asked a couple of EB shops and found that out the hard way about 10 years ago. I had just put the lift on and my driveshaft bolted up but there was no slip in the driveshaft whatso ever (completely extended). You really need to measure what your current length is (from center of u-joint at the transfer to center of last CV u-joint to center of pinion u-joint) and then pull that driveshaft off and extend it fully and see what your length is. Then put your lift on, stick the driveshaft on and measure again, I bet you come up a couple inches short as far as your travel goes. I had to go with a 36" driveshaft because if memory serves me correct the stock driveshaft is only 32-33" in length. When you are sitting on level ground, your driveshaft should have approx. 2-3" of spline travel left.

This is stuff that very little is said about when you buy the lift. That and extended brake lines, steering angles....then if you put a body lift on.....Well the picture is as clear as mud and no one is there to help you when you need it @-)

 

[Broncoholics]

Jack up the frame and let the axles drop, see if the drivlines turn.

Hey Bull, where are you adding these lock washers for spacers?

Sounds like you are trying to gain space between the perch and the leaf due to the leaf spring center pin being too long with a shim in there?

Any photos? Or maybe explain a bit more. I thought you have to replace the main pin with a longer one so it travels thru the shim and perch in one piece.

 

[Bully Bob]

Hey Bull, where are you adding these lock washers for spacers?Sounds like you are trying to gain space between the perch and the leaf due to the leaf spring center pin being too long with a shim in there?

Any photos? Or maybe explain a bit more. I thought you have to replace the main pin with a longer one so it travels thru the shim and perch in one piece.

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Anything added between the bottom of the spring pac & the perch dis-allows the "pins head" from setting safely into the perch hole...

(spring shops & suppliers have these spacers)

The nut must be removed, & the pin pulled....the spacers go on the threaded end until they butt against the "pin-head"

The spacers must be thin enough (side to side) to pass thru the shim, (wheather flat or tapered) hole. In other-words, the same diameter as the pin-head.

(NOTE; too many spacers & the pin will bottom on the axle tube)

This applies only to "store-bought" shims (they come with a large hole because of the taper) ...if you make your own, the spacers would not be needed.

A small hole in the shim, install the pin thru the shim, then the spring pac & bolt it up. The shim would be part of the spring pac, .... (Jeep does it this way.)

Obviously the spacers are for small adjustments...1/8-1/4 or so. Any large block/shim in there would req. an overall longer pin & installed the "Jeep way"

BTW, the Jeep Rubicons are having vib. problems.....seems with just a 2" lift they are going to a "double" cardian joint (C/V)

I think I said what I mean....? :-"

Bob

 

[ken0275]

Anything added between the bottom of the spring pac & the perch dis-allows the "pins head" from setting safely into the perch hole...(spring shops & suppliers have these spacers)

The nut must be removed, & the pin pulled....the spacers go on the threaded end until they butt against the "pin-head"

The spacers must be thin enough (side to side) to pass thru the shim, (wheather flat or tapered) hole.  In other-words, the same diameter as the pin-head.

(NOTE; too many spacers & the pin will bottom on the axle tube)

This applies only to "store-bought" shims (they come with a large hole because of the taper) ...if you make your own, the spacers would not be needed.

A small hole in the shim, install the pin thru the shim, then the spring pac & bolt it up. The shim would be part of the spring pac, .... (Jeep does it this way.)

Obviously the spacers are for small adjustments...1/8-1/4 or so. Any large block/shim in there would req. an overall longer pin & installed the "Jeep way"

BTW, the Jeep Rubicons are having vib. problems.....seems with just a 2" lift they are going to a "double" cardian joint (C/V)

I think is said what I mean....?  :-"

Bob

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Ok, since I am a novice probably like a lot other readers that come here for info on our obsessions.

I have my 76 Bronco with the auto trans. I purchased the JBG 3 1/2 super flex suspension kit. The kit comes with 11 leaf spring pack.

Do I or don't I need to extend my driveshafts?

If I do need to extend them, what length should they be?

I am racing to get my truck on the road by the end of this month and everyone is going back and forth with what worked for them, but I want my truck done right the 1st time. I don't want to be out on trail and have a drive shaft failure.

