901 Output flanges

[GS guy]

Lurker here, but regularly follow the site to keep up on the latest true performance VWs. :)

Like many here, while fitting a 901 trans into my car I ran across the problems of CV joint sizing, axle issues, stub axle, etc. I'm going Suby power so need the added beef of T2 CVs, but didn't want the weight, expense and overkill of going full 930. Of course the problem - one can't typically fit a T2 CV to a 901. The available output flanges are either T1 size or 930 that I've been able to find, and I have both. The solution: an adapter flange fitted to the 94mm (T1 sized) 901 output flanges that takes a T2 CV! In conjunction with slightly shorter axles (~1/2") and thing or 944 stub axles, you have adequately sized and readily available hardware for the job at hand. I've been talking to Todd at Precision alloy (the guys that make the TF-1 aluminum HP T1 engine case) and he's up for making the flanges, he's also familiar with the Porsche output flanges and produces special stub axles and T1/2 trans output flanges for HD use.

Since I've read about others having the same CV problems as me, thought you guys might be interested in these adapters. Sure solves a lot of problems!

Cheers,
Jeff

[jhelgesen]

I'd be interested in the adaptor flanges since I'll be using a 901 tranny and 86 844t rear arms in the 71 vert. Any idea of cost?

[GS guy]

Not totally sure on final cost yet jhelgesen, but according to Todd they should come in around $100/set - give or take.

I'll post updates as the project comes together.

Jeff

[LOAF]

jhelgesen and GS,

I think I am in the same boat.. I have been trolling the tranny area, but becoming more and more confused..

I finally got around to dropping the engine and tranny and am in the process of sourcing the Type IV and 911 (901) tranny.. this is going to be coupled to a late 944 aluminum non-turbo setup.. I know I will be having a problem with shafts and output flanges.. but I am hoping that there is a simplier solution then a custom piece..

Is the only reason the weight and strength to deal with a scooby engine.. (god knows that is a beast, I have modified WRX.. )

If weight wasn't an issue, how would this be done.. Maybe you can help me figure this out..

What output flange (that would go the 901 (911) Tranny)

Which Axle (stock 944 or other)

Which stub axles ( these are the ones that the brakes/hub go on.. ) sorta still learning the lanquage so please bear with me..

I which I had the knowledge to make a chart of what combinations have been know to work but I throw it out as an idea to the more seasoned builders.. Excel would work for me :)

Something like the following:

Type I tranny to Type 1 IRS
Tranny Flange X, Axle X and Stub X
but expand for the following..
Type I Tranny to Early 944 IRS
Type I Tranny to Late 944 IRS
Not sure if 901 (914) vs (911) will differ
901 Tranny to Type I IRS
901 Tranny to Early 944 IRS
901 Tranny to Late 944 IRS
and lastly
915 for the hotrods..

I know alot of has been talked about but it is hard to follow on the threads, specially if you new to this.. As well as alot of hard work, if we can capture it and pin it, it could be very useful..

Just a thought..
ALex

[GS guy]

Old thread, but I didn't follow up as promised. Todd at Precision Alloy did complete my output stubs - and did a beautiful job I might add. FYI, after talking with Todd a bit we decided to just modify my existing output stubs insetad of fitting adapters.
Precision does high end off-road VW type work and is well versed with 930 and T2 CV sizes, as well as VW and some Porsche Transaxles. They make off the shelf output stubs for T1 & T2 trannies to take either T2 or 930 CVs. They also make outboard stub axles to accept the same - this is all common practice for HD off-road use. However, using the Porsche 901/914 trans with T2 CVs is a little off the beaten path. Porsche makes (or did when these transmissions were newer) output stubs to accept either T1 or 930 sized CVs. I also understand they did do a limited run of trannies that took the T2/T4/944 sized CVs - not sure if this was 901 (based) or 915 trans though, but 915 output stubs aren't interchangable with 901 stuff AFAIK. It's my understanding finding a set of these "rare" output stubs is like the proverbial needle in the haystack. I think in general, to get T2 sized CVs to mount on a 901 trans you either have to make an adapter, or modify the output stubs.

What Todd does is machine off the outer section of the stub, the outer portion of the flange, then presses on a new chromoly flange machined to fit on the machined register of the Porsche stub, followed by welding the two together. The new (larger) bolt pattern for the T2 CV goes through both the new flange and what's left of the old stub, offset from the original T1 sized bolt pattern - strength won't be an issue here. Todd finishes up the job with a nice new black oxide coating - the finished job is beautiful! For around $100, IMO this is really the only way to go if you want to run that sized CV.
I'm not familiar with the 944 CV, or axles, etc so not sure if this would be 100% applicable with those CVs and axles. I'm running T2 CVs inner and outer with Thing outer stub axles, and most likely SAW axles.
The step up to 930 sized CV's may be more readily doable (with OEM Porsche output stubs and aftermarket outer stub axles), but with a significant hit in the $$$ dept, plus the added weight and general (waaaaay) overkill of that set up in this application. The T2 sized CV seems much better suited for a lighter, 200-300hp car.

[LOAF]

GS thanks for the reply..

Does help.. and I probably give Todd a call in a few weeks, once I have everything on the ground..

As I mentioned my not so unique situation is the following..

I am doing the 944 late conversion with sigle piston brakes.. I have the following parts that I would like to reuse as part of this conversion..

The have the 944 Stub axles.. which I am not sure I can swap out..
The 944 Axle that is conected to the Stub..
and shortly within a week a 901 (911) tranny..

The seller has different output flanges, but for starters I am not sure which flanges to even ask for.. I will check one of the threads that BG I think started.. But man I am confused..

I am not sure what can mate with what.. If there is a simple solution out there.. I hope BG, ZEN or others are watching..
I really think we need to capture this wealth of info in a nice write up.. I would, but I don't have all the answeres..

Like I mentioned I will recheck and see if I can find that post.. I am not looking at Big Hp numbers.. 100-150 at most..

Alex

[GS guy]

One other thing regarding having Precision Alloy modify your output stubs. Todd does this work in batches - he'll do a batch of output stubs all at one time, with machine set-up, etc. Economy of mass production you know! So when he starts needing another batch of stubs, he'll do them - which may be in a few weeks, or may be 6-8 months. He most likely won't do a one-off set of stubs, unless you're really desperate and have the money to back up the immediate need! What he did with mine was modify/make them along with a regular batch he was doing, I think I waited 2-3 months to get them done. Just FYI.

As stated before, I'm not that familiar with the 944 CV sizes. OD sizes of the common CV's are:
T1 94mm
T2 100mm
T4 100mm
930 108mm

There are also differences in width of the joints, what size axles they take (diameter and spline count) and even attachment bolt size.
A must have source of CV and axle info is here:
http://www.blindchickenracing.com/How_to/CVJoints_Axles/axles_and_cvs.htm
Unfortunately he doesn't cover the 944 stuff, but I think some of it is similar to what he does measure (at least you can compare).

[LOAF]

Excellent source of info..

Thanks
ALex