Repairing/Polishing Differential Ring Gear

Oooooooooh man I feel your pain, really I do. Man that is nasty and the race cracked. I thought I was the only one who had a cracked bearing race. Shoot yours completely busted in half, mine only semi-cracked.

I hate to tell you this but, you're gonna have to get a new one, or new used if you can, and they are not cheap. They only sell these things in a set. Before you order stuff, take it from me, go through EVERYTHING and then order what you need. Other wise you'll be half way through the project and find out that you need to order something else, and that will only prolong the time it takes for you to get back on the road.

If you can find used then that's the way to go, but if you can't then Dan is the man with the master plan http://www.ricambiamerica.com/. All in all, you're looking at a few grand before things are all done.

 

As for the polishing you could try these guys. http://www.procryo.com/index.html

I called them up when I first started the rebuild on my box. They had some pretty good prices, and the turn around time was a couple of days. I would send them a pic of the ring gear and see what they tell you. But in my opinion you'll be better off getting a used set if you can.

 

You could REM treat it and run it. The damage isn't on the drive or coast surface. If it fails, you can have one made. Gear and Machine Specialty, Memphis, TN. Glenn Sipe.

Goodness, folks, there are a lot of NLA R&P's around. I'm having one made for my wife's Siata now...

-Peter

 

Can a new ring gear be made and matched to an existing pinion? Can they be re-heat treated? I would imagine a new pinion shaft would be big $$$

Unrelated car, but not entirely. I used to own a SAAB SPG, and did a few upgrades for more power. Dont know what it had but was definetly well over 200 HP. But the gearbox was originally designed for a 100 HP engine, and well, it stripped off teeth from the ring and the pinion both. Funny this stuff always breaks at low speed, low power.

 

Your ring gear is not that bad and can be repaired. The burrs can be smoothed with a dremel and polished with a rubberized abrasive wheel on the dremel. you will never know the difference when put back together, you will not even hear any gear noise out of the ordinary.
I am totally serious, your damage is cosmetic as this ring gear is very hard and tough and you should have no reservations about a fix.

 

Ring gear looks to be repairable as stated above. The carrier will need to be replaced. The Testarossa diffs fail in the same manner. I replace them with a unit from Modena Engineering, its a fantastic unit that will out last the car. The diff bearings can be sourced from SKF or Timkin, they come with the races. The shims can be made very easily by a machine shop which I have done in the past.

Its not the side cover that fails, its the diff that comes apart and puts huge pressure on either the right or left side cover. Either way one always gives way when the diff comes apart. I have found most times its the left side that blows apart leaving the right side intact...yours is the opposite obviously.

 

"Can a new ring gear be made and matched to an existing pinion?"

Nope, always have to be done in pairs (at least the hypoid ones).

Might be able to do the helical final drive gears (308/328) one at a time, though.

Still think this one is salvagable.

 

And don't forget the bearings.

 

Hey Ernie, show us a picture of your semi-cracked race.

 

You can read all about it in this thread. http://ferrarichat.com/forum/showthread.php?t=77427

 

Drew

Did the trans make any unusual noises prior to the failure?

My BB trans seems to make a bit of noise at times when in neutral, when I press in the clutch it goes away

Also FYI a RP for a BBi didn't know they were different from BBs

http://www.ferraripartsexchange.com/Specials/512ringandpinion.htm

 

Drew,

Just playing devils advocate but I know you changed your gear oil a few months ago to Royal Purple do you think their is any coincidence if the diff exploded?

 

I think owning these cars long enough something will happen sooner or later just the laws of averages, unless you never drive them, or just baby them but what fun is that.


One of the disadvantages of such a rare car as the BB is the scarcity and expense of parts but the guys that own rare Ferraris from the 50s and 60s would love to have as many parts we have left for BBs from various sources so its relative. It would be nice to find a way to remanufacture some of these rare parts to reduce cost and down time when something happens though.


On JRVs site he mentioned the early 365BBs have a known soft ring and pinion though improved on the 512 FWIW.

Can they repair your diff and reweld it or do you need a replacement?

 

Here's a guy that makes them from scratch, just did a Daytona R&P and has made Boxer R&Ps before, the price goes down depending on how many made but it would take at least 5 to do it with a cad, he said the BBs are a pain as the gearing is a left turn vs regular, takes 10 weeks $6300

Machines them out of solid billet alloy 9310 I believe vs slightly softer OEM Ferrari alloy.

http://www.specialtygear.com/index.html

 

Per EPI,
"The alloy AISI-9310H is a high-quality, high hardenability, high-toughness, case-hardening steel. It is a very low carbon steel, containing only 0.10% (that's the meaning of the "10" in 9310), and commonly referred to as "10 points of carbon".

This alloy was specifically designed to be a case-hardening steel for use in applications which require high surface strength (achieved by case-hardening) combined with very high core toughness resulting from the low-carbon core. It is intended for use in extreme applications, where high contact stress is combined with high shock and impact loading.

In order to achieve the combination of surface hardness and depth of case required for a gear tooth or the inner race of a roller-clutch for example, a substantial amount of carbon must be added to the outer surface of the material, typically by the carburizing process.

In this process, the steel is heated to 1700°F and soaked for several hours at that temperature in an environment which is rich in carbon, followed by quenching and tempering. The carburizing process can produce a surface hardness in 9310 from 59-61 HRc (Hardness, Rockwell-C scale), and case depths as high as 0.060".

Because of the low carbon content of this steel, the as-quenched hardness (core and on-case-hardened areas) falls in the 32-38 HRc range, depending on whether the material is toward the low or high side of the allowable carbon content range.

AISI-9310H is typically used for premium-quality steel gears, frequently in the aircraft industry."

might explain the cost, however low volume is expensive no matter what. something i deal with on ferrari parts as well. youre american iron is so prolific that cost is absorbed on the high number of units, not to mention even thier falure rate is high also, keeps the market going.

 

You might try contacting someone at this link:

http://www.brgear.com/Engineering-and-Material-Warehouse.asp

 

Thanks

Just talked to him quoted $2500-$3000 for 9310 which he said is aircraft grade a little overkill, gues he didn't have the Ferrari tax as the other guy.

 

reproducing a part is easy enough with a CMM. from there it's onto CADCAM softeware and milling/machinig. shop hr rates and material costs make the bulk of your cost. heat treating is another step.

"ferrari tax" is a funny one, i never tell any supplier or outsource the parts final destination as they sudenly see $$$$ and figure they want cut. we have honest vendors and manufactures here and the, well not so honest.

here is another good source
http://www.arrowgear.com/

our rings are accutually spiral bevel gears, not easy.

 

Did you notice the two sources are located in close proximity to each other? Perhaps the $6300 source takes your order, and has the part made at the $2500-$3000 source, and then charges you over double for the privilege of doing business with him.

 

Could be but I am fairly sure the expensive guy does it in house, when I said Ferrari the price doubled and he got excited.

Both machine the parts on a lathe hand made, probably the same way ferrari did it back then, it takes at least 5 pieces from what I was told to make it economical to use CAD.