Why T181 flanges
 

Got a question. Why do we need to put t181 flanges on an irs tranny when going to 944 rear arms? From what I see, the pattern is supposed to be the same as the T1. Is this another instance of overkill for strenght, or is it a dimensional thing?

Hello-

There are two seperate things to think about. First, the trailing arms and the geometry they give. There's no reason in the world this dictates new output shafts... it doesn't matter.

But, the second thing is CV size. All aluminum 944 arms have stub axles with the T2-sized CV, and the arms can't be "swapped" for smaller, T1-sized ones. All steel 944 arms also have stub axles with the T2-sized CV, but they _can_ be swapped for stock T1 stub axles. In either case, most of the time, an upgrade to bigger CVs is desired by the person putting in the trailing arms, so they get the tranny output shafts to match.

Take care,

So does a 181 flange mate up with a t1 or t2 cv. I'm just getting confused when I search the forums.

It matches up with the T2 CV.

Alex

Thanks Alex, it makes sence to me know.

So, are there no bus tranny flanges that would work in a t1 tranny?

No, but 181 flanges WOULD allow you to use bus CV's (big) or 944 CV's (bigger). Most of the racing transaxle shops have their own 181 type "conversion" outputs also but are more $$. You don't "have to" go away from T1 CV's at all unless you intend to abuse them (which I definately intend to do :D ).

A link to some comparisons of the different sizes of the CV's and axles.....
http://www.blindchickenracing.com/Ho...es_and_cvs.htm

i'm using 091 output shafts T2 cv's in my IRS tranny.

That's good news Pete. I had the understanding that the only way to adapt was with 181's.

so how do these different options in the use of CV's and axles translate to the added distance from the trans to the hub? assuming early alloy arms add 1 3/4" per side, where is that distance made up?

john and i are trying to figure out the right combination of parts to use, without overkill and unneeded additional cost but still doing the right thing.

i will have 176HP TIV, T1 RAT trans, IRS, early alloy 944 arms and spring plates. from other posts i have gathered this as one option:

trans > T1 output flange > T1 CV > T1 axle > T2 CV > 944 stub

sorry for so many questions in one post.

Good post zen.
I think we are all struggling with this..... well except for Shad who seems to have it all locked down:cool: !
The set-up you have listed seems straight forward. From what I gather, the axle is where you make up the distance and you may have to buy new ones at a specific length ($200:eek: I think)
I decided that I wanted the extra size of the 944 CV's for my long term HP plans but lots of drag guys still run the T1 CV's up to a certain HP/traction limits, several have posted that smart driving is the key regardless of the size of your "joint":silly: !

>i'm using 091 output shafts T2 cv's in my IRS tranny.<

How? I looked at this option and it seemed impossible as the splines are completely different.

As for the Thing output flanges they are not needed if as Panel said you are not beating the car hard off the line. Heck I think most people doing the CV conversion do not need it!

The reason I am switching to T2 CVs is that I need the greater working angle for the IRS bus suspension conversion. The T1 I think gives 18 degress where the T2 gives 22 or 24 degrees. The 411/412 gives the best but are hard to find. As I understood it the 944 used T2 CVs, but this is not verified.

The later 944s with AL arms used longer axles, find the ones that work or get SAW axles to match your needs. I think mine were 125ish for a pair.

the flanges are 091 to which the T2 cv's bolt to, then the beetle axle to another T2 cv, then to a beetle/T2 stub axle.

the tranny has Super Spline Drives which are thicker much like a T2/181 output shaft. the output side (spline side) mates with the 091 flange.

call kevin at KSR

he biult my trans and could tell you what's going on. i could be confused, getting things mixed up.

pete

good call pete. kevin is building me a trans brace right now. didn't even think to ask him. not sure if he has done any conversions to 944 arms though.

Pete's side gears in his t1 trans have been cut and spliced to 091 splines. I had a pair of these but were spliced to 002 bus splines and ran all t2 cvs then, most better trans people can supply these but I *think* Weddle or Transform is the source. My spliced side gears lasted until the next weak link broke-the spyder gears.

the spider gears in my tranny are 10 tooth. its been a year, but i remember Kevin saying he had to change them to a gear which have less teeth, which is stronger. i believe he also modified my sidecovers too. i think he got the super spline shafts from Weddle.

