Has anyone had the dreaded transaxle/diff failure?

Cast metal will not be strong enough. It either has to be a forging (very expensive for one piece) or made from a very high grade piece of billet steel and machined.

I suspect by either process by the time you are done you will wish you had just bought one.

 

Gentlemen, as I recall it the new differential was only a couple thousand dollars from T Rutlands if memory serves. It was no where near the $8,500 quoted earlier. I don't think this justifies re-engineering another one.

Let me look at the bill tonight and get back with what I paid for the updated differential. Remember this is without the ring and pinion.

 

The 8500 quoted earlier was a CND price, with side covers, and all other associated parts needed to complete the job.

 

Painful pics to look at. Please allow my possibly very stupid question here: could the occasional 'grinding of the gears' when shifting hastily result in such damage, accumulated or catastrophic?

 

No, totally unrelated. Launching the car hard, thrashing it or locking the wheels on downshifts will and im sure time is a factor too.

 

So how many of these have occured?

If you're a TR owner ( or considering one ) should you just budget for a replacement and do it at some point before it fails?

 

Wow, especially knowing that my TR is sitting there waiting for a new tranny, these pictures REALLY hurt.

Do the repairs EVER end???

Guess not

 

Thanks.

 

OK, I just looked at my bill from T Rutlands. "Diff. Assy, T/R Updated" lists for $3976.81 and I purchased for $3156.30 USD. So more than the couple of thousand I posted earlier. The part number is 155099 but this may be a T Rutland's part number. There were a couple of thousand of dollars more in "other parts" and with labor of around $3,000 that is consistent with the $8,500CD Hugh quoted earlier.

 

So what ever happened to your trans job? I remember something about a gear breaking or something like that. Im sure you are fixing it right now that you have gone this far and maybe you should upgrade your diff carrier while you are there.

 

Here is my differential housing ... notice the cracks... it actually came apart in my hands when I went to pick it up
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Here is the exploded view (forgive the pun, hehehe). The area of failure is behind the ring gear in the pic but the bolt on end cap at the other extreme end doesnt fail. Its like they bolted one end on and welded on the other. The upgraded unit doesnt have the welded end cap.

The pic of testabobs is of the diff carrier support, not the carrier housing. Once the end cap weld breaks the carrier wobbles like a spinning top and breaks whatever it can. Now the pinion gear meshing with the unsupported crown gear tries to push the crown and carrrier out the side of the gearbox and the teeth on both gears are almost certian to get damaged as well. Add to this the rolling mass of the car mechanically connected to the carrier keeping it in motion to do even more damage until you figure out what just happened and then pull over. If the carrier is replaced prior to failure the crown and pinion as well as the carrier supports wont get wrecked. Not to mention the transmission can remain assembled and its a quick swap/upgrade during an engine out. Its just either expensive or very expensive depending on when you do it.
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The red line shows the weld that breaks. I should have pointed that out in the first place.
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Can someone fill me in on the various points here.

It seems the diff carrier is suspect, is this seperate to the box and independantly replaceable.
What is the twil shaft, is this related to the above.

Assuming a undamged transmission, can a diff carrier and twil shaft be replaced for a reasonable sum during an EO service. Is there an aftermarket diff carrier assembly and twil shaft that is better than a 512 one that can fit a boxer.

In other words what to replace and where to get it for an undamged boxer that one wants to make "bullet proof"

 

The quill shaft transmits torque from the gearbox output to the pinion gear and is prone to break as well. The carrier also breaks but is the bigger problem and sure does a boat load of damage when it goes. I would not use another factory boxer carrier as a replacement, buy a 512TR carrier or an aftermarket unit. The 512TR unit has no welded end cap like the original boxer part which is the problem. I would pass on replacing the quill shaft and just go for the carrier upgrade. If the shaft breaks it can mess things up by spreading debris through the gearbox which is a pain to clean out but the carrier will destroy several components in an instant.

 

Who makes a good aftermarket diff carrier and what is the total cost of the whole shebang assuming the engine is already out.

 

A 951 box can handle 750 BHP....evil smile...=)

Sorry, too lazy (tonight) to read the whole thread.

