924Board.org

[Herr-Kuhn]

Greetings.

Time permitting I have been pecking at my 924-Audi AAN turbo conversion project. Somewhere between building many turbo 928s and my Audi AAN powered S4 sedan the 924 project was put way on the back burner...but I'm now doing a little work on it.

We have a donor 016Y transaxle and the G31 transaxle. Here are my plans:

Use G31 as basis for build
Install Quaife
Swap 3rd and 4th gears from 016Y into G31
Replace dogs/syncros on 1st, 2nd, 3rd.

Can anybody tell me are there any pesky details to pulling this gear swap off? The problem with the G31 is that 3rd and 4th are too short for good use of my powerband. I have my Quaife and the 016Y is apart in pieces with the syncros, dog teeth and mate gears zip tied in bundles.

I just need to score down the dogs and syncro rings for the rebuild and want to make certain I have it all before I go ripping into the G31. I realize 1st gear on G31 is different than 016Y, but I'm under the impression that the 2nd-5th gear sets can be interchanged. 5th actually has the same tooth counts on either box.

Thanks,

JK

[ideola]

What is this going in to?
_________________
erstwhile owner of just about every 924 variant ever made

[Herr-Kuhn]

1977.5 924. Will be grafting in the supports for the trans (I may hang from chassis, not certain yet) and running the later cast swing arms (those mounts will need to be custom as well) with the early torsion bar tube (mine has no rubber mounts like 1978 and later do).

I have bell housing and torque tube that go with this trans and we will mate them to the inline 5 AAN. It's a very deep project for sure, but should pay off upon completion. I don't have a lot in these trans but wanted to go this way instead of with 951 or 944 Audi trans as these are stronger and lighter...just crappy ratios on 3rd and 4th. Keep in mind, my RPM range will be to like 7,500 with this engine. The spacing between 4th and 5th was waaaay too large.

Do you have any data in interchangeability on those gear sets?

[Cedric]

Doesnt the euro version have a lower 5th, would make the gap smaller.
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1980 924 Turbo
www.instagram.com/garagecedric/

[ideola]

3rd thru 5th gears are all interchangeable between the 016Y/Z, the G31, and the G15. R, 1st, and 2nd are not.

If you are intending to use the G31 as the basis, and you have the G31 torque tube, you should be in good shape to do what you describe. Just be aware that the nose cones are NOT interchangeable. You must use the entire case and everything from the G31, and swap the desired high gears into it.
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erstwhile owner of just about every 924 variant ever made

[emoore924]

[v8carreragts]

G12+ 915

Correction, 3rd is not interchangeable with the 915. 3rd has the same size synchros as 2nd. The shift sleeve slides between 2nd and 3rd.

The euro has a .706 5th (same as 016Y) vs the US .600 (same for 016Z)
_________________
84 944--924 Carrera GTS clone w/520HP Chevy 302 V8--RUNNING!
2015 AUDI Q7
2013 Dodge Charger R/T AWD HEMI
2013 Chevy Cruze

[Herr-Kuhn]

Yes, the goal is to use the entire G31 as the basis. I would like a taller 1st gear, but that is not an option as the gear is on the main-shaft in that box. I want the larger input shaft on the G31 Since 2nd is not interchangeable I am stuck there, but was wanting the G31 2nd anyway because that is closer to the shorter 1st. It's really not an issue as 1st will just be used to get the car going...the big power gears will be 2-4th and this engine and turbo setup should deliver it in big piles of torque through there.

So, are the syncros, and dogs between G31 and 016Y completely swappable between 3-5th gears (between boxes, not gear to gear)?...in other words can we visually inspect those parts and select the best ones? I know I will at least need the syncros for 1-3 and dogs on the first 2 gears. Both 1st gear dogs are hammered...people always downshifting into 1st...quick way to hammer up the parts.

As far as ratios...I looked at the 8:33 gear set but finding this is hard and the AAN can easily go 7,000 RPM so I don't know that it's necessary or even wanted (might be too tall). At redline the 7:33 puts me out to over 180 MPH...way more than a narrow body 924 will ever go with me driving. With the 8:33 it is like 210 MPH. Shift points land me in the next year at around 4,200-5,000 RPM....perfect for a medium to large turbo with a wide power band.

I don't build anything as a dyno-queen. My goals on this car are 30+ MPG and about 400 HP on the axle and under 2,700 lbs complete. 0-60 in 4 second range with 11.5 or so quarter mile and handling to boot. Basically run like my twin turbo 928s but be hauling around 1000 lbs less.

[v8carreragts]

The dog teeth on the G31 1st gear only fits a G31 1st gear. 2nd and 3rd are the same between all snailshell boxes. The synchros from the 928 can be used for 2nd and 3rd. 4th and 5th are 915 parts -- you can use any 915 ratio here. The 4th and 5th synchros are 915 parts.

The 8:33 isn't that difficult to find. I have one in mine. I just bought a G31 from the UK.

The problem with the US 5th gear is it causes the engine to run at too low RPM's at highway speeds. I used the Euro ratio.
_________________
84 944--924 Carrera GTS clone w/520HP Chevy 302 V8--RUNNING!
2015 AUDI Q7
2013 Dodge Charger R/T AWD HEMI
2013 Chevy Cruze

[Herr-Kuhn]

I plotted out the gearing charts on this G31 with 016 3rd and 4th gears and I get the following at 7,000 RPM with 928S4 wheels and tires:

1st 34 MPH
2nd: 61 MPH
3rd: 98 MPH
4th: 135 MPH
5th: 181 MPH

Seems this looks pretty good. Cruise at 5th at 65 MPH is 2,500 RPM and at 80 MPH is 3070 RPM. If I dropped a 8:33 that would bring the rpm down 14% at any given speed. I'm thinking I can select a turbo that feeds on real strong at around 4,000 RPM. We may do a mini-twin turbo on this setup due to the space constraints and just to do something a little different.

Seems these ratios should work pretty well with the 2.2 inline 5. I don't want the RPM too low with this small an engine off boost. Also, 7,000 is conservative as I should be able to go 7,500 RPM easily...with that this makes the speeds:

36
65
105
145
194

This car will likely never see the north side of 140-150 MPH. The goal is to make them tall enough to work well with the turbo but not so shallow that all I end up with is wheel spin. We're looking to have somewhere over 400 HP on the axle on this, thus the reason I'm going G31 on the box. Saw some AAN powered 924S cars with blown out Audi boxes (weak ring and pinion, specifically after they wear). This car was either destined to get G31 or 951 box. I tend to like the dog-leg box a little better since I'm used to it from the 928s...plus I scored down both boxes and the torque tube for $500.00. The Quaife was spendy, but I should not be too horrible on money into this trans upon completion.

The 915 LSD is not the same because the G31 uses a different spline on the output shafts than the 915 does.

[v8carreragts]

[Herr-Kuhn]

I received the Albins dog teeth for 1st and 2nd this weekend along with the pistons and rods for the AAN rebuild. There is much work to do but I hope to score down the syncros I need to complete the box head to toe in the coming 3-4 weeks or so. Nor sure if I will do 4th and 5th, but 1-3 are for sure going to get done. I suppose whilst it is open best to go get them all. I don't like doing jobs twice.

My Quaife matches the factory stub shafts on the car and I will likely just use those for this build. Since we're using the same ring and pinion he will just be setting up the ring gear with necessary shims. I've asked him to paste the gears before it all gets torn down to check the hit between the gears.