You have 15 tooth side gears instead of 17 tooth, which takes the 10 tooth spyders instead of the 11s, the strongest VW made. And they were spliced to 091 splines. GOOD parts!

I am in the process of building the rear setup using 86 944t alu. trailing arms. These are the parts I've collected,
1.86 944turbo alu. trailing arms with stub axle
2.86 944turbo complete rear axle with cvs (100mm)
3.181 output flange to mate to the irs transmission.
Are these all the parts I need to put this together? :)

Good info Pete! I have not seen that setup before with those output shafts.

Silver, yes that is all you need to get the drivetrain going.

I hope the 944 turbo axles are longer then the bug ones, otherwise you need T3 bus (vanagon) axles. Those also have 100mm CV joints and have the right length. At least that is my experience...
Cheers,
Walter

i'm still so confused. the T1, T2 and 944 axles all have different lengths. the early ali arms with full brakes add 1 3/4" per side. i do not know if there is added distance between the trans and the inboard side of the stub axles to know which is the right length axles to use. this of course would help if i had any part in hand, but i am doing this all on your guys info so far.

johnh is brining me a setup off this weekend of a drag car to try and fit. it would be great if anyone can clarify before i head up to this show this weekend though so i can get this stuff at the swap. just seems like everyone is using a slightly different setup.

let me add that i am fine with using T1 output flanges. from what i have seen, it is all a matter of degrees and i do not plan on beating up my tranny too terribly bad. so if using T1 flanges, what do i need to go out from there to the stub axle?

Yes, Wally, the 86 944turbo axles are longer than the T1 axles.
From what I understand, correct me if I'm wrong, using the 86 944turbo aluminium trailing arms,
1. use either the 86 944turbo axles with the cv joints( 100mm) and with the 181 output flange at the transmission,
2. T2 bay window axles with cv joints ( 100mm ) and with the 181 output flange at the transmission.
Think its more difficult to mix and match 2 different cv joint sizes (ie, 90mm T1 and 100mm T2 or 944 or 912,914) on the same axle.

Cheers.:)

Here is what I would do:

IRS Tranny > T1 output flange > T1 CV > long 944 axle '87 up > T1 CV > T1 stub axle

* From my understanding the T1 and T2/944 CVs are interchangable on the axle splines. I hope so as I have assumed this in my conversion, but not had the chance to mock up the axles on the T2 CVs... Granted I am 99.9% sure it will work.

The dia. of the axles are different. The 86 944turbo axle dia. is 27mm, the dia. of the T1 axle is 24.4mm. I don't know if the T1 axle will fit the 100mm cv joints (ie T2, 944...). as there is a difference of 2.6mm! What say you guys?:)

The dia. of the axles are different. The 86 944turbo axle dia. is 27mm, the dia. of the T1 axle is 24.4mm. I don't know if the T1 axle will fit the 100mm cv joints (ie T2, 944...). as there is a difference of 2.6mm! What say you guys?:)

we are heading in the right direction. i wish i could be of more help by being able to have parts in hand. i will soon. should be getting some this weekend. i like pillow's idea if it works just because i am able to reuse so much T1 stuff and keep it cheap and still strong enough.

Don't you think that using an aluminium trailing arm, you want to use bigger and stronger cv joints and axles, especially one with a big engine and also going through all the effort to use the wider trailing arm? :)

i don't see the corelation to wider ali arms and beefer CVs, but i do with a bigger engine. no one has demostrated a real NEED for it though. many drag racers are pumping much more HP than i will be and still use T1 stuff all the way through. i have no problem bumping up if it is needed, but i am not hearing that so far. also no reason not to do it if you want though.

given, 951 brakes aren't really NEEDED, but they have a visiual wow factor at least.

Ok, here are some measurements, 86 944turbo axles: dia:27mm length 540mm, T1 axles: dia 24.4mm length 420mm. (+/-1-2mm):p . I don't have the T2 measurements but would say close to the 944 axles specs.:) .

