Heavy duty IRS CV joints & axle options for drag & street

[Lo Cash John]

Hi all. I need some advice for my turbo bug and a future transmission build.

My bug is a '73 standard with full interior, -3" narrowed beam and stock IRS rear that's been lowered 1 outter spline. My current motor build (almost done) is an 1835 (my throw 94's in it before to long) with T3 turbo and 40mm Weber sidedraft carb. It's got really good heads and very ported and modified end castings fed by a 1-3/4" T pipe. Sitting in the garage I also have a 2387 with CB Street Eliminator heads, a BIG T3 and a bunch of EFI stuff that may go in next year.

This is mainly a street toy for weekends and nice weather and occasional trips to the local track. My buddy Lester can handle the trans build I want to do but since we've mainly raced swingaxle cars, IRS axle options are a little foreign to us (well, me actually. Lester's in Guantanamo Bay, Cuba for work this week so I can't call him and talk out ideas). What my trans plans are so far are:

White Rhino case with gussets welded to bottom of diff area
Crown IRS suber diff with Type 2 output shafts
4.12 R&P
Gears will be Lester's call.
Whatever tricks he does inside.


Axles & CV joints are the question. I've been told Type 2 CV's should hold up, even with slicks (not sure about that) and Sway A Way stocks the right axle length. The thing is, I'd like to narrow my rear arms by 1" per side for extra tire room. This means I may not be able to use a production axle. Does this sound right? Any IRS gurus please speak up and share your wisdom.

Thanks!!

[Piledriver]

I have been down this road...

Narrowed arms will only buy you so much... You are usually into the bolts on the springplate.& bump stop hard.
Custom wheels with the proper offset will cost far less than the std/narrow arms, which are a very low demand item.
(aircooled.net once sold them for a reasonable price, but John wanted 2X what a typical set of wide/long CrMo arms cost for his personal set, last ones left)
The fellow that used to make them modified the jig for longer arms, can/will no longer make them.

Unless you narrow the torsion and tub the fender wells/go coil over you aren't going to get much more than an extra inch/side.

There are shorter axles available: also one can narrow the splines area on T4 joints to T1 width to give yourself a bit of space at very little cost.
(works with existing T1 spline axles, ends up at std width, 924/Thing axles can have the splines shortened if used with the modified T4 CVs providing ~1" per axle shorter or thereabouts)

[Bruce2]

I recall talking to Richie Webb in the UK about CV joints. He ran deep into the 9s with Bus CVs. I don't know what he's using today now that he's in the low 8s.

Stock VW Type 3 automatic left axles are 26mm shorter than a Beetle axle.

[Lo Cash John]

I'll narrow the arms myself. That's nothing. Getting axles that are the proper length is the concern.

I know about the Type 3 auto axle trick. I'm just not aware if SAW sales a heavy duty axle that length.

Let me ask this: If I we're to use Type 2 CV joints and stock, unmodified arms, what length axle do I need? Same length as stock bug axles? Does simply swapping from Type 1 to Type 2 CV joints have any effect on axle length.

[Ol'fogasaurus]

Just for giggles, here is some information that may or may not help: http://www.blindchickenracing.com/How_t ... nd_cvs.htm

He who must be ignored.

[Marc]

I'm running Type II CVs on my Bug (stock-width arms, Thing FD flanges/944 stubs) but didn't spring for Thing drive shafts - instead I had the inner races of the CVs ground narrower to allow them to fit on standard Type I shafts. This of course reduces their angularity limit, but it's a street-driven car and all I was interested in was the strength.
More info at the thread linked below:

Regular Bug (or 4-speed III) axles are ~16-5/16" end-to-end, and 28mm from shoulder to end (spline/snapring area).
Thing, and I believe also 924/944, are about 3/16" shorter overall but are 33mm from shoulder to end.
Sway-a-Way says their Bus trans-in-Bug axles are 15-5/8", don't know the spline length but presumably it's at least as long as the Thing.

http://www.shoptalkforums.com/viewtopic.php?t=113520

[Piledriver]

You can also counterbore the inner spline area of the T4 or T2 CV to T1 depth (from the inner end) and put T4 CVs on T1 axles with no reduction in CV max angularity, and w/zero damage to the axle. I have yet to ever see or even hear of the splines stripping...
The length ends up the same.

If you do the same trick on T4 splined axles, you can slide the CV all the way in, groove for a snap ring, and get around 10mm each end.

[Marc]

You can also counterbore the inner spline area of the T4 or T2 CV to T1 depth (from the inner end)...

Yes, that would be another way to skin the cat if you were concerned with the angularity and couldn't come up with the right shafts...my machinist said that it would be more costly (those races are hard, and it's much easier to simply grind the whole thing narrower than to plunge out the center). Even going the cheapskate way it still cost nearly as much as my son paid for legit Thing shafts for his baja.
Another "solution" I've heard of is to cut back the inner shoulders of the Bug shafts to allow the Bus CVs to slide on further - but that sounds very shaky to me, it seems like you'd be introducing a stress riser in a spot that's already a weak point.

[Piledriver]

The 944/things stubs can be had for ~$100, IIRC I paid about that with the trans side drive cups included, and got a deal on clean 944 axles w/CVs and perfect OG boots too. (also marked for rotation inner/outer + side by request, asked pre-pull)

It's the axles that can get expensive.

I did the "plunge cut" with a few cheap grinding stones. Worked fine, just required significant patience.
Run them with lube/coolant and they don't even make much of a mess, and nothing gets hot enough to hurt the heat treat running them at drill press max speed...

Did the axle side mod once on my sons super, worked but I didn't like it, polished up the results as much as possible to remove stress risers.

[Steve Arndt]

Bus into bug 1" shorter SAW axles are an option, then trim and cut new clip grooves to shorten the axles further if needed. For limited travel street use it would work.

[Bruce2]

I know about the Type 3 auto axle trick. I'm just not aware if SAW sales a heavy duty axle that length.

Stock axles don't break. No need for anything HD.

[Henryhoehandle]

Another "solution" I've heard of is to cut back the inner shoulders of the Bug shafts to allow the Bus CVs to slide on further - but that sounds very shaky to me, it seems like you'd be introducing a stress riser in a spot that's already a weak point.

It IS shaky.. we tried that once.. the axles broke.

[Henryhoehandle]

Angle is relative to cv failure, imo. The less the angle, the stronger the cv is.

[Clatter]

Early 944s have what you need - stubs, CVs, and axles.

They are everywhere in the junkyards nowadays.

Even 944 left side automatic axles are getting easy to find...

[Bruce2]

Even 944 left side automatic axles are getting easy to find...

What's unique about that? Shorter?