Rear Driveshaft Angles/Symptoms w/6" Lift (1 Viewer)

[jellis]

I've done a bit of searching but thought I would do a quick post and see what people's thoughts were. I've got an HDJ81 with a 6" lift and since I bought it a year ago the rear output bearing on the TC has become loose AND the output seal on the rear diff has started leaking. This does not strike me as coincidental. I want to verify any potential causes prior to fixing what might just be symptoms!

I measured my angles with my phone, my rear TC is at 2.6 degrees, the shaft at 12.0 degrees, and the rear pinion is at 4.3 degrees. That gives me operating angles of 9.4 degrees at the TC and 7.7 degrees at the pinion, the total difference is 1.7 degrees. So it's a bit higher than the ideal of 1 degree difference (due to acceleration forces pointing the pinion up), but not crazy-bad.

Is this 0.7 degrees out of spec enough to cause these issues? Also to complicate matters greatly, I realized in the process of measuring my angles that my rear shaft was assembled OUT OF PHASE for some reason (as in, really SUPER bad out....30-45 degrees). I believe that this itself might have played a much larger role than the angle offset in causing these issues.
I currently have a slight vibe at highway speeds (even after putting the shaft in phase). But due to the loose bearing it's impossible to know what's causing what now--and I don't remember when the vibe it started. There did used to be a weird buzz during acceleration at a specific (narrow) RPM which I attributed to an exhaust rattle (because it sounded like a loose piece of sheet metal rattling under the rear of the car). However, that has randomly disappeared for some reason. Perhaps that was actually my driveline prior to the bearing getting loose?!? Can they get THAT loud?!?

I have non-adjustable arms in the rear on both the LCA and UCA. I think I should get adjustable UCA's and slightly adjust the angle prior to fixing the loose bearing/leaks. A rear DC driveshaft (and even double DC shaft) is also an option and has helped other folks. Seems expensive, but so is fixing the bearing and leak!

Any thoughts/advice are much appreciated!

 

[cybrstar]

Cut 3/8 of an inch on your upper control arm and reinforce. Fixed my pinion angle with a 6 inch lift.

 

[jellis]

I'm assuming these are not my stock arms since they are not adjustable but close to where they should be. EDIT: I originally posted that my UCAs needed lengthened to adjust the angle correctly but I just checked and they do in fact need shortened, cutting and sleeving them would be fairly straightforward.

Another quick question: How much DS yoke slip do you have available at standard ride height? My front is fully compressed (so much so that I cannot even get it on/off without jacking up the body) which is SUPER not good on anything, my rear has very little and I suspect might be compressing to full retraction during articulation/bumps. That could also cause bearing/seal issues! They both might need shortened? Just curious what's ideal with this big of a lift.

 

[Cruzilla]

Your rear pinion angle should be 1* below transfer case output shaft angle to account for pinion lift under hard acceleration.

 

[greentruck]

I've done a bit of searching but thought I would do a quick post and see what people's thoughts were. I've got an HDJ81 with a 6" lift and since I bought it a year ago the rear output bearing on the TC has become loose AND the output seal on the rear diff has started leaking. This does not strike me as coincidental. I want to verify any potential causes prior to fixing what might just be symptoms!

I measured my angles with my phone, my rear TC is at 2.6 degrees, the shaft at 12.0 degrees, and the rear pinion is at 4.3 degrees. That gives me operating angles of 9.4 degrees at the TC and 7.7 degrees at the pinion, the total difference is 1.7 degrees. So it's a bit higher than the ideal of 1 degree difference (due to acceleration forces pointing the pinion up), but not crazy-bad.

Is this 0.7 degrees out of spec enough to cause these issues? Also to complicate matters greatly, I realized in the process of measuring my angles that my rear shaft was assembled OUT OF PHASE for some reason (as in, really SUPER bad out....30-45 degrees). I believe that this itself might have played a much larger role than the angle offset in causing these issues...SNIP!

I think you've got some issues going on here. You may want to check with these folks (right there in Utah, BTW.
Tom Wood's Custom Drive Shafts - Toyota Application

A friend has a 6" Slee lift and he has Tom Woods shafts on it. The PO forgot that double cardans need the center bearing greased, too. Tom Woods turned the shaft around quickly at a very reasonable cost and problem solved (weird vibrations, etc).

 

[blahblahblah]

I think you've got some issues going on here. You may want to check with these folks (right there in Utah, BTW.
Tom Wood's Custom Drive Shafts - Toyota Application

I've got a 6" Ironman lift and recently put a Tom Woods DC shaft on it. I ordered it late on a Friday and had it by Tuesday. Not bad for over a weekend.

 

[RFB]

I'm assuming these are not my stock arms since they are not adjustable but close to where they should be. EDIT: I originally posted that my UCAs needed lengthened to adjust the angle correctly but I just checked and they do in fact need shortened, cutting and sleeving them would be fairly straightforward.

Another quick question: How much DS yoke slip do you have available at standard ride height? My front is fully compressed (so much so that I cannot even get it on/off without jacking up the body) which is SUPER not good on anything, my rear has very little and I suspect might be compressing to full retraction during articulation/bumps. That could also cause bearing/seal issues! They both might need shortened? Just curious what's ideal with this big of a lift.

I just left my driveshaft shop an hour ago I have a 6in lift and hes making my new OEM rear DS an 1 longer so ill have an 1in of reveal on my slip yoke, and hes also retubing a new double cardon off a taco, I got sick of buying used DC DS that have been tubed and painted went the whole way this time round.

