Does driveshaft angle matter?

[FireDancer]

It's been a long time since I've posted here, but I've done a load of searching and reading and I can't find an answer to this question. If I've missed it, please point me in the right direction.

I converted my Baja to IRS about 20 years ago, and for most of the time have run stock boxed arms, 944 CVs and stub axles, and Thing/Trekker driveshafts. I've never had issues with noisy CVs.

I've made myself some 3x2 arms (3" longer and 2" wider), which I'm running with VW bus axles, 944 CVs and stub axles. The CVs are a fresh set that I've polished and clocked, and they have brand new high angle boots.

The travel is limited so that the CVs are happy at full droop, and there is plenty of plunge available at all points of the suspension travel.

My issue is that the CVs are noisy under acceleration, and I'm concerned that I'm damaging them. I've tried my original CVs and the newly polished ones, same deal.

So my question is, does the angle of the driveshafts from above matter? My understanding was that with 3x2 arms you don't need to move the gearbox, and in all my static testing the CVs were happy with this setup. On a stock setup the hub sits forward of the gearbox output flange, but with my new arms the hub sits aft of the gearbox output flange. Under acceleration is the driveshaft being pulled into the gearbox by the torque?

So on your 3x2 or 3x3 setups have you moved the gearbox back? If you've moved it did you go with the full 3", or is there a magic middle point?

Or is is something else I've missed? You guys have lot more experience with longer IRS arms than me so your advice would be appreciated.

[Vanapplebomb]

You don’t need to move the gearbox for longer arms. The CV joints don’t care what direction the axle moves. Backwards, forwards, up, down… makes no difference so long as you don’t exceed the articulation and plunge of the joint… figure 25* is about the max for T4 cv joints, which is what non-turbo 944s used.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[jsturtlebuggy]

It is not only the movement of up and down angle of degrees you also have to account for angle of degrees the offset between CV flanges too.
You have to add to the total.
Meaning you can get more up and down angle of degrees if CV flanges are straight across from each other.

Also do your replacement CV joints have the same size balls as your old ones?
If CV balls are larger you won’t get as much angle out of them.
Type 4, 924 CV balls are 17.5mm verses a type 2 that are 20mm
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Joseph
Fair Oaks/Orangevale, CA
Elrod Motorsports
Motion Tire Motorsports
Having fun with Dune Buggies since 1970
Into Volkswagens since 1960

[FireDancer]

[FireDancer]

[Vanapplebomb]

[sailtexas186548]

I had a CV (new) that for some reason did not let the axle plunge smoothly, and was causing the CVs to make all kinds of noise when it hung up.

I replaced the center star, greased the splines on the new one real well, and the problem was solved.
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it's more fun loud and dirty

[jsturtlebuggy]

You saying you polished the new CVs, are they moving freely? You want the CVs to be very loose. To almost like they are worn out. Making the openings in the CV ball cages so balls move freely.
On my own buggies I have stepped up to 930 CVs (one buggy is still type 4 CVs). I am using the Empi 930 race CVs, They are very loose fitting new. To the point if your not holding right the balls fall out.

Also if you are using a Bus transaxle, it being a hypoid design the mainshaft is not in the center like a Bug transaxle. It offset approximately 1/4in. Depending on how trans ais mounted you may come up with two different measurement between CV flanges.

Axle length does matter.
To find correct axle you need is to measure from center of each CV (the cup part) flange when they are parallel in height.
With this measurement subtract a 1/4 to 1/2in for correct axle length.
If you are using stock length axles the may not be long enough.


I am using the Empi chromoly axles on my buggies. Have had great luck with many years running them. They have long splines and no inner stop on them. Now I have had to shorten some of them to get correct length for different applications because unlike SwayAway they don’t make custom lengths only standard different lengths.
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Joseph
Fair Oaks/Orangevale, CA
Elrod Motorsports
Motion Tire Motorsports
Having fun with Dune Buggies since 1970
Into Volkswagens since 1960

[FireDancer]

[FireDancer]

[FireDancer]

[FireDancer]

Can I get some expert eyes (and ears) on my videos?

Here is the plunge on the CVs at ride height, both sides and from a couple of angles:

Link


RHS in motion from behind:

Link

And from above:

Link


LHS in motion from behind:

Link

And from above:

Link


I'm not running crazy angles, but they're not as smooth as I'd expect from freshly poshed CVs when they're put under power.

[rayjay]

Maybe it's an optical illusion but it looks like the outers have more of an angle than the inners. Seems impossible !! Also, It looks like the outers are at a too severe angle. Visualizing what I am seeing it seems like the inner race and balls would be very near or beyond the edge of the outer race.

[FireDancer]

[rayjay]

You are going to have to take the boot off, reassemble and then be able to look at the innards of the joint while you spin the tire.

[tripicana]

What about clocking the inner and outer cv to each other?
There used to be a tech page from outbacksubaru but can’t find it.
Basically you want the bolt hole on the outer cv with a big gap to line up with a bolt hole on the inner cv with a small gap.
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foam cowboy hats aren't good helmets.

[FireDancer]

[FireDancer]

[jsturtlebuggy]

Have you measure how many degrees the axles are from being center flange to flange?
Pictures show that it looks like it may be there is a lot of off set between flanges and the rib part of boots are touching.
_________________
Joseph
Fair Oaks/Orangevale, CA
Elrod Motorsports
Motion Tire Motorsports
Having fun with Dune Buggies since 1970
Into Volkswagens since 1960

[FireDancer]