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Broken IRS end gears.
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vwracerdave
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PostPosted: Mon Apr 12, 2021 11:01 am    Post subject: Broken IRS end gears. Reply with quote

1900 Lb. Ghia with 160 HP 2165cc and slicks..

Last year I had an IRS transaxle built with a Super Diff. I made 13 passes and broke the splines off the long end gear launching at the line. I simply took it apart and replaced it with another used end gear and thrust washer. It broke again after 8 passes, same exact thing broke the splines off the end that the CV flange goes on. I have over 150 passes on this Ghia with a bigger 170 HP 2276cc and never broke the end gear.

Is there any shimming or end play measurements that I missed? Is this a common weak link that breaks and is simply not strong enough for drag racing? Could this be from a Super Diff that was not machined correctly?

Many years ago I got a transaxle with "super splines" and it only lasted 9 passes before the welded splice broke. I was told they are NLA and replaced it with a stock type I end gears and it's still working today. I'm aware of the Folks diff with 091 end gears but that's a $1200 upgrade and I'm running a SSC case.
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PostPosted: Mon Apr 12, 2021 11:31 am    Post subject: Re: Broken IRS end gears. Reply with quote

Add H.P seem to work for the 2276 Laughing ,,Or
Quit launching so hard and add a Turbo ,,, same E.T's Laughing Laughing Laughing
sounds like the super diff housing is 'off' ?
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Ohio Tom
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PostPosted: Mon Apr 12, 2021 12:55 pm    Post subject: Re: Broken IRS end gears. Reply with quote

OK, there is a big difference in strenth between the 11/17 tooth spider/side gear, compared to the later model 10/15 tooth spider/gear diffs.

The 10/15tooth setup has better "lead out" on the splines that help prevent breakage.

HOwever, even with the 10/15tooth upgrade, it will be the weakest link you have.

The permanent fix is:

(NLA) super splines. They used 15tooth side gears with 091 output splines. NO longer available as far as I know.

091 diff. Weddle makes a Type 1 diff that accepts 091 spiders and gears. This is the best of the best for open (affordable) diffs.

Peloquin. Money is no object. I would say they are un-breakable, but a member here broke one...
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PostPosted: Mon Apr 12, 2021 2:20 pm    Post subject: Re: Broken IRS end gears. Reply with quote

Ohio Tom wrote:
OK, there is a big difference in strenth between the 11/17 tooth spider/side gear, compared to the later model 10/15 tooth spider/gear diffs.

The 10/15tooth setup has better "lead out" on the splines that help prevent breakage.

HOwever, even with the 10/15tooth upgrade, it will be the weakest link you have.

The permanent fix is:

(NLA) super splines. They used 15tooth side gears with 091 output splines. NO longer available as far as I know.

091 diff. Weddle makes a Type 1 diff that accepts 091 spiders and gears. This is the best of the best for open (affordable) diffs.

Peloquin. Money is no object. I would say they are un-breakable, but a member here broke one...


Tom covered it anymore for an IRS if you have passed the threshold of the standard Type 1 splined outdrive.

I would think that the trans builder would have used the 15 tooth outdrives in both, but it’s something to check.

You must have got a bum Superspline outdrive. I’ve known more than a few to put 300+hp through them without issues. I had amultiple ads looking for Super Splines for 5 years before Dave/Eric’s 091 internal existed only to find two pair, so they are definitely non-existent.

I know of one builder that has bored the carrier bearing race location larger on a single side cover case to install the 091 internal diff, but most that deep are using the dsc Rhino case. 091 outdives/spiders are pretty hefty, and with their popularity presently, I can see there being components available for a while. For a street/track car that doesn’t need any type of tbd/lsd, this is the way to go imo.

The Peloquine/Quaife diffs with the 091 outdrives can be installed into ssc cases. I would think they should last hundreds of passes in something less than 2000lbs./200hp. I’m contimplating a Peloquin diff in a ssc case for the next build on the Superbeetle.

Here’s a pic of a 17 tooth outdrive compared to a 15 tooth one. The 17 tooth has an undercut where the splines end that breaks, where as the 15 tooth has the splines simply cut onto a continuous diameter section.

