CB drop "transmission to CB" angle.

Hello Forum,

I've seen quite a bit of threads regarding diff to CB angles but what about CB to transmission angles?

In my particular case, I once added 2 Toytec CB drop kits (a hair under 3/4"'s) & my driveshaft hummed between 55 & 65mph. I ended up using just 1 CB drop kit & chose to live with the slight take-off vibe and light shudder between 18 & 25. The shudder isn't constant, which I find odd.

Anyway, I'm curious to know if anyone here has had issues with dropping the CB too much. For example, Beefed Taco's CB drop (1").

Thank you

 

nothing you can really do to drop the rear of the trans/transfer case.

the vibration at 55-65 you expierenced with the thicker drop bracket was likely due to the fact that the center joint was close to 0* and the front and rear were at similar opposing angles which is a proper way to setup driveline angles... IF the front and rear u joints were phased right... unfortunatly the stock shaft with the above setup is 90* out of phase and thus you get that vibe at those speeds.

I definietly went through the same thing as you (using washers and some aluminum blocks) ended up at ~1/2 an inch of drop... least ammount of cruising vibes and least amount of take off vibes... beyond that not much i can do.

I do have a suspicion take off vibes could be solved pretty well by filling the rubber part of the CB with something like permatex ultra black... or any other hard silicone to stiffen up the rubber, as that is where the take off vibes come from.

 

nd4spdbh, what you said is absolutely correct. When I installed both spacers the drive shaft was practically straight. I thought for sure that would be it. It makes sense what you said & that is exactly what happened.

Before settling at 1/2", how much drop did you test it out at? Did you ever do more than 1"?

Interesting theory regarding the CB also.

How much lift do you have? I'm at 4"'s front and back.

I wonder if

Thanks.

 

This.
And don't dismiss that your takeoff vibe could also be slight axle wrap.
I am also a proud owner of the same shudder.

 

I found this video quite helpful

http://youtu.be/f1m-Fh5kiRU

 

Good video. Although I feel like there are a few guys in the shop waiting for their phones back so they can go home.

 

I was thinking the same kinda thing when I watched it the first time , lol

 

yes while in a perfect world that would be ideal. to make the trans output as close to zero as possible and have equal and opposing angles at the center / rear joint.

PROBLEM is, then you now have a larger angle at the center joint... this by nature of a u joint, creates a side load. this side load turns into an oscillation felt as the take off vibe due to the weak center carrier bearing rubber.

I actually got driveline angles almost near perfect. I had .6* at the first u joint, 6.2* downward angle at the center, and 6.3* upward at the rear pinion. Perfect on paper and perfectly smooth at crusing speeds. (by turning the CB upside down i was able to move the cb position up as high as possible)

But due to the now rather large angle at the center carrier... the oscillation due to the weak rubber at the center carrier got so bad on take off, that the drive shaft moved more then the 3/4 of an inch of clearance it had between it and the cross member and actually knocked the cross member!


I have been toying with the idea of 1. filling the rubber of the CB to stiffen it up to reduce deflection of the CB and thus driveline vibe on take off. and 2. setting the center joint close to zero, getting the front and rear joints at opposing equal angles then Rephasing the driveshaft by spinning the slip joint (4x4 rear drive shaft has one), or the center yoke on the splined part of the driveshaft. Problem is i think both of those spots are indexed and can only be put on one way.

Believe me i have put ALOT of time into trying to eliminate all vibes, and out side of rephasing the drive shaft, stiffer CB, or a one piece, theres just no way you can get rid of ALL vibes.

 

4 runner single piece eh? Did you have to modify that or is it bolt right up (assuming off the 4x4 4 runner as you would need a slip joint)

 

Been going down the same tooth-rattling road. I started with an OME CB drop, then added washers until I ran out of bolt length. I realized I was at 1.25" and was getting close. I ordered the Streetaco 1.5" CB drop but it hasn't come yet.

I did manage to eliminate the take off vibe, but have a vibe at 17-20 mph and a 4 second oscillation at 40 mph. Each washer I added reduced both of these, so I'm hoping the 1.5" drop does it.

 

So grom factory that's how it sits? I've had it lifted so long I forgot how it looks without the CB drop.

HHMMMM. Need to look into that.

So did I. Thanks.

HAHAHA!

Yikes! I thiught about foipping the carrier bearing also but considered the steep angle on the CB and decided not to.

Good idea but I'm 2WD.

Please keep me posted.

Nice work.

 

Was there a specific reason you didn't just pop out the existing u-joint and utilize your Tacoma pinion flange with the new 4runner shaft? Curious if the u-joints are different sizes for the Tacoma and 4Runner.

 

interesting. does the 4 runner 4x4 shaft come with the double cardian? my moms 07 2wd 4 runner has a single piece drive shaft but with standard u joints at either end and no slip joint but rather a slip yoke at the transmission.

 

Great info thanks +1.

 

ahhh gotcha. yeah i knew the 3rd gen 4 runners had the double cardian, just like the 1st gen tacomas. I though at first you were talking about the 4th gen 4 runners.

Though id be curious to see what a 4th gen 4x4 4 runner had, probably 2 u joints and a slip joint... but if it could be cheaply extended it should bolt right up!

 

Yup, solid shaft is the only 100% cure I've read about. I've been researching this driveline thing for months, if you want to keep stock drive shafts with a lift, you have to keep throwing variables at it, test it, and do it again.

Spend a few hours here reading all the threads on driveline vibrations. Some guys add an OME CB kit and it's done, some need to add a few washers. Some need to add a 2-4 degree rear axle shim. Some need a 1.5" CB drop kit from Streetacos. Most need some random combination of all.

And in the end, you might get rid of 90% of the vibrations. My advice to anyone doing a 3" lift on Gen 2- plan on spending potentially another $150 and a few hours of labor to get things right, weeks with delivery time figured in. A lot of trial and error.

 

yup. id even be happy with the 2 piece design and double cardian center joint out of the 1st gen.