Making a gearbox adapator, is this okay

[mark chandler]

Hi all,

I have now got my pile of parts together as follows:

Rover v8 engine
Rover flywheel
Rover clutch cover & 10.5" driven plate
Various rover gearboxes to supply ali bolt pattern and 1st motion shaft.
Audi transaxle
Audi clutch cover & 240mm driven plate

The rover clutch is larger but looks like it will fit in the transaxle, the flywheel will however not so what I am proposing is:

Chop front off RV8 bellhousing to accomadate Flywheel and machine flat.
1/4 steel plate bolted across this and drilled to suit Audi bolt pattern

Recover splined centre from Audi clutch, machine RV8 1st motion shaft and make a first motion shaft extension to use RV8 clutch.

Extend standard audi clutch actuator to suit.

Can anyone see any issues with extending the 1st motion shaft by 2", I will sleeve so its and interference fit on the existing item and stays true.

Cheers Mark

[Russ Noble]

Well Mark,

In the absence of anyone else stepping up to this one, here's my opinion.....

There's no reason I can see that it won't work. Two things I'd watch though.

First, will the extra 2 inches place the motor too far forward, or the driveshafts too far back? Maybe you will have to fudge both a little to make it work.

Second, welding up the input shaft should be OK so long as it is done properly by a really good guy who knows what he is doing and is used to doing these sorts of things. Of course you could do it yourself on the nothing-to-lose theory and it may well be OK. I have seen several dubious looking welded input shafts that have worked just fine!

The engineering purists here will probably disagree but IMHO it will be 100% successful if done properly.

By way of anecdote, my old TR7V8 had welded and shortened axles, no problems whatsoever, but the guy I got to do them insisted on doing the shortening as well as the welding. Always guarantees all his work and never has a failure. If he didn't like it and couldn't guarantee it he wouldn't do it.

As a further anecdote, I have several forged steel latches on some equipment that I own. They are subject to abuse and severe vibration and will break regularly. Because of the cost of new ones, I cajoled him to weld them up even though he refused to guarantee them! Over the following years none of the welded items have rebroken! This is the sort of guy you are looking for!

Hope that gives you something to go on....

Cheers

[Fred W B]

Hi Mark

Seems like a good solution. How are you going to secure the steel plate to the cut off rover bell?. If the plate was ally you could just weld it.

I even have a RV8 bellhousing in the garage and I am kicking myself I didn't think of trying that. Certainly much less work and expense that what I did, as discussed in this thread - LocostBuilders

Cheers

Fred W B

[mark chandler]

Hi Chaps,

Thanks for the replies, this is indeed a nothing to lose approach but it does seem to have some advantages to me.

Transaxle remains standard

RV8 clutch/spigot etc remains standard

I must admit Fred having pored over you notes on both this and Locost builders although highly impressed was put off with the sheer amount of work involved and cost.

As you have pointed out Russ, the weak point will be the spigot adaptor, I am starting off with a pretty weedy looking input shaft on the transaxle, at least the RV8 has a bit more meat. I am concerned that it will turn off like a carrot.

The rational on a 1/4" steel plate was simply that it will be thin, I was going to try multiple bolts into the RV8 housing but may try and track down a bit of thicker ali, undecided at present so I am going to stare at the first motion shaft a little more and cringe !


As for fitting length, I,m going to build a car around the engine/box so it does not matter, will probally solid mount so this will increase bell housing rigitity anyway.
Regards Mark

[kiwi ka]

Hi Mark
Why not try it this way, I know it cost a bit more but once the adptor ring and fly wheel are made, you are then using a standard gearbox, starter motor and a standard Rover Auto ring gear. Also by careful set up the standard Audi fork and release bearing is also utilized. If you look carefully at the adaptor ring on the dummy block and the set back of the ring gear on the fly wheel, you will notice that the fing gear runs in a recess in that adaptor. Thus the standard components make it easy for future maintenance. I have used a standard Toyota diesel high pressure plate with something like 2800psi on a performance Kevlar clutch plate. Assembly of the whole unit is straight forward and 100% accurate.
Cheers

[Russ Noble]

Or.......

What about using the whole, or majority of the Rover bellhousing and chopping the Audi bellhousing portion off the Audi box (they're a dime a dozen, right?) and finding a 10.5" driven plate with Audi splines? Weld the Rover bellhousing to the Audi box and machine a sleeve to accept an Audi size spigot brg in the back of the crank. Probably no more involved than you are already contemplating, and should look nicer. I don't think the Rover bellhousing will be thick enough to be able to successfully tap even small diam threads into for your plate.

Just a thought.

[Jim c]

Mark

If you are planing on modifying the case this the approach I have taken so if it helps all the best.

It was an MX5 That I turbo charged and the owner kept braking gearboxs.400hp at the wheels does that.
I put an RX7 ser 6 box in but the issue was the same as you have.
I had no bell housing for the engine that we had selected but we had a case incorporating the bell housing.
The ser 6 box has a bolt of b/housing.
After a lot of measuring I cut and milled the case to suit the plate with machine recesses to accept the new box.

The trick to line it all up was I made a mounting plate with holes for the b/housing dowel pins to locate on and I bolted it down on the mill.
Using the digital read out I found centre of the front bearing hole I then drilled a hole in the mounting plate that it was attached to.
I made a bar that was the diameter of the hole in the new section going to be welded on this was bolted to the mounting plate with a dowel bolt.

This is so when I cut the case you don’t lose your datum, after the conversion plate was made it dropped straight over the bar orientated and welded.
Gave it a lick on the mill and it work fine.

I did not have to extend shafts fortunately.

Jim

[Simon]

Mark,
I have a rover V8 to renault adaptor. If it's any use to you to use as an adaptor, or just for playing with, let me know, it's yours.
Simon

ps, need an exhaust?

