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Volkswagen Trailing Arms

Lengthened Trailing Arms

These are used to increase the tire track (width) and move the tires back for more clearance as well as increased suspension travel, which is desirable for absorbing the shock of landings after jumps and allow for greater articulation over uneven terrain - such as when driving over rocks.

6x6 Trailing Arms

This can get pricey and will often necessitate longer axle rods, upgraded CV joints and sometimes an upgrade to a bus transaxle to handle the stresses you plan on subjecting your driveling to.

Arm Sizing

Lengthened arms are generally described by the amount they are widened and lengthened.  A 4x6 lengthened arm is 4 inches wider and 5 inches longer than stock.

Notching Spring Plates

This is a common practice to gain just a little bit more lift and downward travel.  It is only recommended that you notch your stock spring plates a maximum of 0.24 inches.  Notching them more than this will stress your CV joints and cause undesirable camber, even in an IRS VW.

CV Joint

The CV joints allow you to run your axles at various angles and allows the axles to piston in and out.  Without them, the axles would not be able to articulate and you would be able to run a drive suspension.  If you increase your suspension travel, you will need to account for driveling angles and consider which CV you would like to use.

Type 4 CVs joints include - Porsche 924,944 and VW-181 Thing and they all share the same flanges and stub axle.  This stub will fit into the stock Type 1 trailing arm bearing carrier to allow you to run both Type 2 and Type 4 CVs.

Type 2 CV joints can be used in a Type 1 if you use Type 181 (Thing) flanges and stub axles.

If you would like to use 930/935 Porsche Turbo CV joints and axles, it will cost you.  Besides the spendy CV joints X 4, and axles, you will need specially fabricated axle shafts and stub axles.

Ref:

CV joint 101

High Angle Drive Axles

These use high angle U-joints and can get pretty spending.  There is concern that they don't give like regular axles and will destroy a VW transmission.

Ref:

Highangledriveline

never seen these before, are they better that cv's?

Axles

According to Blind Chicken and others:

Size	Axle Length	Transmission	From
Stock	15.625"	Converted to IRS
Stock	16.25"	Stock IRS
Stock	18.75"	Bus, 5.75" Rear Section
2x3	18.75"		early IRS bus
3" longer	17.25"	Bus
3x3	19.25"	Bus Trans, Stock Rear
4x5	20.5"		Vanagon automatic transmission left side axles
5x5	21.5"		Vanagon five speed axles - most common
6x6	22.5"		Vanagon automatic transmission right side - rarer

Here is a listing of Sway-Away Axles used in VW applications for planning purposes.

Sway-Away VW  33 Tooth Axles, 2 3/8" Long Spline, Type I, II, III

Sway-Away VW/Porsche 356 Swing Axle Applications

Sway-Away Porsche 930 28 Tooth Axles, 3" Long Spline

Sway-Away Porsche 930 28 Tooth, 3" Long Spline, Racing Axles

Description	Length	Part #	MSRP
Racing Applications	16 9/16"	32416	$525.00
Racing Applications (5-16 cars)	16 3/4"	32416-7	$525.00
Bus Trans, 3" Longer By 3" Wider Arms, Stock Rear	19 1/4"	32419	$525.00
Racing Applications	20 1/4"	32420	$525.00
Racing Applications	21 3/8"	32421	$575.00
Racing Applications	22"	32422	$575.00
Racing Applications	23"	32423	$575.00
Racing Applications	24"	32424	$605.00
Racing Applications	25"	32425	$605.00
Racing Applications	26"	32426	$605.00
Racing Applications	27"	32427	$605.00
Racing Applications	28"	32428	$605.00
Racing Applications	29"	32429	$605.00
Racing Applications	29 1/2"	32429.5	$605.00
Special Order 28 Spline Axle Set, Racing	Any	32400	$750.00
Cut Fee for Pair of Axles, Racing Applications		32401	$155.00
930  C.V. Porsche Axle Set with Bubble, 28 Tooth	Any	32402	$770.00
Spiroloc Circlips For Porsche 930 Axles, Each		2411	$1.40

Finding Axle Shaft Angles

The easiest way to do this is with protractor on level ground and a little guesstemating.  But if it is raining out or if you don't have a protractor, then you can give a shot at computing it.  The geometry on the rear end of the VW is a little more complicated than one may first consider.  The axles don't just move straight up and down when you hit bumps or tweak your torsion bars.  The rear suspension in part moves in an arc around the center of the torsion bar.  On IRS models, it moves in less noticeable arc that changes the camber for the rear wheels and causes the axle shafts to piston in and out of the CV joints.  And on swing axles, the axle housings force the spring plates to twist as the axle pivots more so on the transmission.

Longer and wider trailing arms my decrease some of the arcing effects of the suspension as it articulates, but can also add other problems - like down right improper alignment, binding, etc.  Note that the following calculators simply calculate 2 point and 3 point vectors and may not reflect exact changes on your VW after you install your fancy lengthened trailing arms.

Two Dimensional Angle Calculator:

Three Dimensional Angle Calculator:

More on the math:

1. The two vectors are represented by:

   f  =  (1, 0, 0)^T

   g  =  (x, y, z)^T

    

2. The lengths are:

   | f |²  =  (1, 0, 0)^T · (1, 0, 0)^T =  1 + 0 + 0  =  1

   | g |²  =  (x, y, z)^T · (x, y, z)^T  =  x² + y² + z²

    

3. The normalized vectors are:

   f_u  =   (1, 0, 0)^T / √ 1

   g_u  =   (x, y, z)^T / √ x² + y² + z²

    

4. The dot product is:

   f_u · g_u  =   (1, 0, 0)^T · (x, y, z)^T / (√ 1 √ x² + y² + z²)

     =   (x + 0 + 0)/(√ x² + y² + z²) = x / r

    

5. The angle is:

   cos θ =  x / r

   θ =  arc cos (x / r)

The final angle calculation seems to make sense as you are comparing the horizontal distance to the new hypotenuse, which should give you the new angle of your axles if it is dropped down y inches or CMs and back z inches or CMs.  But, it's been a long time since I had to do this in school.  If this math is incorrect, then the calculator above is programmed incorrectly.  Please let me know if you think this is the case, especially if you have a solution.

Aftermarket and Other Stuff

Ref:

Beanie Boy 3X3 Suspension Kit

Eagle Performance

Apple Tree Auto

Moreparts second page

Pacific Customs

Chircoe

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