If I do need to extend I need to get them into a shop asap, so they will be ready when the truck is done.

I am still hoping to make the jamboree!

:wacko: So stop cornfusing us novices :wacko:

 

[Bully Bob]

Ken,

Sorry for the confusion.....very typical of "over the wire" discussions.

1st, your above quote was of a drive-line/pinion alignment.

2nd, the point I was trying to make, in part, was; There's probably no ONE exact answer...BECAUSE,

1) some driveshafts have already been modified. (for various reasons, who knows)

2) what your usage plans are.

3) what cond. your dr. shaft is in.

Once your veh. is on flat ground, & completely assembled, measure from flat surface on transfer case out-put shaft yoke, to flat on rear diff. yoke. ( this is = to center of u-joint cap to center of u-joint cap)

This will give a drive line shop the info. needed to tell you what length your dr. shaft should be.

BUT...if you intend to, (or have to) shim & tilt your axle/pinion up that measurement is obsolete. (& there goes your "new" dr. shaft correctness)

Like Bolt19 said... " these guys (lift suppliers) let you fly on your own, not offering up the pit-falls that come with a lift" ....might not sell as many if they did.

You'll be fine....assemble everything, LOOK at the dr.shaft angle at the rear diff. IF you don't like it, shim the axle...THEN do the dr.shaft mods (or a new one)

 

[ken0275]

Ken,Sorry for the confusion.....very typical of "over the wire" discussions.

1st, your above quote was of a drive-line/pinion alignment.

2nd, the point I was trying to make, in part, was;  There's probably no ONE exact answer...BECAUSE,

1) some driveshafts have already been modified. (for various reasons, who knows)

2) what your usage plans are.

3) what cond. your dr. shaft is in.

Once your veh. is on flat ground, & completely assembled, measure from flat surface on transfer case out-put shaft yoke, to flat on rear diff. yoke. ( this is = to center of u-joint cap to center of u-joint cap)

This will give a drive line shop the info. needed to tell you what length your dr. shaft should be.

BUT...if you intend to, (or have to) shim & tilt your axle/pinion up that measurement is obsolete. (& there goes your "new" dr. shaft correctness)

Like Bolt19 said... " these guys (lift suppliers) let you fly on your own, not offering up the pit-falls that come with a lift" ....might not sell as many if they did.

You'll be fine....assemble everything, LOOK at the dr.shaft angle at the rear diff. IF you don't like it, shim the axle...THEN do the dr.shaft mods (or a new one)

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I know all about being left to fly on my own.

I spent 1300 bucks for the lift kit and steering conversion kit to make it pre-76 at JBG I asked if there was detailed instructions included in the kit.

The guys answer was "If you can figure out how to take it apart, you can figure out how to put it back together"

All I can say is buy stock in Miller Lite Company.......I am going to be doing a lot of head scratching and beer drinking this month, trying to get this done.

 

[Bully Bob]

I know all about being left to fly on my own.I spent 1300 bucks for the lift kit and steering conversion kit to make it pre-76 at JBG I asked if there was detailed instructions included in the kit.

The guys answer was "If you can figure out how to take it apart, you can figure out how to put it back together"

All I can say is buy stock in Miller Lite Company.......I am going to be doing a lot of head scratching and beer drinking this month, trying to get this done.

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Same here...my $650 lift quickly became $1000

The only knowledgeable folks ARE us diehards who have done these lifts, & of course, the EB speciality houses.

One problem is each of these rigs have their own "idiosyncrasys" (diff. factories, previous owners,etc.)

Here's some tips that come to mind;

REAR

1) the springs have a front & back

2) the spring ctr. eyelets are stamped & the bolt won't go thru both directions due to a ridge..check & relieve that ridge or you'll have to stop assy., remove spring & start over. (Because you won't remember which way the bolt goes thru 'til you get there)

3) the bolts on the rear shackle (top bolts) must go back the same direction they're in now. If reversed, the large nut & bolt tip will catch on the frame/hangar bracket.

4) if you do 1 side at a time, the axle won't rotate on you.