Image may have been reduced in size. Click image to view fullscreen.
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vwracerdave
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PostPosted: Mon Apr 12, 2021 3:02 pm    Post subject: Re: Broken IRS end gears. Reply with quote

I do have the 10/15 spiders & gears.

Weddle list the Peloquine as 'out of stock'.

Is there any possibility the R&P gear depth and backlash were not set up correctly causing the extra stress on the end gear gear splines?
gkeeton, you said in your book about using 2 thrust washers on the short side end gear. I broke the long side as that is the torque side.

It was a lot simpler to repair when I was breaking type I CV joints. Now that I've upgraded to Bus/Thing CV's and axles I guess the side gears are the next weak link.
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PostPosted: Mon Apr 12, 2021 3:19 pm    Post subject: Re: Broken IRS end gears. Reply with quote

vwracerdave wrote:
I do have the 10/15 spiders & gears.

Weddle list the Peloquine as 'out of stock'.

Is there any possibility the R&P gear depth and backlash were not set up correctly causing the extra stress on the end gear gear splines?
gkeeton, you said in your book about using 2 thrust washers on the short side end gear. I broke the long side as that is the torque side.

It was a lot simpler to repair when I was breaking type I CV joints. Now that I've upgraded to Bus/Thing CV's and axles I guess the side gears are the next weak link.


The bigger CV’s is what’s creating the added stress, and showing the next weak link. I’ve mentioned about multiple thrust washers here, but maybe you are thinking of Casting Timmy in the way of a book/manual. Endplay of the outdrives imo plays more into the life of the gear teeth, but having the shafts pop in/out with excessive endplay could contribute. I’ve seen diffs that were on the loose side with one thrust washer, but too tight with two where the housing/side cover needed turned down for extra clearance. I wouldn’t go any tighter than .005 endplay so that the diff gears still have room for oil in between them.

Maybe place a wanted ad here, on some of the FB groups, and even contact Peloquin for a diff if you’re thinking of going that route. You’ve got me now thinking about finding one. The 113 pinion bearings were nla for over a year before they finally started back up production.
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PostPosted: Mon Apr 12, 2021 4:20 pm    Post subject: Re: Broken IRS end gears. Reply with quote

Are you running your slicks really soft?
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PostPosted: Mon Apr 12, 2021 4:25 pm    Post subject: Re: Broken IRS end gears. Reply with quote

You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.
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PostPosted: Mon Apr 12, 2021 4:38 pm    Post subject: Re: Broken IRS end gears. Reply with quote

you sure the cv is assembled correctly.....it can be assembled correctly and swivel and incorectly and not swivel...Im sure you have checked thel real well but it may be worth taking that side totaly appart..if you dodnt asemble them it may have a wonkey ball or somethen. if all else fails...soften up the lunch. and be sure all mounts are good as well as frame hornes and that nothing is twisting at launch.as well as the dog leg& bushings.
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PostPosted: Mon Apr 12, 2021 4:41 pm    Post subject: Re: Broken IRS end gears. Reply with quote

I run 20 PSI in the 26X6 slicks.

mcmscott wrote:
You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.


I broke the end gear on the launch as the clutch was released. Car didn't move 2-3 feet. Ghia will normally wheelie with the front wheels barley 2"-3" off the ground.

I never thought to consider that. A few years ago I did replace the spring plate urathane grommets and trailing arm bushings.. Trans has solid mounts and I'm also running a Berg traction bar. I guess I'll have to check out the shocks. Thanks.



I've put maybe 300 street miles on this trans and have had no problems driving.
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PostPosted: Mon Apr 12, 2021 5:47 pm    Post subject: Re: Broken IRS end gears. Reply with quote

mcmscott wrote:
You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.


What would be a good way to confirm it, then confirm you got rid of it? Gopro on the starting line?
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PostPosted: Mon Apr 12, 2021 5:51 pm    Post subject: Re: Broken IRS end gears. Reply with quote

[email protected] wrote:
mcmscott wrote:
You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.


What would be a good way to confirm it, then confirm you got rid of it? Gopro on the starting line?


That would make the most sense. Watch the vid after the run and confirm if there is wheel hop.
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PostPosted: Mon Apr 12, 2021 5:52 pm    Post subject: Re: Broken IRS end gears. Reply with quote

[email protected] wrote:
mcmscott wrote:
You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.


