Front Driveline Options/Advice/Help (1 Viewer)

[Dissent]

I used a digital angle cube to determine the angles of my flanges and after zeroing the cube on the concrete garage floor, the front pinion flange is 6.4 degrees and the transfer case flange is 3.2 degrees. When I place the cube on one flange and zero it, then move it to the other flange, it reads a delta of 9.6 degrees which jives with the above numbers.

I removed my front OEM shaft and replaced it with a DC shaft a few weeks ago after lifting my 97 LX450 with TJM 50mm Heavy Linear springs with 30mm Poly Spacers and Slee caster correction plates, attaining a solid 4" lift on all corners, and began experiencing driveline GRRRs in the front. I've had the front end aligned by the dealer with no impact.

I've adjusted the rear pinion/transfer case flanges perfectly parallel using Metal Tech adjustable Lower Control Arms and installed new OEM u-joints then balanced the rear shaft and all vibrations are gone in the rear.

I am left with a vibration in the front between 45-80 which is very noticeable under load. I pulled the front shaft today and measured the angles. A test drive with the front shaft off is glass smooth up to 80 (couldn't go much faster tonight).

I'm not sure what to do. The DC shaft doesn't appear to be parallel to the pinion with 0 degree deflection as required for a DC shaft but the flanges aren't parallel to run an OEM shaft.

What can I do outside of running a part time 2WD kit? I'm literally at my wits end here.

 

[84shortyota]

A driveshaft with regular u-joint flanges is a completely different animal regarding driveline angles vs. a DC shaft. Its my understanding, coming from the mini-truck world, that when using a DC shaft the pinion should be more or less pointing at the t-case flange. As apposed to being parallel with it...just a thought.

 

[bryson]

Have you tried re-phasing the slip end of the shaft? Pull it apart, rotate it 90* and try it again. Mark the original orientation before you pull it apart. In theory this shouldn't necessarily fix your problem, but it can't hurt to try. Some people have reported semi successful results with this on pesky vibes. It may be just enough to work for you.

If that doesn't work, you may be stuck doing a cut and turn on the front knuckles to get your pinion angle where it needs to be while still maintaining appropriate caster angles.

 

[bugsnbikes]

4" lift........id try pulling the poly spacers and see if that changes things........you shouldnt need em to run 315s. (and its an easy mod).

are u running the spacers to correct stinkbug?

 

[bugsnbikes]

if your rear end is waaaaaay high- you could add some weight or cut rear spring 1/4" since you shouldnt need a full 4" spring to run 315s.

if vibes go away after pulling spacers.......you can try 10 or 20mm spacers and then fiddle with castor correction if vibes come back.

id also plan to do washer mod at frame side of control arm to move axle 1/4" foreward as 4" springs plus 30mm spacer has effectively moved your axle back in the wheelwell- not helping the situation

 

[Dissent]

@bryson - I've not tried rephasing the OEM shaft, I need new u-joints and balance first. 9.6 degrees is way off but I'll add it to the list of things to try.

@bugsnbikes - The truck sits level now and I have LCA's in the back and everything is perfect in the rear. I have caster correction plates, isn't the washer mod to accomplish the same result? Removing the 30mm spacer will lower the front but is there a predictable model to determine how much pinion rotation I'll recognize by removing them beforehand? I'm running the spacers to level the truck out, yes.

@84shortyyota - That's my trouble, I'm currently in the world between the OEM and DC shaft with this particular pinion angle. Neither is working.

Is there anything detrimental to running with the center diff locked and the rear shaft only long term? I've got an upcoming 5000 mile trip that I may be forced to run this way.

 

[Dissent]

I just read the post below from another thread. I suppose the goal would then be to return my pinion to -3.2 degrees to match the transfer case +3.2 degrees. This means I'd need to rotate the pinion down 4.2 degrees to achieve the stock broken back configuration. I wonder if removing the 30mm spacers will accomplish this.

"The 80 front driveshaft does not have parallel angles from the factory in stock configuration. It has a broken back configuration like this \-------/ and not /----/. The angles are the same, but they are opposing."

 

[2fpower]

If the vicious coupler is working, you won't be able to park without the ebrake.

DELETE -- have cdl switch to override.