5) good chance you'll have to seperate spring & axle again (remove u-bolts) to install the tapered shims....but you'll be an expert by then (I can swap shims in 15 min. per wheel now..!)

6) "GOOD" jack stands are a "MUST" (no crushed limbs) & a come-a-long is great.

7) longer rubber brake line (should be in kit) needed.

FRONT

1) I did one side at a time...so the truck (frame) must be level & the axle must be level. This allows the radius arms to remain parallel. All those pieces must go back exactly as they came off. The arms & caps are a matched set & stamped on top. (this is assuming no one else did this job wrong before) The C-bushings go in only one way...they're marked on the inside. Cross rotate while tightening the bushing caps to prevent torqueing up or down.

2) your kit should (I would think) have an adj. track bar, track bar drop bracket, & dropped pitman arm.

3) you can pull the whole axle out to install the C-bushings on both sides at once if you prefer.

Took me two "slow & go" days to do the front...(eyeballing & memorizing things)

Could prob. do another in one day now easily. I had no helper... a helper would be nice if you're "both on the same page."

My guess is they give NO instructions for lawsuit reasons...

As stated earlier, dr. shaft issues would be last, after decision on shims, to remove angle at rear dr. shaft/pumpkin

HTH,

Bob

 

[SaddleUp]

Hmm... I don't see any replies above that really address it fully so here is what I have to add. First the lift kits will sometimes throw the angle off at the rear u-joint but it depends on the springs being used. Some of them already have some angle built into them so one person can lift theirs 3 1/2" and be fine while the next can't. Because of this there is no right answer as to what will be needed for everyone. As to the correct angle the rear u-joint should be approx. 1 or 2 degrees below the driveline centerline. If it is straight at the transfer case then the needle bearings in the u-joints will not move and will then dry up and go bad. If it is excessive then it will create a vibration that will quickly destroy the u-joint. The vibration it creates is fairly distinct because it will change as you accelerate or decelerate. This is because the angle changes slightly when you do. One way to get a close measurement is to simply put the rear yoke vertical and then measure from the center of the t-case yoke to the top cap and then the bottom cap on the lower u-joint. Try for about 1/16" longer to the bottom one which will get it pretty close. 1/8" may be okay but any more will cause problems and require shimming or new perches. As was mentioned above the CV joint is to deal with a bad angle at one end only. In reality you can have steeper angles on drivelines without CV joints but they need to have matching angles both top and bottom so you can't get as much height difference with them because the pinion is horizontal with the drivetrain instead of being pointed more or less straight at it.

 

[bigjake]

Ok, since I am a novice probably like a lot other readers that come here for info on our obsessions.I have my 76 Bronco with the auto trans.  I purchased the JBG 3 1/2 super flex suspension kit.  The kit comes with 11 leaf spring pack. 

Do I or don't I need to extend my driveshafts?

If I do need to extend them, what length should they be?

I am racing to get my truck on the road by the end of this month and everyone is going back and forth with what worked for them, but I want my truck done right the 1st time.  I don't want to be out on trail and have a drive shaft  failure.

If I do need to extend I need to get them into a shop asap, so they will be ready when the truck is done.

I am still hoping to make the jamboree!

:wacko: So stop cornfusing us novices :wacko:

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Ken,

I've got the same lift as you for a '69 302 3 speed and I'm stuck from going further until I figure this ************* out. What was your final outcome with the shim and driveshaft?

And... Can someone tell me what the spacers that you have mentioned are for? I've noticed that the post from the leaf that is supposed to seat nicely in the perch is too fat and there's about a 1/8" gap between the two (that's after I took a 4lb sledge to it). Is that what we're talking about using the spacer for?

 

[Bandit]

Ok, since I am a novice probably like a lot other readers that come here for info on our obsessions.I have my 76 Bronco with the auto trans.  I purchased the JBG 3 1/2 super flex suspension kit.  The kit comes with 11 leaf spring pack. 

Do I or don't I need to extend my driveshafts?

If I do need to extend them, what length should they be?

I am racing to get my truck on the road by the end of this month and everyone is going back and forth with what worked for them, but I want my truck done right the 1st time.  I don't want to be out on trail and have a drive shaft  failure.

