Inverting transaxles

[Julian West]

I've been admiring the engineering in the Ultimas for some time, & see the transaxle is inverted.

This is a modification I'm considering for my GT40 replica, using the Renault UN1 transaxle.

The diff can be fairly easily flipped, however I'm concerned about oil control. Does anyone know what internal mods (if any) are carried out in order to keep the oil under control & lubricating everything properly?

Thanks in advance for any information!

[Steve_D]

We have an advantage with the Porsche box in that it was originally designed to run the way we run it. Its Porsche themselves that are running it upside down
I think you turn the diff over in the Renault box not the box itself but I could be wrong.
Steve

[davefiddes]

The only mods that are made to the lubrication system of a G50 box is to plug up with breather and to fit a pair of breather tubes from the side of the gearbox to the top ex-drain plug(now the filler). The two pipes are taken to a breather tank which vents to the atmosphere. Ultima supply a pretty (and durable) alloy tank because it is usually situated between the two exhaust silencers but anything would do if you don't have to put it somewhere hot.

For details have a look at Stigs build diary (www.ultima-gtr.info) in about March.

Ultima recommends that the box is filled with 3.5 litres of oil which I believe is different from the standard fill. There isn't an oil level reference AFAIK just make sure that you put the correct amount in in the first place!

[MattYorke]

Why would you want to invert a UN1 box, it's the right way round already isn't it?

[Julian West]

The purpose of inverting the box is to improve the weight distribution by lowering the engine in the chassis.

If you look at the Renault box side on, the input shaft (ie crank centerline) is 70m higher than the driveshafts. Thus inverting the box lowers the engine up to 140mm, whilst keeping the driveshafts at the correct angle.

Flipping the diff is no problem in the Renault box. My main priority is oil control.

Thanks for the link, will have a look. I take it there are no mods made to the internals of the G50?? & Also I see Ultima use the Getrag (Boxter?) transaxle inverted??

[doc_fudge]

Julian asks a valid question...what is the 6 speed Getrag out of??

Andy

[Julian West]

Andy,

I *believe* it's from a Boxster, but more interesting (to me!) is that the box on display at the Ultima stand at the Racing car show was definatley inverted.. I have a picture somewhere if anyone's interested.

I'm sure it's inverted for the same reason, ie to lower the engine in the chassis!

[Stig]

Julian West said:

Andy, I *believe* it's from a Boxster, but more interesting (to me!) is that the box on display at the Ultima stand at the Racing car show was definatley inverted.. I have a picture somewhere if anyone's interested. I'm sure it's inverted for the same reason, ie to lower the engine in the chassis!

Err... no.

The reason that the 'box is inverted is that otherwise you'd have 5 (or 6) reverse gears and one forward!

Remember, in a Porsche the 'box sit in front of the engine, in an Ultima, it's behind.

[doc_fudge]

Agreed.

But does inverting the 'box cause the input shaft to be lower or higher than when the 'box is used "right" side up?

I thought Ive read about this somewhere else. Does anyone recall?

Andy

[MattYorke]

The Renault Alpine GTA used a rear mounted engine configuration, although I don't know whether they inverted the box or flipped the diff round to make it work.

>> Edited by MattYorke on Monday 4th August 12:56

[msv]

The 6-speed Getrag as used in the Ultima is that of the 996 C2.

[gtrclive]

MattYorke said:

Why would you want to invert a UN1 box, it's the right way round already isn't it?

Not in the Renult Alpine coupe it isn't. They are rear Engined, like a Porsche. But you lust take the gearbox apart and turn the diff around in those boxes, I did it and fitted one to my GT40.

>> Edited by gtrclive on Monday 4th August 19:59

[Julian West]

The diff is flipped in the Alpine as opposed to the R21T, but the box is still used the same way up. The facility to flip the diff means inverting is easier!

FWIW the ZF DS can also be inverted.

So if it's definatley the case that both types of Porsche transaxles are inverted for use in Ultima's, can anyone give a definitive answer with regard to oil control??

[JulesP4]

Just a quick question, does anyone know if the early Boxster 2.5 manual diff can be swapped around so the gearbox can be ran in a rear engine configuration?

Thanks

[ezakimak]

JulesP4 said:

Just a quick question, does anyone know if the early Boxster 2.5 manual diff can be swapped around so the gearbox can be ran in a rear engine configuration?

Thanks

No

Well not easily, I think you will find it’s a hypoid set up. So you will need a new crown wheel and pinion.