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Sun Dec 14, 2008 11:23 am

OK
I'm working on building a drag bug but it has IRS, I seem to recall that some one said that IRS does not stand up well to drag racing. What is the weak link, is it the CV's themselves? I seem to recall that offroad guys used to run Z-car halfshafts years ago, I have a set of spare 510 halfshaft floating around and making adapter to mount then should not be a problem. I know a couple of guys running Z-cars with SBChevys in then that make over 400 HP and they dont have any problems with the halfshafts. Now I know some of you guys are going to tell me to convert to swing axle but I dont have one and am trying to do this on a budget.
Thanks for any help.

Earthquake

Sun Dec 14, 2008 12:31 pm

I've spun an output shaft off the side gear, and grenaded a cv joint. I've now upgraded to type 2 cvs and had no issues since. Depends on the HP your running and how much you abuse the car.

Sun Dec 14, 2008 2:53 pm

The weak link in the driveline is the CV's, and the diff outdrives. Like gonebuggy mentioned, you could upgrade to the type 2 CV's, or better yet the type 181 Thing joint's. Thing joints hold up to quite a bit of abuse when the axle deflection is held at a minimum as it would be in a street/drag car. The off-road guys use the bigger Porsche joints because they need the extra stength to compensate for extreme axle angles, which is usually the cause of failed CV's on a buggy. A stock 15 tooth IRS diff side gear also will hold up to quite a bit of abuse, and you can get a Thing CV cup or an aftermarket cup for the bigger joints for the Beetle tranny. If you have trouble breaking them, there are side gears for a Beetle IRS diff that are custom made that have the bigger Bus splines for the CV cups. A stock Thing half-shaft axle is quite stong as well, but you can upgrade to an aftermarket axle like from Sway-A-Way. So, an inexpensive strong combo would be Thing stub axles, Thing CV's, Thing half-shaft axles, Thing drivecups, and a 15/10 tooth superdiff. A more expensive slightly stronger combo would be Chromoly stubs for Thing CV's, Thing CV's with Chromoly cages, Sway-A-Way halfshaft axles, Chromoly Bus splined Thing CV cups, and 15/10 tooth super diff with the aftermarket side gears with the Bus splines. You could also upgrade to the 930 Porsche CV's, but many feel it is unnecessary. That will take care of the driveline/axle portion, but if you are breaking the gears within the superdiff, you will need to upgrade to a spool, or use a Bus trans with the bigger gears/diff.

Sun Dec 14, 2008 3:06 pm

Just go swingaxle if you're on a budget. With all the IRS stuff you're going to break, your money will be better spent on swing stuff with less failures.

Sun Dec 14, 2008 3:52 pm

jbbugs wrote: Just go swingaxle if you're on a budget. With all the IRS stuff you're going to break, your money will be better spent on swing stuff with less failures.

I've gotten multiple sets of good used Thing drivelines, including stubs/halfshafts/CV cups from $150 to $250. This will be stonger than a stock Swing Axle. If you need the HD S/A's, you probably end up spending more on just the axles than the used Thing IRS stuff, then you'll still need the tubes/springplates. Yes, the more expensive IRS setup would be more than the more expensive S/A setup. If you allready have an IRS suspension/trans, then you'll end up spending more for the budget setup if you need all the S/A parts/trans to convert.

Sun Dec 14, 2008 4:29 pm

A swing axle is stronger having less parts and is lighter also, the IRS controll arms are heavy. I changed my old car from IRS to swingaxle and it was a lot more stable at high speed even thou the controll arm bushings were urethane.

Sun Dec 14, 2008 6:29 pm

an irs car is way more stable because of the full tire contact at all times. and sure some irs set ups are heaver so that means you need to step up in the HP/TQ department and over come the extra pounds, not a problem. if you were to have the option to build both and you went to swing and you had a insudent on the top end were it got loose and possibly crashed, it could have possibly been prevented if you would have ran IRS becaes the tires wouldent have tucked like the old swing. many and i will say many old race cars would have been hear today if they would have ran the irs system. just my two bits . JD.