[Fred W B]

Question for Russell, and hopefully not really too much drift.

Your flywheel looks a lot lighter than mine, what does it weigh?

Seems this thread may become THE internet source on Rover/Audi adaptions

Cheers

Fred W B

[mark chandler]

Seeing the above has got me thinking again now, great looking stuff by the way.

On Zf auto boxes on RV8's you get a spacer, torque plate with ring gear (seperate plates oddly enough) so I could maybe machine down the Audi flywheel and attach in place of the torque convertor, knock up an adapator ring and should be nearly there.

The challenge is as I see it get the face of the flywheel 3cm inside the standard Audi bell housing, small clutch though !

or

Extend the first motion shaft 7 cm out and make an adaptor that will accomadate the Rv8 flywheel and cover (had another look, cover will not fit in that little hole either).

or

Get angry with the transmission and cut the front off (make a note not to destroy the Transmission or will have to repeat things) and get welding on my Rv8 housing.

The attraction of the RV8 clutch is size + lots of suppliers so cheap as chips. Can you get a 10.5" plate with Audi centre , maybe chop out the centre of the audi driven plate and weld into the Rv8 driven plate, voila !

Will a 240mm clutch take 250 - 300 BHP ?

This will be my deciding factor because modded standard audi flywheel on Rv8 auto box front end is looking very good now, I do like cheap standard parts as no harsh action or judder.

Regards Mark

[Brett James-McCall]

Mark,
Suggest you speak to Terry at Helix (Helix Autosport Main Page) he is making my drive plate to go in my Audi 01X that will sit behind my Ford 302. It is a 240mm Organic driveplate with a 24.2mmx23T input shaft. He may even be able to advise on flywheel as well.

I'lll try and post some pictures of my adaptor plate and flywheel later.

Brett

[Russ Noble]

Originally Posted by mark chandler

, maybe chop out the centre of the audi driven plate and weld into the Rv8 driven plate, voila !

Will a 240mm clutch take 250 - 300 BHP ?

This will be my deciding factor because modded standard audi flywheel on Rv8 auto box front end is looking very good now, I do like cheap standard parts as no harsh action or judder.

Regards Mark

As you can see there are plenty of ways to skin this cat!

I wouldn't chop and weld the plate. Go to your local clutch supplier, they will have a listing of diameters and splines available. Get what you need and set your pressure plate up to suit. Easy and cheap. I would only weld the input shaft as a last resort also.

Turbo Porsches run a 240 clutch. I think they would quite easily outgun an RV8. Remember no one has ever described a Rover motor as a torque monster, the valves are too small for that.

You could chop the centre out of the Rover flexplate and bolt it directly to the Audi flywheel. Forget the spacer plate, just machine the back of the flywheel to suit the distance. You're going to want a locating lip anyway. That way you might get away with a simple, thinnish adaptor plate bolted to the back of the Rv8 that the ring gear would fit inside. Similar to Russell's.

If you look closely at Russell's photo you will see the recess machined on the block side of the adaptor plate to clear the ring gear. The adaptor plate will have to be fitted after the flywheel is in place. No problem. Hasn't he done a nice job!

Cheers

[jyrki]

Originally Posted by mark chandler

Will a 240mm clutch take 250 - 300 BHP ?

Regards Mark

Mark, in Sierra Sapphire /Escort RS Cosworth 4x4s i use std 240mm clutces.
Car weights in driving condition around 1350kg (over 2800 lbs), and with over 350hp/480-500nm they still worked fine. After that point I still use orig. cover but with 6 blade sprunged Alcon plate; working well in 2wd Sierra cossie with V6 4,0 twinturbo engine. Torque over 750nm (450-500hp), still nou problemo after 30000km.

WBR jyrki

[mark chandler]

Hi Chaps, Many many thanks for the useful advise, and very useful pictures above, I,m going the Kiwi Ka/Fred W B way but without the expense.

240mm clutch on Audi flywheel, maybe get a turbo clutch as rated at 220bhp but I,m tight so will see if what I have survives !

The flywheel is rear weighted so I will have to machine off the back and rebalance; this then goes on to a spacer that will bolt to the ring gear flex plate.

Chop Rv8 bell housing and weld a plate on then drill and cut to fit Audi transaxle.

Job done…. Okay now to put it into practice. So you will have to wait a few weeks for pictures, 18 months for it to run in anger !


Regards Mark

[Russ Noble]

Mark,

I like to keep things light, but I would tend to go 8mm or even 10mm for that flat ally plate. But that's just me, someone with an engineering background may confirm that 6mm is fine. I would be worried though about only 6mm of thread in the ally although you could always helicoil or similar.

Cheers

Edit. Why the f/w spacer?

[mark chandler]

Hi Russ,

6mm was just off the top of my head, I will see what plate is available and select something that looks suitable.

The flywheel spacer is just to achieve the 30mm from gearbox side of the bell housing adaptor to the front of the flywheel as shown, without it the the flywheel would be at least 10mm short of the first motion shaft.

If I am lucky when I machine the back of the audi flywheel I may be able to make most of this gap up so it may be irrelevent but without a substantial plate I will not be able to tap and stud the adapator ring facing the engine so will need to clear bolt heads with the starter ring.


Regards Mark

[Jac Mac]

That 30mm Flywheel Spacer is asking for trouble with a capital 'T' if the bolts go thru flywheel/spacer /flexplate, unless you are using dowels as well , even with dowels over the 30mm distance some movement could take place.

Much safer to make a one piece flywheel with the correct offsets to accept clutch then bolt / fit the ring gear to it than have the triple sandwich set up you have above.

Jac Mac