 

[Dissent]

@bugsnbikes - I don't have 4" springs installed anywhere. I have 50mm springs (1.97") and 30mm spacers (1.18") resulting in only 3.15" of lift. The saggy stock springs accounted for the other .85" I suppose.

 

[Dissent]

@2fpower - I don't understand what you mean.

 

[bugsnbikes]

my bad- pull spacers and see what happens.. it should point your tcase down to pinion a few deg.

 

[Dissent]

No problem. I'll pull the front spacers tomorrow and have ordered OEM u-joints for install on the shaft next week. I'll play with the phasing once I get the shaft back but I hope the spacers will make up for the angle issue.

 

[neatus]

@bryson

Is there anything detrimental to running with the center diff locked and the rear shaft only long term? I've got an upcoming 5000 mile trip that I may be forced to run this way.

Do you have the CDL switch mod done? You can run your rig with the center diff locked this way if you have to. I will confess that I ran mine like this with no front shaft for about 3000 miles. No issues.

 

[Dissent]

I do have a CDL, running like that now with the front shaft off.

 

[inkpot]

I do have a CDL, running like that now with the front shaft off.

So why not replace the front DC shaft and go? I thought you liked it earlier in your project to work all this out. Some of us running 4" and 4+" lifts are running stock front shaft and some are running a DC.

 

[Dissent]

Earlier in the project was GRRR in the front with vibration in the OEM shaft. I'm heading back to that with new joints in hopes it was bad joints but the angles don't jive even for the stock shaft. Pulling the spacers tomorrow and will check angles see if its stock shaft friendly.

 

[bryson]

I wasn't necessarily suggesting to re-phase the OEM shaft, but you could certainly try that. I was thinking it was worth a shot to re-phase the new CV shaft.

 

[Delancy]

Unless you've some complicated formula to input the TC centerline angle, your measuring methods sound flawed, if attempting to determine why a DC shaft vibes.

Only NASA has a concrete floor one could claim a bevel box level on, but it's an unnecessary benchmark, anyway.

The only degree that matters is 0° between the centerline of pinion output flange and the driveline, and only way to check is to zero out on a cap that's plumb with the world on diff or driveshaft, rotate shaft 90°, then check other cap (or driveshaft flange...whatever).

For a conventionally joints shaft, the pinion flanges should be the same degree off the centerline of the shaft, be it | | or / / or \ /. As long as they're the same, the shaft rotates in the same circular pattern, which is why Toyota's broke back doesn't vibe.

In that instance, the opinion flanges should be the same angle off an imaginary 90°.

None of this matters, though, because you can't adjust anything, so if you've any condition different than // or || or \ / for conventional shaft, or | _ for DC, say with a

| / or \ | or 2° 6°

Then the best you can hope for is its off enough (think 6°) that a double, double cardan will work.

Simple stuff to gauge, hard as hell to fix correctly, once the variables are known.

 

[Dissent]

@bryson - Gotcha, you can't rephase the DC shaft, it's irrelevant with that design.

 

[Dissent]

@Delancy - How do you know my garage isn't at NASA? I used the concrete as a common reference point once I determined the 9.6* delta. I was referencing each flange to a known "level" to validate the 9.6*. I'm going to pull the spacer tonight which may rotate the pinion back down where the OEM shaft can tolerate it. I'll have the OEM balanced shaft back on Tuesday to test but I'll know the \ / angles tonight for the flanges.

The DC shaft was at about 3* if I recall correctly. The rear DC, before I removed it, was at 1.55 degrees and was really generating some harmonics. The front DC shaft won't work unless I jack the pinion up even higher. DC=Fail on this setup. Should be easy to sell to someone who can use it though. From my research on this forum, I don't think many are absolutely sure of the 90 degree -| relationship required for a DC, I think they just "know" it will work when OEM won't. There's no guarantees in life it turns out.

If I could afford it, I'd put in a part time kit and leave the DC shaft and Spacers in place. I will work towards a part time kit anyway as I'm sure it would be beneficial down the road. In hind sight, I'd start with a part time kit prior to the lift and save myself a lot of front end headaches but then I would've been ignorant of flange relationships and driveshaft angles forever....ignorance is bliss you know.