Sun Dec 14, 2008 6:32 pm

I'm running a ZF LSD, 944 stub axles, Type 2 CVs and Type 181 flanges and so far so good. But my car is not a dedicated track car.

And if you have the budget, the Folts setup is the ticket.

Sun Dec 14, 2008 6:57 pm

930 cv's chromoly sway away axles things stub axles, been runnin full drag like this for 3 years, haven't snapped axles, or cv's since.

Sun Dec 14, 2008 7:03 pm

I thought I would post a pic of the Datsun axles, I don't think it would be to hard to make a flange that welds to the stock CV flanges.

https://www.thesamba.com/vw/gallery/pix/505534.jpg

Earthquake

Sun Dec 14, 2008 7:28 pm

rgdedge wrote: A swing axle is stronger .....
This is false. IRS can be made to never break.
Besides, this topic isn't an argument between swing and IRS, the guy wants to know how to make IRS reliable at the track.

I know a guy who's running deep in the 9s with stock Bus CV joints. 930 CVs are not required, and not desired due to their extra weight. You don't need to convert to Datsun U-joints, Bus CVs are much easier, cheaper, and are bulletproof. Many years ago I worked with a Datsun guy, and he told me the hot ticket for them was to convert to Beetle CV joints. The grass isn't always greener.
If you convert to Datsun U-joints, you must fab up some kind of axle retainment device around each axle, accoding to NHRA rules. That's because when you break a U-joint, the axle starts flopping around. Break a CV, it is contained.

Sun Dec 14, 2008 7:42 pm

Bruce
The reason they used CV's on Datsuns because the stock axles would over-heat on long road races and melt, and then they would usually only put one on the inside joint, at least that what they did on the BRE 510 they even went so far as to mount a fan on the axle to move air over the inner joint. The only reason I thought about using them is be cause I have them on-hand. Thanks for all the imput though.

Earthquake

Sun Dec 14, 2008 10:28 pm

When i had my trans converted from a swing to an IRS (dunebuggy trans)I went with the 091 outputs from the superdiff main advantage is strength vs a type1 style.I can use actual type 2 flanges the shaft is bigger all the way out.They werent cheap i paid about 225 for them.I have a rancho pro comp trans and they knew it was for off road and a mid travel they said the stock shafts can twist with hard off road use

too bad my gears arent for drag racing or it might work out for you i have it for sale right now its a 4.37 r&p,stock 1-2 1.71 3rd,and 1.43 4th

Mon Dec 15, 2008 1:14 am

stick with irs, in the end it is a much better setup.

too many people do whats cheap rather than what works better or is safer

Mon Dec 15, 2008 8:11 am

I've been running an IRS drag car for over 30 years. the side gears in the diff was where I first had trouble. I since switched to a spool and no more issue I've switched to t-2 cv joints with chrome moly cages and I run saw axles. how ever I'm having to upgrade to saw 300 m axles do to the std saw axle are not holding up any more

Mon Dec 15, 2008 10:42 am

Is it the shock load of launching/slicks that kills CV's or just high torque/horsepower in general?

Mon Dec 15, 2008 11:31 am

mynameistory wrote: Is it the shock load of launching/slicks that kills CV's or just high torque/horsepower in general?

In the instance of a Beetle CV, both. If you upgrade to a Bus/Thing CV, they will take care of almost all failures.

Mon Dec 15, 2008 5:07 pm

do you need to change the flanges on the thing Cv,s for type 1 set up

Mon Dec 15, 2008 5:28 pm

Thing and Bus CV's are 100mm in diameter. Bug CV's are 90mm.
If using Thing parts on a Bug, you need the stub axles, axles, CV's, and flanges to complete the conversion. Some years of Porsche 924 & 944 used the same stub axles as the Thing.

Thing CV's and Bus CV's have different sized balls inside, but are the same on the outside and either will work.

Search in the Off-Road forums for more info on this conversion. Those guys do it all the time.

Mon Dec 15, 2008 9:36 pm

Will type 2 CV's fit on type 1 axles (are the splines the same)?