I once read that the stock ZF was good for about 550 horse power. I am not sure if that is 550 to the ground or at the flywheel. My 388 Fontana block stroker engine is making close to 600 horse power at the flywheel, and other than the typical ZF ring gear safety wire modification, I have not experienced any problems. I don't drag race my Pantera, but it has been on a road course a number of times and is driven on the street quite a bit.

Very dependent on your driving habits, 550HP may indeed be the limit for a high stress racing application, sticky tires and dropping the clutch are going to shorten the life.

and jumping whit the rear wheels off the ground whit free wheel spin and landed on the road while you are driving on the track destroy many ZF boxes.

I hope that I never jump my Pantera during a track event. The track that I use has one section that could cause that to happen, but I am not going to push the limit. I am also using street 335-35/17 rear tires, so they are not going to bite like racing slicks will. In my opinion, a Pantera is not a very good car for drag racing, so I don't waste my time with that.

I'm not sure where that rating comes from? There have been a number of monster engines installed in these cars that are considerably heftier then the rating.

In the '70s there were some 427's installed by Dennis at Pantera Performance in Colorado. A box stock 427 medium riser is an honest 450hp on a dyno (stock) but it makes 550 lb-ft of torque at 1,500 rpm.

It isn't so much the horsepower as the torque that is the danger.

According to the "factory rating" the ZF's should have self destructed under such conditions and yet they are still around?

I know in the GT40 "program" Ford was not a big believer in the ZF. They were not run behind the Mk II's and Mk IV's at all. No one seems to know specifically where that rating came form but I wouldn't be surprised if it came from  Ford back then.

They were so convinced that the ZF was a problem that they thought one out of 3 would fail in warranty use on new Panteras?

Rule of thumb though always was 500/500 is the safe limit. Venture past at your own risk. A ZF is a VERY expensive item to have to rebuild these days.

It could also be that a big number engine is what causes the swagger to current owners and they either are afraid or don't know how to use the new power? I doubt that's the answer though?

Talk to some current vintage racers. They'll know the limit.

@simon posted:

and jumping whit the rear wheels off the ground whit free wheel spin and landed on the road while you are driving on the track destroy many ZF boxes.

Les Gray has a funny story about something like this with Jim Click's GT-40...

there are a lot of exaggerated horsepower claims in the pantera community.  very few engine/chassis dyno numbers to back up claims.  add in the restrictive pantera exhaust systems, heat soaked intakes, mild street cams used, the ZF's are not being pushed while putting around to the local car show/cruise.  now if the owner is doing clutch drops and burnouts, I would think twice about that ZF no matter what the power.

Ok then is there a replacement option for the zf that is stronger? I have heard by some that the quaife ZF replacement trans is better and other that is not has good. 

Ok here is a little bit of my taught process to pick the brain of those more experienced in dooing this. In my situation my Pantera is at the project stage, with no matching engine or transaxel to think about. Should I buy a used ZF at 12000$ US and maybe having to rebuilt it a few years after or a new with Quaife at 16000Uk  if I want an engine that will give 600 to 650 Hp.

There must be parts made for the zf that upgrade thoses numbers?

Not planning of dooing any racing or drag other than the occasion event where I want to remember why I always wanted a Pantera. 

The Quaife ZFQ transaxle is dimensionally the same as the ZF and uses Porsche internals. It was developed as an alternative when the replica GT40 market took off and people were waiting 18 months to get a ZF. The problem is despite the literature, Quaife has never produced it in the upside down (to GT40) configuration required for the Pantera. There are also a number of documented failures in racing applications, so I struggle to believe it is any better then the ZF.

IMO you are better getting a ZF and should be able to obtain a documented rebuilt one for that $12K, considerably less for one with unknown history or sat in a crate for 30 years.

Julian

you can try Holinger in down under..for big $$

https://www.holinger.com.au/

and here is the headline within the forum

Direct Replacement for ZF DS-25/2 by Holinger

Thanks Matg for the link. I will take a look at this for sure

Hey Joules, 

Iwould love to beleve that you could still get a ZF for 12k all rebuilt, but in the last year maybe 2, (as with the one you are refering to 30 years in a garage) they are asking well over 10k and you are taking a big gamble that it was preserved as it says he did. 