 

[Oscar Witte]

I have been running stock shaft on 6" lift with no problems up to 80mph

 

[RFB]

I have been running stock shaft on 6" lift with no problems up to 80mph

NICE

 

[RFB]

I have been running stock shaft on 6" lift with no problems up to 80mph

Im guessing every man has his own definition of no problems. Myself I drive my truck a lot 50K a year on and off road and when on road she gives no vibrations rattles etc and if she does I consider it a problem.

 

[cybrstar]

Yup, stock rear driveshaft here too on a 6 inch lift.

Front is a different story. Had to go dc dis from Tatton’s driveline in Utah. Guys name is Curtis and had my driveline to me in a week. Great company and driveshaft in my opinion.

 

[jellis]

Well, there doesn't seem to be much consensus, some rigs need a DC rear shaft and some don't at 6" lift to be vibration free.

I find it incredibly odd that my rear output bearing and pinion seal went out at the same time. I definitely see them as symptoms and not problems per se. And I really don't want to fix these issues and have them reappear in a year or two (or less)!

This would be a more straightforward diagnosis if the rear driveshaft wasn't bizarrely out of phase the entire time I've owned the rig. Based upon the demonstration in this video, an out of phase driveshaft behaves nearly identical to a driveshaft with very wonky (non-equal) operating angles. That said, it's impossible to know if my current geometry is "good enough" to prevent these problems from recurring because an out of phase shaft can wreak havoc.

I think at this point I'll start with fixing the main symptom (loose rear output bearing in the transfer) that's likely causing the current vibrations and see how things change. If there is still vibration of any kind I will probably jump to a DC rear shaft and alter the pinion angle accordingly.

 

[blahblahblah]

Well, there doesn't seem to be much consensus, some rigs need a DC rear shaft and some don't at 6" lift to be vibration free.

I don't know that I actually needed a DC shaft, but my stock shaft had worn splines and was making a lot of noise when it wasn't under load.

Since I already had 4x adjustable CAs on the rear, I figured a DC shaft was a safer bet.

 

[jcardona1]

This would be a more straightforward diagnosis if the rear driveshaft wasn't bizarrely out of phase the entire time I've owned the rig.

Have you fixed the phasing? Take a look at my older thread. I had the same problem. Never touched my rear driveshaft and assumed it was installed correctly. Then one day after installing slightly taller lift springs the horrible vibrations started. I automatically assumed it was the angles. Turns out it was the phasing. It was out of phase the whole time but didn't cause any issues until I went taller.

Rear driveshaft has a serious case of the GRRRRs. What to check next?

 

[Duplex Dave]

That link to the video you posted was awesome! Now I understand the phase issue a drive shaft can have. Hooray for visual aids!

 

[baldilocks]

@jellis, Your driveline is at a 12 degree angle and your output and input flanges are not close enough to parallel. It’s not rocket science but we will mull it over and over looking for anyway to not spend the money on a DC shaft. I’ve been there.

I battled rear driveline growls on deceleration once my lift got to about 5”-5.5”. The very capable and experienced driveline shop I had worked with for many years told me that once that shaft is angled greater than 6 degrees, to expect problems and the steeper the the angle the harder it will be to get the shaft to run smoothly.

I let them build me a rear DC shaft, I rocked the pinion up and it’s been bliss ever since. I have read where some have actually rotated the rear pinion downward, post lift, in order to match the angle of the T-case output. This does two things I don’t want: It increases the angle even more and it puts the pinion closer to destructive obstacles called rocks.

 

[landtank]

the one issue with running a DC shaft in the rear is when your ride height changes you could develope vibrations. So running the truck loaded with gear will require a different pinion angle than running empty to acheive ideal alignment for a DC shaft.

Whether or not its an issue depends on how much change in ride height there is between the two situations.

 

[greentruck]

the one issue with running a DC shaft in the rear is when your ride height changes you could develope vibrations. So running the truck loaded with gear will require a different pinion angle than running empty to acheive ideal alignment for a DC shaft.

Whether or not its an issue depends on how much change in ride height there is between the two situations.

One solution with this can be rear air bags. Not everyone likes 'em, but they do the trick pretty well of keeping ride height from getting too far from nominal. Towing is another factor that air bags can help with. Put both ride height variance from the truck's load and a trailer's drawbar weight loading together and you really gotta do something on a coil-sprung vehicle. Don't know if stock height vehicles exceed the magic 6 degree number at the loaded extreme but I suspect they'd have to be getting close enough you'd want to do something to avoid excessive wear and tear if this was a typical load, rather than an every once in awhile load.

 

[Jgrauman]

@jellis, Your driveline is at a 12 degree angle and your output and input flanges are not close enough to parallel. It’s not rocket science but we will mull it over and over looking for anyway to not spend the money on a DC shaft. I’ve been there.

I battled rear driveline growls on deceleration once my lift got to about 5”-5.5”. The very capable and experienced driveline shop I had worked with for many years told me that once that shaft is angled greater than 6 degrees, to expect problems and the steeper the the angle the harder it will be to get the shaft to run smoothly.

I let them build me a rear DC shaft, I rocked the pinion up and it’s been bliss ever since. I have read where some have actually rotated the rear pinion downward, post lift, in order to match the angle of the T-case output. This does two things I don’t want: It increases the angle even more and it puts the pinion closer to destructive obstacles called rocks.

When you changed the pinion angle did you change the spring purch as well or was it fine with that much angle ?

 

[baldilocks]

When you changed the pinion angle did you change the spring purch as well or was it fine with that much angle ?

I debated moving the spring perch but I debated it long enough to figure out that, even with the increased bow in the rear springs, the suspension performed just as well. I run Slee 4” heavy progressives. I have no clue about how other coils might react. A couple years after rotating the pinion up I had to remove the springs and they stood up straight so the bow did not become permanent.