Hot Rods blew up two sets of zephyr gears..why?

Hey all,
Im not sure what i would like to get out of this post, as its kind of an unknown thing.. but I have a customers car back in the shop that i recently rebuilt a zephyr geared 39 gearbox for. when it first came in it was on a flatbed with no drive..the cluster and input gears both had only half the teeth left! catastrophic failure..I did find some problems with the last rebuild..and an inherent problem with the repro gearset,(they are not machined deep enough in the input gear to clear the second gear circlip, and it rubs on the inside of the driven gear just out side where the roller bearing sits) but I adressed that when I rebuilt the box.
so i ordered a new LZ gearset from Macs, when it came, it was obviously from the same manufacturer as the broken set.
Rebuilt the box, all new components where needed..felt great and changed well upon getting it going again.
maybe two hundred kilometres later, owner rings me and the box has a regular knocking sound in it. I pull the shift tower and sure enough, the front (largest) gear on the cluster is missing a tooth. everything else looks fine, apart from a little bit of marking on the input gear where the broken tooth has done a little damage.
this is behind a worked 8BA flatty,making at a guess 150-160 hp in a light 30 model coupe on A rails.
Has anyone experienced problems with the repro Zephyr gearsets? Im assuming there is only one manufacturer of these parts..pretty low volume item right?
is the cluster driven gear where you would expect failure from hard driving or clutch dumping?? The owner claims to have driven the car carefully, and I do believe him, but Im also sure I have assembled the box correctly and didnt miss any strange problems or issues with the clutch, gearbox case or other parts I didnt change.
He understandibly doesnt want to rebuild the thing again and find himself in the same situation!
I guess im interested in hearing from anyone that has had a gear failure with repro LZ gearsets, or can offer any common or uncommon reasons why a cluster shaft drive gear would blow a tooth?
thanks for any input...Ben

 

Does your customer make a habit of bump starting the car? Will tear up 2nd gear real quick if not done super gently .
Just a thought.



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if both sets of gears weren't machined great maybe the manufacturer skimped on machining and took the cheapest option, if so who knows where else they've cut corners. materials maybe?

 

4T6Ford, the car starts first crank, and has only done two hundred kays since i put the box in!I doubt its been push started at all in that time.

Fuzzybear, im always dubious of aftermarket early ford parts.. I believe these are decent quality Italian made gears, and Logic says that there would only be one producer of these parts (relatively tiny market for a high cost precision part), the other evidence to this end is that all the resellers of early ford parts list the Zephyr gearsets for almost identical sell price.
..so If anyone else has had similar problems at least I could get an inkling of the root of the problem. would 160 hp be enough to blow them up??

 

My gear breaking experience was half decade ago when I serially broke Ford script gears in an overdrive case. At that time typically it was first gear involving the cluster from flywheel assisted takeoffs. Only variation was going over railroad tracks airborne in second and finding the ground at high RPM. That landing also took out the rear gear. This unscientific sampling only shows that the gearset is not robust in the face of slamming torque pulses. I installed one of the new clusters in a late "78" case. Due to endplay issues, I slipped in one of the surviving Ford/Lincoln second and main gear. This transmission is still waiting to be tested. With the popularity of the T5 transmissions the price on Zephyr gears is much more reasonable. There may be a good supply of genuine second and main gears to perhaps isolate the problem. Good Luck: Fred A

 

Read about a similar problem here - http://www.jalopyjournal.com/forum/showthread.php?t=783128&page=11
squire ...

 

Not my car but a friend had a Model A hot Rod with a healthy 160 HP 8BA and Zephyr gears behind it .He drove the living hell out of it , goning sideways around corners and he really had a hard time keeping this trans together. He used to change gears literally on a bi-weekly basis. He switched to a T56 after he broke the Ford gear box housing. These trannys are not famous for being stout and can´t take a lot of torque and abuse. If bad repalcement gear quality comes into play aswell, it´s no surprise things will break.

 

Ford and Zephyr gears were NEVER known for strength like Cad/Lasalle. In todays world unless these gears are original Ford MO Co. I would suspect inferior materials or improper
machining/hardening.

 

Hmmm. so the feeling im getting is the aftermarket gears arent up to it..
The owner is considering going to a 5 speed..but its a lot of work and money on a torque tube car..
-bellhousing adapter
-5 speed box
-chassis mounts for box
-custom driveshaft
-banjo open drive conversion
-rear radius rods and chassis work for front mounts..
it all adds up..

I think I'll send Mac van Pelt an email and ask his opinion on the aftermarket Zephyr gears..