Thanks for the post

the problem is the ring and pinion and the pinion bearing. Old style original parts are hardend to deep and will break. Also a weak point is the housing .

I did a few zf´s in the past for the M1 procars.  They normaly changed ring and pinion after 6 to 8 races . Right now we have some cars they have more than 12 races and the new ring and pinion is ok.  

fact is : those cars have 600 to 800 hp and the zf will support this after modification , but the most important thing is to set all the tollerances in the right way.

One point is realy crazy : those zf´s are 40 years old and a good one costs 10 - 15 k ! 

But nobody thinks about a gearbox service !  When you change the clutch , or replace the engine, please look at your gearbox !!

Often the bearing from the pinion is damaged or the shoulder bearings are not ok.  This cause a dramatic gearbox foult.

Here in Austria a gearbox inspection is about 1200 euro new bearings and gasket set you get for an other 800 euro , so total 2000 euro . Maybe 2500-3000 with parts like sychron rings.

(Also new ! We can fix the sychronmechanismen, when the part on the gear is damaged)

Remember : 40 Years ore more  old Gearbox !  

This maybe only 1200 inspection saves you from a total crash!

I rebuild zfs with broken ring an pinions.  When you are lucky a repair like this is 5000 euro or more !

And one point more :

Give your ZF to someone who is professional.  Do not open it by your self , do not try to "repair" it. 

Professional car mechanics do it better, thrust me.

When I look at me : I start 1995 as a car mechanic, and yes I tried some crazy fixes , but sometimes they didn t work . So my company quaranteed for my work, and I get a chance to learn from my mistakes.

Today I work for the Scuderia Ferrari and do only those cars, wich nobody can do.

My Job is based on my experience with special cars and special parts for more than 25years in this bussines. I worked for ZF , I worked for Ford and since a few years for the Scuderia. 

But when I remember my first gearbox, I remember I was in trouble with it.

When I remeber my first differential , I was in trouble !

So please give your ZF to somebody wich have experience with it. Do your job , I do my job.  I am no banker, no baker, ec  I am specialiced in cars , in motors , in gearboxes since 1995 .

Thanks

Peter

PS : If somebody is interessed here in Europe : I have a new Quaife and a new original  ZF with a stronger housing on stock.  Thanks Peter

pps : I have also the right Quaife for a pantera.  Its right : normaly Quaife do it only for GT40 mounted upsidedown. So when you turnarround the gearbox and mount it in your Pantera , you have the fastest rear dirving Pantera worldwide :-)

Change direction from the quife is impossible, because pinion is out of the middle.

So we redesigned the ring and pinion together with quaife and have the one and only Quaife Transaxle for the Pantera !  AND : The Quaife is stronger than the ZF BUT not original .  It depends on what you want.

Thanks

Peter

Just to keep you guys on the loop, Matg was correct with the fact that Holiger had a upgraded zf replacement for the Pantera that can definitly support high HP and torque (up to around 800-900). The wait period was not too bad around 3 months. He was also correct about the heafty price tag, around 30000$. There is a cool option for a paddle shift updrade at 2k. 

Even at 30k it is a temting option........

Holinger had a quick answer for me, so they seem to have a good client services... ( hope this last comment would help me nogociate a few k of this initial quote if I go with this lol)

Thx for all the great comment and help

First, the Pantera is NOT a racer. It is a Grand Touring street machine. IMHO, unless you are racing for money, swapping the ZF for anything else will be very costly. First, the frame rails which mount the engine & transaxle are quite narrow and also mount the rear suspension a-arms. So with something like a Ricardo 6-speed transaxle (Ford GT), the case is so wide you'll need to spread the rear frame rails apart for clearance. Now the gearbox fits but you've changed all of Dallara's carefully designed rear suspension geometry.

After that's somehow straightened out so the car handles at least as good as it did as-stock, getting the shifter stick in the cabin to work the gearbox reliably may be a challenge. The ZF 5-speed in other than a pro-racing venue, is known to reliably handle at least 750 bhp and in one example- 900 hp for 90 mile SS races. As long as one does not shift like an animal....  Beyond about 550 bhp, you will likely need a whole different car. And a deep-pocket sponsor.