ZF type LSD for UN1/UN5

[Stephane Goria]

Gentlemen,

We recently engineered, for our cars, a ZF type LSD for the UN1/UN5 gearboxes.

It is an LSD with 2 friction discs by axle, so 4 for a whole differential with 8 friction surfaces.

It is build with the 4 spiders configuration and use the OEM diff housing. It was our main concern as ZF type LSD usually do not allow to use all crowns available for these gearboxes.

Also, we wanted the cost to stay the lowest possible, as we don't sell parts, and only make parts for our own use.

One of the very interesting feature is that it can be adjusted from outside : I mean you can set up your own internal friction pressure (with even a different pressure for each planetary). This is basically usefull as every car has a different weight, different suspensions settings, different drivers too....and also according to the track you are going to race.

We are going to produce a first batch of 10 for our cars & friends here in france. I wondered if there coud be any interest of forum members for this LSD.

The price would be around 590-620 gbp based on a core exchange. We would need back the original diff in full (without the crown obviously).

If any interest is manifested and confirmed, we could add extra production to our run.

Also, obviously, and according to the forum rules, I would before, in such case, change my personal status to "seller" and bring my financial contribute...:angel:

Cheers

Stephane

 

[PhillipM]

Hi Stephane, have you sold any of your units to the Rallyes TT's guys? Would they be reliable under the stress of off-road rally use?
I've currently got Gripper looking at building one for our UN5 equipped rally car, but if you already have one made/designed it's worth a look.


Is it possible to run different ramp angles for acceleration and deceleration?

 

[Stephane Goria]

Hello Phil,

No, this LSD is only existing on CAD at the moment...

The 4 spiders diff already run with offroad cars with no probs, but you should already know this if you run UN5 as it is OEM build with a 4 spiders diff.
Anyway the main problem with the UN5 is the rear bearing of the primary shaft wich is too weak : 52x25 is clearly not enough for the torque inputed.

Have a new one on my bench now with this failure and unfortunately the damage is so big that it ruined the gearbox housing.

For the LSD project, we keep spiders, planetaries and housing with very little modifications on housing and planetaries, so the global strength is not affected.

The new point will be the heat dissipation under very hard use and preload. We made some choices, we will see how it goes...and I have friends here with heavy feet, so no doubts they will do the right testing...

Maybe for very hard use, we could tap the diff and keep it filled with its own oil, gonna see...

The friction surface is 280 mm2 by axle , so 560 mm2 per diff.

With the current configuration, only the preload is adjustable, but it is adjustable from outside the gearbox wich was a feature we looked for, to avoid having to open the gearbox to chnage settings.

Unfortunately, using the original housing brings some benefits like reducing cost but brings some constraint as the lack of room.

So actually, our engineering is limited to a clutch friction type (preload) and no acceleration/decelation evolutive pressure (ramp angles) is possible.

To give you more details, the room remaining to install such feature (ramp angle) is 14 millimeter located at the center of the diff between the 2 planetaries, so if you have any idea it is welcome. We had some thinking but we saw no ways...unfortunately.

Greetings

Stephane

 

[PhillipM]

We already run a ceramic input bearing, but it tends to be the pinion + crownwheel we ill from the shock loads back through the transmission, if it's preload only it would be quite highly set for us, so I see what you mean about heat problems.

I'll have a think about it first.

 

[Stephane Goria]

Also,

One of the cost raiser is machining. I have my parts machined in the US for various other gearboxes project as in the US you can find some great people loving to mill and to produce nice parts where, here in France, forget....

But the problem with the us machining is that it is submitted to custom taxes and VAT when entering EU, and as these taxes are applied on the cost of the part+shipping...it drastically raises the cost...

Cheers

 

[Stephane Goria]

Forgot last words...

It drastically raises the cost for nothing...just bringing a financial contribute to King Sarkozy wich makes me puke twice...

 

[PhillipM]

:lol:

I don't have that problem, got a CNC mill and lathe in the workshops