ZF failure?

Russ Noble · Feb 12, 2007

The similar thread that I started for 930's brought out quite a bit of interesting information. Richards TRT thread was starting to drift into ZF capabilities. Maybe this is a better place to discuss that and help sort out weaknesses, strengths, modifications etc.

Cheers

John W · Feb 13, 2007

It wouls also be handy to know under what circumstances any failures occured.
e.g.
Big block or small block (CIs),
what sort of power/torque (maybe the cam type would be handy, to give an indication of the curve)
street, strip, or track use,
how it failed (ring, pinion, gears, casing, etc)
how it was cured.

Cheers :lurker:

llarsen · Feb 13, 2007

Class act, Russ!

Russ Noble · Feb 13, 2007

Thanks Lynn.

Whilst I started the 930 thread coz there wasn't a lot of info out there, there IS quite a bit on the ZF now that I have a quick look.

I never really considered a ZF for myself because of cost, so didn't look for any info on them at the time. Also if Ford didn't run them because they knew they wouldn't last one whole day behind a big block, that was another good reason not to use one. But there is a lot of info in this thread
http://www.gt40s.com/forum/gt40-tec...es/16311-zf-transaxle-use.html?highlight=fail

However new info of the type indicated by John W would be interesting, as would links to any other threads which cover this subject.

Cheers

RamboLambo · Feb 13, 2007

Ahh yes. The best Ive got to a ZF box is carrying one (struggling) around a workshop!
But seriously, from the photos Ive seen of the internals, the gearset is seems very small. Perhaps someone who has one in bits can measure the gear width, shaft spacing, shaft diameters and crownwheel size for us so we can add that to our database of gearbox specs!

ross nicol · Feb 18, 2007

John W
I think we should add to your list, what tyres used, road/track surface and last of all the largest variable "The Driver" (Just like these musicians I deal with who claim they were'nt playing loud and their speaker voice coils are fried) a driver normally won't own up to being brutal with the gearshift.So a survey like this is most likely doomed from the start.I will just keep on telling you guys how good mine is unless it breaks, and surely none of you will deny, racing with standing starts is the hardest test on a gearboxes strength, so pontificate as much as you like but please get real with the test criteria.By the way Rambo Lambo I can assure you the ZF weight of 60-70kg is not in the alloy casting so don't worry about the capability of the gears or the crown wheel, that's Ford 9" type size and we all know the strength of that. Actually I reckon Ford were worried like Dan Gurney that AJ Foyt would break the car and as I remember it Dan tricked him into using less revs.Of course this was at the time the Collotti disaster was happening too so the ZF may not have been proven.
Ross

John W · Feb 19, 2007

Ross, its not my list, its Russ's thread

Agreed, some people are symathetic and others aren't.
It all seems acedimic though as judging by the responses, it would appear there haven't been any failures

Russ Noble · Feb 19, 2007

John W said:
Ross, its not my list, its Russ's thread

Agreed, some people are symathetic and others aren't.
It all seems acedimic though as judging by the responses, it would appear there haven't been any failures

John, I don't know that statement is necessarily true, there are other threads here which talk about cracked cases and there are photo's of stripped gears also on this site. I don't have the time nor inclination to hunt them down.

BTW, it's not really my thread, I was just trying to move the discussion off Richards TRT thread.

Cheers

ross nicol · Feb 19, 2007

Hi John
Yes I think Russ was getting sick of his 930 thread being hi jacked which I have to admit I am guilty of doing too, and starting this one probably was the right thing to do.ZF failures do seem rare but it doesn't appear to have stopped some from claiming it has x Torque capability. This armchair type power handling shootout really gets to me because a sympathetic driver could probably double the torque input to his box and still have it survive IMHO of course.What I find in racing though, it is hard to be kind, so having the strength of the ZF is very comforting.
Ross

Russ Noble · Feb 19, 2007

Ross,

I don't think there is any question that a ZF will easily handle a 302. I'm sure it will stand any abuse you throw at it. John Wyer was obviously confident that it would do the job too! And it did!!!

It's the big cube motors that cause problems with the ZF and that is what led Ford to develop the T44.

Cheers

Paul Fleming · Feb 22, 2007

Does this constitute a ZF failure ??

Ron Earp · Feb 22, 2007

Paul, I'd certainly say so. What were the conditions of that failure and the condition of that box before failure?

Ron

ross nicol · Feb 22, 2007

It has been known for the bolts that hold the crown wheel to back out.The bolt or bolts, can harmlessly fall to the bottom of the case or can jam the C&P. In this case it seems the latter may have happened. It is recommended that anyone who owns a ZF have the bolts lockwired.
Ross

Paul Fleming · Feb 22, 2007

I believe that this was caused buy a pinnion bearing failure, the bearing seized and the whole lot just let go. There is an awful lot talked about lock wiring the crown wheel bolts, and quite rightly, but equally important is to lockwire the cap head bolts that hold the end plate on the end of the diff. on the /2 diffs. I have had boxes in where these bolts have come loose, the planet gears then force the ramps apart causing considerable damage.

jac mac · Feb 22, 2007

In the pic above the lock wiring is not correct. Rather than try to explain it in words get hold of a 'Standard Aircraft Handbook' and check out the correct procedure.

Jac Mac

John W · Feb 22, 2007

Holy crap Paul, that looks expensive !!

Jac, I'd love to hear a brief summary of why the lockwiring is not right. The chances of me finding a standard aircraft manual are pretty slim...

IanAnderson · Feb 22, 2007

John

The lock wiring should be done in such a way as it is pulling on the one bolt clockwise and going to the opposite side of the next bolt head. (also tending to pull that clockwise (or tighter if left hand thread))

In aircraft the wiring would be done in small lengths (between 2 bolts) and not daisy chained.

And to be picky there shoud be a minimum of 12 twists per inch

In effect the wiring above is only usng the strength of a single piece of wire instead of a double (twisted pair)

Have a look at the safety wiring on the boeing wiper motors - a work of art!

Ian

David Morton · Feb 22, 2007

Ian,
The 747 wiper system was not all that. I lost a complete arm and blade
from the right windshield somewhere over Burnham in the early 90's. It was never found so maybe it dropped near a gt40 owner's house. Maybe the 707 system was better (much shorter).
ps. My 2 ZF boxes are wirelocked in the manner you described - the same as JAR requirements and all that.
Dave M

Pantera1889 · Feb 22, 2007

Here you go.

jac mac · Feb 22, 2007

John W, Ian has described it correctly apart from the 'Left hand thread' bit , I am sure he meant Right Hand thread.

At the end of the day lockwire is only a safety net to prevent the bolt from dropping out into the works of whatever it is installed in. If the crownwheel bolts do come loose there should be a noticable change in drivetrain noise and it will depend on the owner /drivers common sense as to whether immediate action is taken to investigate this. While I have not had any 'hands on' experience with a ZF it would appear that the crownwheel bolts have fairly coarse thread, the 930 etc also. The Ford 9" etc use 7/16" SAE-UNF bolts and dont seem to have many problems in this area, just my observation.

Jac Mac

ZF failure?

Russ Noble

John W

Lynn Larsen

Lynn Larsen

Russ Noble

BruceA

Ross Nicol

John W

Russ Noble

Ross Nicol

Russ Noble

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Ron Earp

Ross Nicol

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Jac Mac

John W

Ian Anderson

David Morton

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