Hybrid Axles (930/915), Will it work?

[mbaran]

I've got a '70 911 that's getting a 930 trans installed. The car had a 915 in it, so it has the 915 axles in there now, with 4 bolts and 2 pins.

It's getting a 930 (1979, long bell housing) with 6 bolts, no pins. The axles with CV's are identical in length. Here's my question

Is it possible to use the 930 axles, but to place a 915 CV on the wheel side of the axle? As far as I can tell, this would work, but I'm curious for someone who's done this.

Would it make more sense to just use 930 complete axles and have two pins pressed in, then use 4 bolts?

Thanks!

[Grady Clay]

I don’t know the answer but would like to find out.

First, measure the distance between the axle flanges on the 915 and the 930.
I think they should be the same.
You will need to make some large “C” calipers – like for measuring wheel rim width.


You cannot use a 930 Turbo axle assembly. It is too short.
The difference in length is due to the dual tapered roller wheel bearings in the 930 rear arm.

Your 4-point ball bearings in your 911 arm allows for the longer axle assembly you have.


Here is the question:
Will a 930 CV joint internal splines fit a ’69-’71 axle shaft?

If so, all you need is a pair of inboard CV joints – type 930.
The axle and outboard CV joint can remain the same.
A ’79 930 uses a CV joint (inside) gasket so you will want CV joints that use the gasket (no end cap).


Another possibility is to drive out the 10 mm roll pin from your existing CV joint.
You will need to ream the through hole to 10+ mm to clear the M10 bolts.
You can drill the tin boot cover and add the necessary hardware.
The ’70 CV joint uses a different (outside) gasket (with relief on the CV joint) from the 930 (inside) gasket (with relief on the flange).
This may present a problem of too little metal-to-metal contact between the flange and the CV joint.
Carefully inspect this.
It is the metal-to-metal contact shear that transmits the torque, not the shear in the bolts.
The bolts only provide the clamping force.

Best,
Grady

[mbaran]

This is all good information. Seems the best case scenario would be that the Inboard 930 CV will slip onto the 915 axle.

If not, there seems to be a bit of modification to be done, hopefully there's a reputable CV/Transaxle shop in the Los Angeles/SoCal area who can assist with something like this.

Thanks, hopefully someone else can chime in with more info!

-Matt

[lin7310948]

you already have the aluminum trailing arms. you are doing a LS1 swap i believe...i use 85-89 carrera axles and cv joints. these are the axles with the different outboard cv joint and i believe the same as a turbo inboard cv. these have held up very well.

[mbaran]

Originally Posted by lin7310948

you already have the aluminum trailing arms. you are doing a LS1 swap i believe...i use 85-89 carrera axles and cv joints. these are the axles with the different outboard cv joint and i believe the same as a turbo inboard cv. these have held up very well.

I don't believe I already have the aluminum trailing arms. The car is narrow bodied with SC flares and 964 wheels, so the rear suspension is "stock" to a '70.

On that same thought though, would it simply work to move towards the one piece 85-89 axles with stubs? Or is there a difference in wheel bearing design that would make this not possible?

[lin7310948]

i was looking at you rear suspension welding and i thought that the trailing arms were aluminum. if not, i would get a set and not use the 70 steel ones..

[mbaran]

In the interest of not tearing apart the whole rear end and keeping this project moving, I'm open to other suggestions too!

[lin7310948]

i looked again and the first picture shows steel and the second shows aluminum. as i said above it might be easier and stronger to use aluminum trailing arms which are very reasonably priced. i do have 930 rear disc and calipers on my trailing arms.

[jpnovak]

Your question has some complications. The 915 had both early style (4-bolt, 2 pin) joints that were 108mm and the later 100mm (6 bolt ) joints. The later style have a smaller shaft diameter and corresponding spline section where the CV joint mounts to the shaft.

The 930 should have a 108mm -6 bolt pattern. Yes, the dimensional length of these axles should be the same.

I suggest that you find the early axle shafts for the 108mm CV joint. They will bolt right into your hubs and they use the same bearings independent of a steel or aluminum trailing arm. This way you can use the early style 108mm outer joint (4-bolt, 2 pin) with the 930 108mm inner joint (6 bolt). I think the axle diameter is the same.

I had similar issues swapping from a 915 to a type 911/01 in my 71 track car. The early transmissions used larger joints and CVs compared to some of the 915 boxes.

[mbaran]

Originally Posted by jpnovak

Your question has some complications. The 915 had both early style (4-bolt, 2 pin) joints that were 108mm and the later 100mm (6 bolt ) joints. The later style have a smaller shaft diameter and corresponding spline section where the CV joint mounts to the shaft.

The 930 should have a 108mm -6 bolt pattern. Yes, the dimensional length of these axles should be the same.

I suggest that you find the early axle shafts for the 108mm CV joint. They will bolt right into your hubs and they use the same bearings independent of a steel or aluminum trailing arm. This way you can use the early style 108mm outer joint (4-bolt, 2 pin) with the 930 108mm inner joint (6 bolt). I think the axle diameter is the same.

I had similar issues swapping from a 915 to a type 911/01 in my 71 track car. The early transmissions used larger joints and CVs compared to some of the 915 boxes.

I have both sets of shafts. I have a set of shafts that are 4 bolt 2 pin (which im guessing are 108mm?)

That being said, Can I use those shafts, with outer CV's for my existing car, and just get new 930 Turbo CV's for the trans side, and be all good? My car now has the 4 bolt 2 pin shafts for the wheels.

-Matt

[Flieger]

The Aluminum trailing arms are not a simple bolt on for a 70 or 71. The rear damper has a different geometry on the cars that use them. The rear crossmember changed in 72 onwards so they can use them no problem. On a 70 or 71, they make the damper further out and back. The damper can rub on the inside of the damper tower where it goes into the crossmember. It can also rub on heat exchangers. You can fix this by either getting a new crossmember, machining the Aluminum arm where the damper attaches, or use a rubber dust cover and make the suspension stiff so it does not move much. The machining involves milling down the boss where the damper attaches, through the hex part of the steel insert, then threading to retain the steel insert where the damper attaches.

The bearings and hubs are also different on the Aluminum arms.

Some people with hot rod 911s, lowered with stiff torsion bars, and using headers, do not have a problem that connot be cured with the rubber boots. The suspension can still bind at larger displacements, however.

[mbaran]

Yeah, i don't plan to swap them out. Ive already swapped to a custom coil over suspension.

[euro911sc]

Are not the half shafts different? I believe the turbo shafts have 28 splines and my SC's, at least, have 25 splines on the end. My info is patchy and put together from weak memory, but you may have an issue there when trying to swap CVs around.

-Michael

[mbaran]

I guess that's what im trying to figure out. I'll probably just go out into the garage and count later, they're just so damn greasy.

[mbaran]

So it seems they're both 28 spline...

[mbaran]

bump!

[dad911]

It was a long time ago, but I put a 915 in a car that was previously set up for a 930. I believe we just swapped the stub axles on the transmission.

[mbaran]

anything?

[euro911sc]

Looks like you are going to have to find out for the rest of us

-Michael

[sirhiss]

Hello
I have just solved this problem on my 915 gearbox with 930 stub axels, i am using the old driveshaft from 72- 108mm and i have removed the dovels from the inner gearbox part of the driveshaft and then i have cut a 10mm bolt so it just extends 12mm out from the 930 stubs and it goes in the dovel holes, cheap and easy. Use bolts grade 12.9 as original. Good luck from Denmark