What would be a good way to confirm it, then confirm you got rid of it? Gopro on the starting line?


I was thinking the same thing. Check everything for worn bushings/tightness. Add some air, and video the launch in slo-mo. See if you can figure out if you're hopping and shock loading.

Breaking shit sucks. Hope you can figure out what's going on.
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PostPosted: Mon Apr 12, 2021 6:23 pm    Post subject: Re: Broken IRS end gears. Reply with quote

[email protected] wrote:
mcmscott wrote:
You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.


What would be a good way to confirm it, then confirm you got rid of it? Gopro on the starting line?

There are all sorts of systems to record suspension data (travel, velocity, cycles, etc). I helped a buddy set up the system on his motocross bike, and then he used the info to help fine tune the rates and valving. Super cool system, it linked via bluetooth to his iPad and gave you plenty of ways to look at the data. No doubt pricey but it would show you exactly whats happening.
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PostPosted: Mon Apr 12, 2021 6:27 pm    Post subject: Re: Broken IRS end gears. Reply with quote

esde wrote:
[email protected] wrote:
mcmscott wrote:
You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.


What would be a good way to confirm it, then confirm you got rid of it? Gopro on the starting line?

There are all sorts of systems to record suspension data (travel, velocity, cycles, etc). I helped a buddy set up the system on his motocross bike, and then he used the info to help fine tune the rates and valving. Super cool system, it linked via bluetooth to his iPad and gave you plenty of ways to look at the data. No doubt pricey but it would show you exactly whats happening.


Do you have any brand names, or links?
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esde
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PostPosted: Mon Apr 12, 2021 6:30 pm    Post subject: Re: Broken IRS end gears. Reply with quote

This might be the one we installed
https://motioninstruments.com/products/moto-kit
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PostPosted: Tue Apr 13, 2021 6:13 am    Post subject: Re: Broken IRS end gears. Reply with quote

mcmscott wrote:
You have wheel hop, you may not feel it but you have it. Stock irs end gears will sustain 11.60's in a full weight sedan if set up up correct.


NOt really a fair statement.

It's about 60' times. Not 1/4mi ET's.

I was breaking Stock IRS splines at 13.50's running 1.7sec 60' times. (yes, proper setup and no wheelhop).

Now if you got the power to run 10.90's and back down on the launch to a 2.0sec 60', then yes, you can run 11.60's with stock stuff.


However, that's not normal drag racing.

There is no question that at 160hp, the weak link is the output splines.

I have seen more broken ones than I care to. I bet you have too......

Scott, I'm really surprised that you don't have more to share here.
I know that you do this stuff way more than I do and have lots more insight.
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PostPosted: Tue Apr 13, 2021 8:18 am    Post subject: Re: Broken IRS end gears. Reply with quote

My buddie was running 11.60s in a full weight 69 sedan, mid 1.60s 60 ft time.
I was racing the march meets in my 67, very braced car, solid mounted, solid mid mount, braced truss, brace from horns to the body and a couple other things. That car shot out of the hole without a shudder. Came back to the pits and a buddie says "you got some serious wheel hop" I tell him no way possible, he had a camera on a tripod behind all us racing. He showed me the vid in slow motion and you could see the stinger coming away from the body and returning about 3 in! You could also see the tires wrinkle, unload and move foward and back at the same rythem as the engine was moving. All this without feeling not even a shudder, trust me, you have wheel hop. Yes I have seen more broken trans parts than most anyone on this site.
I've slowed down trying to answer questions I know as facts due to all the people here that obviously know way more than myself about transaxles and would rather try to tell me I'm wrong.
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PostPosted: Tue Apr 13, 2021 8:34 am    Post subject: Re: Broken IRS end gears. Reply with quote

Hey, thanks for sharing..

I got you to come out of your shell... LOL..
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PostPosted: Tue Apr 13, 2021 8:35 am    Post subject: Re: Broken IRS end gears. Reply with quote

I ran 12.20's with thing/bus CV's and never broke a side gear..

but I also ran 7" slicks @ 14psi...

try dropping the tire pressure
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