Oh yes, the 86 944turbo trailing arm's stub axle uses 100mm cv joints and cannot be interchanged with 90mm stub axles so unless one can find an axle shaft that accepts 100mm cv on one side and 90mm on the other, to be use with T1 axle flange at the transmission, I don't see how on e can use just the longer axle shaft with wider arms and still use 90mm cv joints.:) Correct me if I'm wrong or any other suggestion?:)

Gentlemen,
The 944 turbo axle has porsche pline pattern, the VW T3Bus/Vanagon axles have VW spline pattern, thus allowing 100mm VW CV's on one side and 90mm Type 1 CV's on the other side. I've run them now in that configuration for two years, so yes, it works fine and I agree with Zen, that you are more likely to break your trans - even if it is reinforced - first than you will break a 90mm CV...
So, the Vanagon axle has the right length for a 944 turbo alu arm and a type 1 trans.
Good luck,
Walter

Thanks Wally for the enlightenment.:)

GREAT. glad you had the answers. so let me go for perfect picture clarification. from the tranny:

T1 output > T1 CV > bus axle > T2 CV > 951 stub

question: any particluar years on the T2 axle and CV or any year? helgesen just handed me the setup for above to test fit, but we are not sure which axle, T1 or T2 is on there. i will measure ASAP.

Zen,
I used a Vanagon (a T3 bus model) axle.
By coincidence I have the axles on my workbench, because of the 915 trial fit :-) They measure about 54,5-55cm length.
Hope you can find the right ones with this info.
Greetings,
Walter

the car is off to buffing and interior. so time to start concentrating on this. yetibone happens to have access to a T3/Vanagon with axles and CVs intact (condition unknown though). looks like those are my key.

so after rereading all of this and without being able to mock this up until my car gets back, i am understanding needing the following to get the 951 trailiing arms onto my '73 standard bug:

tranny > T1 output flange > T1 CV > T3/Vanagon axle > T3/Vanagon CV > 951 stub axle

can you guys validate this? considering:
1. spline mating
2. bolt pattern mating/CV size
3. proper length to cover the increased track
4. anything else i am not considering :D

also, i am trying to compile all of the measurements for us. i am only lacking a few things. i will get the T3 Vanagon CV and axle numbers when i get those parts. if anyone can post the axle diameters for T2 and T181 (if it matters or is any different), i would appreciate it.

Hi Zen,
What's up? All of the above is correct, as I have stated now more than once.
Don't you believe me? :broken:

Really, don't worry about it; Just measure the CV diameter and axle length to be sure (European and North America parts may differ) before you purchase the parts. I have that exact combo under my car for 3 years now. Its fine.
Cheers,
Walter

not questioning you wally. looking for assurance that i understand it all correctly. i am unable to do measuring and fitting since i am not at a point where i can start fitting up the arms yet. and when i get my car back, i only have 5 weeks to get it all together. :( :eek: also, i do not have some of the parts readily available. thanks for looking it over and keeping it in line.

another thing i wanted to accomplish was a clear recap so someone just hitting the thread for the first time can see the results without having to dig throught the whole thread to figure it out. i will try to pull together a tech article on all of this as i get it on my car.

Haha, of course I understand Zen. I would want to know for sure also when purchasing s/th not stock or yet done by many.
Looking forward to the tech article.
I am curious what your solution will be for adapting the (inner) rotating point of the alu trailing arm, since you can obviously not use that very big (17mm?) allen srew of the bug.
Good luck,
Walter

Wally,
I'm under the impression that the inner bushings just need to be removed and type 1 IRS bushings installed. I haven't put my early alloy arms on yet so I'm learning also and looking forward to the tech article too.

Nick

Yes, that would be the most elegant way. Never actually seen it that way, but then again, not many drive with these arms anyway :-)
Back when I did the mod, I imitated the original way the arms rotate on the porsche 944 by welding in a large sort of nut with thread inside, so I could use the porsche bolt. Its a bit more complicated then I can describe tho.
Greetings,
Walter

well after all of that, i ended up with the wrong parts anyway. Yeti pulled some axles and cv's off of a Vanagon (have to check year again...i don't remember) for me and they are the same dimensions as the bug. they are 90mm cv's and the same axles length. they are, in very rough measurement, about 3.5-4" too short.

doh...and i am tight for time. time to go on the search again. i am reading back through all of this again to check my options and verify if i have the right parts to what is listed above. T181 outputs are NOT an option at this point. so i have to find something workable with T1 output and 951 stub. back to reading.