 

check on torque tube adapter for t5 trans, your problem sounds like the heat treating is too hard

 

Being you know what your doing and took a lot of steps to insure things were as perfect as possible and let's assume the new gear set are of fair quality is it possible a small piece of the previous blown gears found a way to hide (some times they get magnatised) and then catch a ride up between the new gears? I actually had this happen to me on a latter model 4 speed. It also was the same large front cluster gear on my box that went. It's also the lowest in the gear oil and the lowest point of the gear box. That lent it to let the Chip get into a place where it could get picked up ant that was the end of my Cluster. In my case it took some hard looking to find it. It didn't match any of the chipped gear and was magnetic unlike the broken tooth that was mostly still in tact. It was the damndest thing.
The Wizzard

 

Ford dragster transmissions by the 1960's were being re-heat treated for softer gears to absorb impact better...just like more recent soft gearsets for drag 9" rears. On stock gears this would not be necessary, but maybe the repros are glass hard...which I would consider not worth messing with. Proper original gears on a light street car should not need any consideration of that stuff.
There is an extra source of high impact loads from any end play in cluster, since endplay is taken up completely and instantly when spiral gears engage.
BUT it does not sound like this trans has anything special or violent going on, perhaps suggesting that the repro gears are crap...?
Since real Zephyrs are hard to find and expensive...why not give this thing a test period with a 28 tooth original Ford set? If that lives you will have a diagnosis on the repro Zephyrs...if those blow up in two weeks, either driver is a dangerous lunatic or there is something really odd happening in there. Sounds like all troubles are on cluster so we do not have to worry about center dimensions on upper shaft.
Assuming a normal rear ratio, 28's would likely be better, but point here is to see if real gears survive in there.

 

Thanks guys.. Bruce I was thinking the same thing.. Get a really nice 40-48 box to harvest, and put a fully matched ford gearset in it, if that breaks.. Well .. "I can't help you son.."
A small but telling part of the story.. I took the owner for a drive in another 3 speed car I built, and he said " gee you change gears really slow and careful don't you?"and I had to explain why..


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Oh, pistnbroke.. I can absolutely gaurantee the case was spotless before assembly.. It was full of busted gear shards, so I was really thourough with it.


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good luck with it....

 

Hmmmmmm???

 

Well it sounds funny right
What's the common denominator here & more probable?
Two rebuilders & both of them fucked up ?
Two sets of gears and both of them are fucked up ?
One car with a hidden issue that eats transmissions ?
A owner who thinks that you shift too slow ?

 

I'd use wet method fluorescent maganflux to check the ( new or used) gears for cracks. Dye penetrant ( SpotCheck, etc) is not sensitive enough. Sometimes finish grinding creates "heat checks" ( Cracks!!) in parts. A gear tooth with the tiniest of cracks in the wrong direction and the wrong place (near the tooth root) is doomed. Of course a used gear can be developing cracks 'as we speak" with repeated load cycles.

A harley pro stocker of the 1970s was shucking teeth off his sportster trans gears. Magnafluxing the new gears he was getting as part of his sponsorship, Deburring the gear teeth roots and shot peening reduced the cracking to the point routine magnafluxing would easily catch it.
http://i634.photobucket.com/albums/uu65/fastlane_02/SHOPPHOTOSFROMTHE90S301.jpg

 

I put a gennie 25 tooth box together in 65 behind a pretty warm 296 flattie in a 1900 LB car. Had fairly sticky tire for the time. My usual street race take off was 2000RPM and dump the clutch,never really had a problem with the 28 tooth stuff. Anyway first night out wanted to see how it came out of the hole ,so 2500 and dump the clutch. BANG!!! clank etc. Blew the entire bottom out of the case,back at the trans shop the next day . Please build me another one!! Those Lincoln gears are rather fine teeth ,short not very tall . I think under high loading things flex enought the the teeth climb partialy out of mesh then bang. Did the same shit to several sets of close ratio Vette 3 speed gears ,think the same prob ,flex in the bearing,shafts etc.

 

How are the bearing holes in the gearbox it's self. I had a 39 boxthat had a hairline crack in the rear and the holes were ovaled out. I didn't realize this and kept putting gears in it every time I blew a set up. Finally after the third set of matched 41-48 gears I put It in first, took the shifter top off and drove the car around and realized the bearings were allowing the gears to walk around and not fully engage. A new box solved this. I have not heard anything good about repro Lz gears. They are a hard trans to keep together even with good of ford parts In good shape behind a 100 horse flatty if you get on em to hard.


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Pilot error ????

 

aftermarket gear are no good try to get the real deal cheapest way is original 28 tooth same as standar ford transmission other option is to get a good used set of 25-26 tooth cluster good luck

 

X 2 the new rebop gear sets are crap, I knew it when I was putting my gearbox togeather just did not want to believe it, original Ford gears is the only way to go.

 

I think you have your answer right there.

 

Think that could be one of the factors right there....

The quality of the repro stuff makes you wonder though. The synchro rings I put in mine late last year were made in India. So far so good, but I've been relatively gentle on the changes.

 

Broken gearboxes were very common in hot rodding in the old days. It was real easy and cheap to get another one at the junk yard.



Ago

 

Operator error.

 

Lowsquire , this may be an alternative to consider ? ...
http://www.jalopyjournal.com/forum/showthread.php?t=763755

You would still need to mount radius rods and it still requires a bellhousing adapter but no more breakages .



.

 

I was thinking the same. Boxes have been known to warp and distort, especially if there was a previous blowout.

 

Any follow up on this did you ask Mac Van Pelt about after market gears ???