If I do need to extend I need to get them into a shop asap, so they will be ready when the truck is done.

I am still hoping to make the jamboree!

:wacko: So stop cornfusing us novices :wacko:

24672[/snapback]

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&lt

What you have to worry about is the spline slipping out of the yoke,When I installed my 3and 1/2 lift I left the stock driveshaft on ,it was fine until I was doing some extreme articulation and it popped out of the yoke.If you measure the distance from output shaft on the transfer case to the yoke on the rear end,any driveshaft shop or Bronco specialist can tell you what size would be Ideal.Any time you lift your Broncos suspension,you are moving that much further out of the yoke.Ideally every suspension lift needs a longer shaft.The newer heavyduty driveshafts seem to have a much longer splined area to keep contact.As far as driveline angles,are there guys out there running 3and 1/2 lifts with out changing angles?sure...a bunch I bet.....propably for years without a whole bunch of problems.Is it Ideal ..**** no....when I recently installed a 4 and 1/2 inch ...I had the drive line shaft weld new spring perches in and it was perfect,we kind of eye balled the suspension at rest and decided on where to weld em.All of those shims an blocks cause axle wrap to exagerate,and can be dangerous,you put enough horsepower,get enough axlewrap from homemade blocks..your truck can start spittin things out!Any one with any sense knows that the Ideal set up is the axle directly on the spring perch,bolted up tight...you cant always do everything,all the time ...but it doesnt cost that much to have a competent shop do it right .

BANDIT awesome '73.

&lt

 

[Bandit]

Ok, since I am a novice probably like a lot other readers that come here for info on our obsessions.I have my 76 Bronco with the auto trans.  I purchased the JBG 3 1/2 super flex suspension kit.  The kit comes with 11 leaf spring pack. 

Do I or don't I need to extend my driveshafts?

If I do need to extend them, what length should they be?

I am racing to get my truck on the road by the end of this month and everyone is going back and forth with what worked for them, but I want my truck done right the 1st time.  I don't want to be out on trail and have a drive shaft  failure.

If I do need to extend I need to get them into a shop asap, so they will be ready when the truck is done.

I am still hoping to make the jamboree!

:wacko: So stop cornfusing us novices :wacko:

24672[/snapback]

​

&lt

What you have to worry about is the spline slipping out of the yoke,When I installed my 3and 1/2 lift I left the stock driveshaft on ,it was fine until I was doing some extreme articulation and it popped out of the yoke.If you measure the distance from output shaft on the transfer case to the yoke on the rear end,any driveshaft shop or Bronco specialist can tell you what size would be Ideal.Any time you lift your Broncos suspension,you are moving that much further out of the yoke.Ideally every suspension lift needs a longer shaft.The newer heavyduty driveshafts seem to have a much longer splined area to keep contact.As far as driveline angles,are there guys out there running 3and 1/2 lifts with out changing angles?sure...a bunch I bet.....propably for years without a whole bunch of problems.Is it Ideal ..**** no....when I recently installed a 4 and 1/2 inch ...I had the drive line shop weld new spring perches in and it was perfect,we kind of eye balled the suspension at rest and decided on where to weld em.All of those shims an blocks cause axle wrap to exagerate,and can be dangerous,you put enough horsepower,get enough axlewrap from homemade blocks..your truck can start spittin things out!Any one with any sense knows that the Ideal set up is the axle directly on the spring perch,bolted up tight...you cant always do everything,all the time ...but it doesnt cost that much to have a competent shop do it right .

BANDIT awesome '73.

&lt

 

[DMichael5]

Ken,

The answer is an absolute maybe....If you have started the lift you will not know until you install the drive shaft. If I was doing the lift I would just call a local drive line shop...tell them the lift height and truck specs...They should be able to work the math and figure it out.It seems to me that with you wanting the truck on the road in a few weeks that having the DS taken care of sooner than later makes sense just to ensure no problems on the trip. What did JBG recomend...have you tried calling them back and asking them? One thing for sure if that is the service that they normally give then I will buy my stuff elsewhere.

Good LucK

DM