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Front axle angle - what did you do? (4.5" lift)

1K views 5 replies 3 participants last post by  Racemau5 
#1 ·
I've been searching and searching but have not found a good answer (conflicting information all over). I have lifted my CJ7 4.5" and currently the front drivetrain geometry looks like this:



I have added 2.5* shims to lower the pinion after the lift was mounted (to get better castor angle).

The driveshaft lenght is 34". With the current geometry the difference between the two operating angles is 8*.
This gives a joint life of around 35% compared to 0*.

Now, what should I do? Some say to just install a normal drive shaft (non-cv) as driveshaft vibrations is not a concern with the relative low rpm's the front shaft will see in 4x4 (this is of course very different for the rear driveshaft).

So my questions is: What did you do? - And how did it work out for you?

Thanks
 
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#2 ·
I don't know if I am answering my own questions. But it seems that 2.5* shims gives me AROUND 2.4/2.5* as the pinion as well and it lowers the driveshaft angle around 1*. If I shim the front axle a total of 5* it would give me axle operating angle of 10.2* and TC operating angle of 15.8*. A total of 5.6* between the two which is considered more acceptable for vibrations. However, the expected lifetime for the joints will still suffer significantly. (20-40% of normal expected lifetime which is 3000hours. In my case they would last 500-600 hours which is more than I will drive in 4x4 the next 10 years). Remember I am only talking about the front driveshaft.
 
#3 ·
in general no matter the year jeep. front is a compromise of caster angle and drive shaft angle. Leaning to drive shaft angle to keep it happy. Much of this depends on type of drive shaft and what speeds vibration in DS happen. in the end speed limit of the drive shaft. The only REAL solution if none of the above works for the speed intended is re-clocking the Cs on the axle housing to have the correct caster and needed pinion angles for the type of driveshaft used.

True in a no load front drive shaft a double cardan/Cv 3 joint type DS wont need to have the pinion parallel to the DS. BUT there is a speed limit to this if the front DS is spinning. once you past that limit even in a NO load vibs start. these can wear out parts and even lead to catastrophic failure.

When people say Cv type the wording can be confusing to type of DS we talking about.

So here is examples of: Cv/3 joints


 
#4 ·
Hi 222Doc

Thanks for your answer. I am not sure I am any wiser though. I have locking hubs on my front axle, so during normal (high-speed) road conditions the front driveshaft will not spin.

My questions is really, can I successfully run a conventional 2 joint driveshaft where one operating angle is 8.8* and the other is 16.8*?
 
#5 ·
Those angles are pretty steep for such a long driveshaft and only 4.5" of lift. I've never measured my front u-joint angles, but with my spring over, my rear u-joints were around 15* or 16* IIRC. And that's with a T18/D20 and a very low pinion 9" rear. Is your front tcase output angled UP like in the drawing? Is your D300 clocked flat?
 
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