ZF LSD power handling

[Cuz]

Hello all - apologies if this has been posted in the wrong section, happy for it to be moved if need be.

I was just wondering what people's experience with the ZF LSD has been? I'm especially interested in the power handling abilities of these units and if there are any unusually weak component in them.

Also, where are most people sourcing these units? I'd also like to see what people's experiences with the 80% lock upgrade is and where the upgrade was purchased from.

Looking forward to your replies.

[kwilford]

Originally Posted by Cuz Hello all - apologies if this has been posted in the wrong section, happy for it to be moved if need be.

Moderator Note: Thread moved, as it needed to be...

Um, are you referring to a Limited Slip Differential for a 1968 to 1975 Opel? Or something a bit newer?

[Cuz]

To be honest, I am not actually sure. A background as to why I am interested in this diff (which I have seen mentioned on these forums in numerous threads), I have a Holden Gemini (Australian) which I am in the middle of completing a turbo conversion on. The rear end is something that is somewhat of a drama - those which were supplied with the standard Gemini are largely unsupported in terms of a strong LSD unit.

There is, however, a Holden Gemini Diesel diff that came out of Japan and bolts directly into the Aus delivered Geminis whose center is fully interchangeable with the torque tube based Holden (Opel) Piazza diff. As mentioned on these forums, the Opel GT center is fully interchangeable with the Piazza center (as per the Quaife LSD available).

So, long story short, I am interested in the ZF LSD unit which is interchangeable with the Holden Piazza center (and thus my Diesel Gemini center)

[Motor Mouth]

The ZF LSD is the most reliable of the difs on offer in my opinion and much better than a Quaife one.....i run a 40% LSD in my GT.

The Holden Gemini from memory is basically a Kadett C and therefore on the German market there are numerous Difs available, be it either 40% or 75%. The good news is that the dif unit isn't just limited to the Kadett C and it can be found in the Manta A or B, so that covers 70-86 and it's also available from the Isuzu Piazza Turbo as you rightly mention.

As for the power limitations, i know the tuners of the '70's; Irmscher / Conrero / Steinmetz ran their race cars with upto about 250bhp with good reliability and even now in the UK some of the guys are running their Mantas with the 20LET engine, with these putting out 300bhp....obviously i don't know how long the dif lasts, but i think it's more likely to be drives-shaft failure rather than the dif unit itself.

If you need any more help feel free to drop me a PM, i've been known to help members sourcing the necessary bits.

[Cuz]

Thanks for the quicky reply!

Correct, the Holden Gemini has many similarities with the Opel Kadett along with the Chevy Chevelle! Unfortunately though, the Australia delivered Gemini's had a differential produced by Holden for their Torana and Commodores of the same era. The center of this diff is not interchangeable with the Piazza/Gemini Diesel diffs. But like previously mentioned I have a Gemini Diesel diff not so this is not a worry. As long as the ZF LSD fits into a Piazza torque tube diff then I will be fine!

As you mention, and based on the Quaife site, the Manta also shares the same center as the Piazza, Gemini Diesel, Opel GT and by your suggestion also the Kadett C!?

Either way I guess it does not matter where the lsd unit comes from, if it fits any one of the above then it will be perfect for my application.

Just wondering what people's experiences with the different lock %ages are? Are they only available in 40% or 75%?

It would be a godsend if you could source one of these units for me! Obviously if I could get a NOS unit I would go for that, but I would be happy to get a used one and have it rebuilt (assuming rebuild kits are available?) That way I could change the lockup % during the rebuild too?

I am planning for around 250rwkw which I believe equates to about 400bhp. Do you think this is beyond the capabilities of the LSD? Here is my plan in terms of the other rear axle components (that I posted on another forum) if you are interested:

1. Strengthed Gemini torque tube as supplied and used by CRZYFJ, Bugzy and any other reputable engineering shop willing to do the work. The principle is all the same, an alloy/chromoly tube welded over the standard Gemini one.

2. Strengthened Gemini torque tube rubber. As we know, this is a common point of failure even in standard HP Geminis. This unit has much more surface area and is made out of a stronger, denser rubber

3. Gemini Diesel housing with standard gears. This rear end has been used by a selection of Gemini drag cars with a locked (welded or spooled) center with great results, most notably Michael Sheringham's CrazyFJ which ran a sub 9 second pass. The diff housing is a straight bolt in swap (bar some small things I am yet to look at like brake lines/handbrake cable) for any Gemini Sedan/Coupe.
4. Custom billet axles. Although the Gemini Diesel axles are larger and subsequently stronger, in order to consistently take the abuse I have opted for the custom billet items

[Cuz]

I've had a few answers via PMs, but I 'm hoping to get these questions answered:

1. Just wondering what people's experiences with the different lock %ages are? Are they only available in 40% or 75%?

2. Are there rebuild kits available and could I change the lockup % during the rebuild?

3. 400bhp - Do you think this is beyond the capabilities of the LSD?

[oppositelock]

Originally Posted by Cuz I've had a few answers via PMs, but I 'm hoping to get these questions answered: 1. Just wondering what people's experiences with the different lock %ages are? Are they only available in 40% or 75%? 2. Are there rebuild kits available and could I change the lockup % during the rebuild? 3. 400bhp - Do you think this is beyond the capabilities of the LSD?

I have a ZF LSD in my Ascona B rally car and I only have experience with the 75% lockup. As far as will it hold up to 400 hp, it depends on what you are doing with it. If you are puttering around on a Sunday drive it should be fine. I suspect you intend to do more than that, otherwise what's the point of 400 hp? I wouldn't worry as much about the LSD as you will surely break the ring & pinion and/or the axle shafts before that goes. I broke the 4.75 R&P in my rally car with only about 160 hp, it's the shock loading that does it. The Ascona 400 and Manta 400 factory rally cars back in the 1980's had chronic rear axle failures with 250-275 hp. If you really have 400 hp you're gonna need a bigger rear axle. Try maybe a Toyota 8", or even Ford 9" if you are going to be doing serious drag racing or something. Lots of parts available for both of those and much cheaper than the Opel axle, too.