 

One could have the piece CNC'd from 6061 Aluminum billett. It would be extremely strong, one piece, and most likely moderately priced. Any good machine shop should be able to do this, by copying your original.

In addition, while apart, I would recommend that all parts be magnafluxed to check for cracks. That way one knows for sure that all the internals are sound.

Before installing new parts, either steel or aluminum, be sure and have them cryo treated. It's cheap insurance, and makes them very resistant to expansion and contraction which can lead to stress cracks!

After the cryo treatment, put the parts through a low friction coating process. It's inexpensive and well worth it.

 

Think you mean 512M diff the 512TR is the same welded unit. The quill shafts came in different diameters from what I have learned, I had mine out when replacing the clutch and was suprised how it was so tapered in the center and thin, looked fragile clearly for a reason though

Funny all the pics in the Nichols book showing the 365 having extremely hard` launches lifting its front end and smoking its tires in the test mule Ferrari never experienced consistent failures of them.

 

365's had much less tire and torque than a bbi. The 512bblm seemd to suffer terribly from tranny/diff problems. More power more tire and it seems to go bango. Although a slightly modded boxer will not really have more power or tire than a testarossa, and if those lasted 85k then maybee its ok. Still if you like to drive fast its nice to know that things are as close to bullet proof as possible. Since I do not do hard launches and can double declutch downshift my diff probably has it pretty easy, but still spendin an extra 5k at EO sounds like a lot less than 20k and an unsheduled stop.

 

I have waited to repair my tranny, searching for the best solution before I embark on the costly repair, and I am very glad that I did, because I have chosen to completely replace the tranny with an F512M unit. Just put an email in to T Rutlands for a quote.

If I had read all of the recent comments, I would have just fixed my current box with a probable failure in my future.

Thanks to all for your input and experience!

 

David,

I was just thinking about your green TR and was going to PM you about what you were doing with it. You answered the question here. Good luck with it! I love the off color cars (mine included)!

Regards,

Art S.

 

Several Ferrari factory Service Bulletins cover some of what is being discussed in this thread.

SB 30-23 describes the new forged differential housing, part number 155099 that was incorporated in the 512TR somewhere around the 1994 model. It replaced the previous welded type. Checking the gearbox serial number will indicate which housing your 512TR has. The SN break is 1370 and later. Another improvement was made at SN 1513 whereas a later ring gear mated to the differential with dowel pins and bolts of finer thread than previously. My 1992 has gearbox SN 314 which is much prior to the forged differential. The SB states that the forged differential will also fit the Testarossa but does not mention the Boxer series.

SB 30-23 also announces a new, stronger bolt to attach the ring gear to the differential. It is the courser thread allowing you to retain the older ring and pinion gear and could be used with either the welded or forged differential. I had planned to install these bolts when I do an engine out early next spring, but my fear is increasing enough about the welded differential that I may replace it also.

SB 30-18 describes a new heavier propeller shaft incorporated in the 512TR commencing with engine number 31108. My engine number is 29896 so this probably occurred in 1993. The propeller shaft is what was previously pictured and referred to as the quill shaft. It transmits power to the transmission from the gearbox attached to the clutch housing. When I had the gearbox off to work on the throwout bearing this shaft slipped right out of the transmission. The female end goes in the transmission and male into the rear gearbox. The earlier shaft was 17 mm diameter while the improved shaft #151651 is 20 mm diameter. If my calculations are correct that is 38% more mass to the diameter of the shaft. The new shaft will fit the Testarossa and the 512BB according to the SB.

I think the above production improvements of the late 512TR's carried over to the 512M with the same part numbers but don't have an M parts book so cannot verify this.

I don't do burn-outs, drag race, or anything wild but do enjoy full power acceleration in 2nd and 3rd gear after the clutch is fully engaged on dry and smooth pavement. Maybe I'm being over cautious but I don't know what the previous owners did in their 19,000 miles. I've put on over 13,000 mi. with no problem, BUT, my fear increases with every drive.

Ron

 

Ron,

Thanks for the post. I will have to start digging around for serial numbers on my car.

Lloyd