Is Transaxle alignment OK?

[Colin Fabri]

I have trial fitted a 302 engine into my RCR40 chassis and when positioned all the way forward, I measure the G50 transaxle centres to be 200mm (8 Inch) from bell housing. By running a string line between the centre of left and right wheel hubs I calculate the gap is 15mm (approx. 5/8 inch) between transaxle centre and wheel hub centre.

To align perfectly I need to slide engine forward the 15mm however this will require modification to the firewall. So the question is to find out how critical this alignment is and to see if it justifies the firewall modification.

I know a wheel would move more than 15mm as vertical travel up and down so my logic says this horizontal misalignment is OK, but as I am about to drill the chassis for engine mounting, I would like to check first !


Appreciate any assistance
Colin

 

[ali grey]

Hi Colin,
I believe you require all of that misalignment so your cv joints do not operate in one spot internally,i think my car would have close to 30mm.you could search to see if you can some photos of drive lines.

Cheers Ali

 

[Randy V]

I have a shortened G50/03 and moved the whole mess a lot further forward than that for multiple reasons, the compound angles that the driveshafts were only one consideration - the rest was getting all of the transaxle to fit inside the body work. Had I not moved it forward, the shifter mechanism would have been hanging out the backside of the bodywork.

While I have not updated my blog in a very long time, I did take pictures and measurements in the hope that I could document my journey in order to help others going through the same.

driveline Mounts

Of course by doing it this was, you will either need a sizeable lump in the firewall like most GT40s have, or you may end up looking into a much shorter water pump like the Ford Explorer had or an electric remote pump like I and a number of others have chosen.

Also trying to fit a starter in any orientation was not what I would have called a breeze..

It was at this point that I relialized that I was not dealing with a kit-car as I was left up to my own resourcefulness to make it all work. There are more solutions available now for things like the starter, but your still on your own for how you're going to handle the cooling system..

Good luck!

 

[Robert May Eng.]

I have a shortened G50/03 and moved the whole mess a lot further forward than that for multiple reasons, the compound angles that the driveshafts were only one consideration - the rest was getting all of the transaxle to fit inside the body work. Had I not moved it forward, the shifter mechanism would have been hanging out the backside of the bodywork.

While I have not updated my blog in a very long time, I did take pictures and measurements in the hope that I could document my journey in order to help others going through the same.

driveline Mounts

Of course by doing it this was, you will either need a sizeable lump in the firewall like most GT40s have, or you may end up looking into a much shorter water pump like the Ford Explorer had or an electric remote pump like I and a number of others have chosen.

Also trying to fit a starter in any orientation was not what I would have called a breeze..

It was at this point that I relialized that I was not dealing with a kit-car as I was left up to my own resourcefulness to make it all work. There are more solutions available now for things like the starter, but your still on your own for how you're going to handle the cooling system..

Good luck!

Your doing a bit of head scratching then Randy. While you are re engineering the engine bay is it not possible to lower the engine a bit more? That might allow the engine to go forward without encroaching on the interior of the car. Also what type of gearchange are you using?

Bob

 

[Phil]

Colin:
Having been thru this also a few times, I can appreciate the dilemma.
As Randy mentioned it is a process that requires some careful thinking and planning, and a 1/2" spacing in the wrong place will make fitting some components difficult or impossible, especially with fore and aft engine placement.
Even with a short water pump, or no pump on the engine there is an issue on some chassis with the lower pulley, and thru chassis water tubes. The shift linkage also comes into play especially on left hand drivers, and moving it may require more u-joints and a bit more flex and a less than positive feeling.
I just went thru a whole "pull the motor and gearbox....re configure chassis and motor mounts...and re set shift linkage debacle" because of a 5/8 or 3/4" issue with the gearbox interference. All is well now, but the trade off was a slight angle in the CV joints which I didn't consider a problem and frankly was necessary to solve the problem.
These chassis, among others, are an exercise in packaging, and planning is essential so look at a lot of photos and ask a lot of questions.
Modern CV joints are made to work and deliver power in some extreme angles, especially the outers as is evidenced by most front wheel drivers, and they regularly go the life of the vehicle, usually going bad because of a corrupted boot seal, or accident damage.
Getting the motor placed correctly and having some angles on the halfshafts is no big deal IMHO.
Cheers
Phil

 

[Randy V]

Your doing a bit of head scratching then Randy. While you are re engineering the engine bay is it not possible to lower the engine a bit more? That might allow the engine to go forward without encroaching on the interior of the car. Also what type of gearchange are you using?

Bob

I had thought of lowering it more, but it was already pretty low. Actually the bottom of my oil pan is 1/2" below the bottom of the car and I'll be engineering a sacrificial skid plate to help protect it...
I have a cable shift system originally manufactured by Cable-Shift and modified by me so it would actually work with the transaxle I have.

Yes CV joints - like Universal joints actually need to have offset angles to work with or the load carrying surfaces never change/rotate and the lubricant is not evenly dispersed inside. There are potential critical angles, but I truly believe that we would not see those angles in most of these cars. The rest is packaging and esthetics, if you think a compound angle may be fine for the service range of the CV joint, but look terrible - then it's at construction time to break out the pencil and paper to re-engineer the whole mess..

The bottom line in my opinion is that these cars have to be built through a series of compromises. Even the originals had some of this.
I suppose that the manufacturers of these cars are doing us a favor by giving us the latitude of using various transaxle configurations and engine positions which will "work for us" rather than being a fixed "square peg in the square hole" process you would expect with a true kit.
This is also a key reason - I suspect - that many kit builders lose some of their momentum. In some cases, all momentum.

 

[Colin Fabri]

Guys, thanks for all the helpful replies. Sounds like I need to purchase and trial fit the gearbox and starter before I start drilling mounting holes for the engine.
Anyone know of any G50 short tail boxes for sale? Real hard to find any for sale in Australia.

-Colin

 

[John]

Give Chris [ Flatchat ] a call, he has a couple of boxes under the bench I believe. and he's not that far away, only out at Warwick.

cheers John

 

[flatchat(Chris)]

Historic car racing is on at Morgan Park (Warwick) this w'end --well worth the visit and I need to to talk GT40 stuff -- with any body

 

[Cliff Beer]

Colin,

There's quite a few short tail porsche boxes available in the US here - this might be the place to look. I know my UPS guy will ship a crate up to 200lbs anywhere in the world, and you might be able to slip under that with efficient crating.

Alternatively, I believe the short tail rear cover can be transplanted as I recall. Not absolutely positive on that to be honest however.

As far as CV alignment goes, 15mm is good. That should be somewhere around 7-8 degrees, right? My CAV was similar in alignment....that was as far forward as I could get it as the dizzy was right up against a cross bar on the bulkhead at that point.

Good luck!

 

[Randy V]

If you look in my blog, I tell you how to shorten the longer housing to be within the same (or extremely close) dimensions as the short housing:

Transaxle & clutch

I hope that helps!