Lost all gear oil today, 1991 Testarossa

Your shims are on the way, not sure if you got the email. Should have them wednesday or thursday

 

there is no difference with the backlash if in neutral or a gear in

this would be 4/1000 mm, or you count now in inch size?

when you remove the crowngear you have no backlash

I once had a problem with the backlash when I used an other left cover. still had too much backlash but only 2/100 mm moving to the left side the crown blocked. it took me long time until I found the problem. the crown teeth touched this cover. so I had to remove some material from this cover. could it be you may have the same problem?

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jamie, can you make please again a small video with the backlash just now?
so like in post 681

 

Turbo Joe, that's very interesting the crown gear could hit the left side cover The ring gear can only.move to the left until it has NO backlash with the pinion. Once they're totally in mesh, there's no more movement to the left. I'm going to check the new cover which is for a 512M and compare it to my original unbroken Testarossa left side cover, to see what the difference may be between the mounting surface and the bearing bore bottom. My cover has a distance of 3.169 inches, or 80.492mm between the mounting surface and the bottom of the bearing bore. Jamie is shipping his new cover to me so I can check it out and compare.

 

why you not make it so as I suggested?
so use some feeler gauges and put between the crown and the diff. then you just will see where the problem is.

nevertheless the 3,5 mm shim on the left cover is for sure too thick, but it is easier to go down than otherwise

at the backlash video it shoes ( so I see it ) clearly that the backlash is about 1 tooth, so about 4-5 mm

 

So hear me out .. if you measure the right cover and use that to compare to the original spec one and the diff case is exactly the same .. would you just put all the same size shims on the right side as you originally had and since you don't know the exact one in the left ..just adjust with different size ones until you get preload correct ..wouldn't everything line up ..even if left plate is different ?

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Got it thanks ..I did not know probably missed that the factory diff and Neumann's diff weren't exactly the same .. cause then even with side being different that would only be testing preload which you have done

Thanks

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Flash32 if Jamie had the means to compare his old and Newmans new housing, mathematically he could have calculated what shim to use on the right side, as long as the car sounded correct before the part grenaded. No whine under acceleration or deceleration, as the contact changes between the leading and lagging edges of his gearset. I'm curious how much manufacturing tolerance Ferrari has in these parts, and think it will be a valuable bit of information.

Every part that's manufactured has a tolerance. Newman may say his parts are all the same, but frankly unless whoever is grinding the parts is almost godlike, there's going to be a difference. There are four different surfaces in just the replacement parts that can vary in length. Some maybe short, some may be long. They're only perfect if someone is taking the time to measure and verify. The overall dimension from where the ring gear seats, to where the taper roller bearing seats, is the one that counts. It changes, shims need to change. But Newman has reversed engineered his part. He probably DOES NOT have the original print that would have what the factory wanted that dimension to be. So maybe he's measured FIVE or ten or twenty of these parts and taken an average and that's HIS dimension. CNC machine tools aren't perfect, they only make accurate parts if the operator can verify by measuring. I have blueprints for hundreds of my parts, and strive to machine to print. But every part has a tolerance. Sometimes they stack up, and make a part not work right. When I look at the absolutely CRUDE looking machining in my stock differential part- holes that looked like they were drilled with a rock, holes that are WILDLY varying in dimension, I kind of think, these parts were machined FAST, but NOT with a lot of care. Automotive machining is more about speed, not quality, until someone like Newman makes them in small batches with quality in mind.

 

Thanks for the response and education .. always looking to learn.. just curious what are you using to do a precious measurement?



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A hobby homeowner can do precision measurements using any FLAT surface using a simple dial indicator that is held by a holder that is adjustable in height. In checking the Differential parts, you really don't have to come up with a length, but measuring the difference between two parts- a comparative measurement. I use Interapid .0005 dial indicators for non fussy work. A calibrated gage block set, and the knowledge of how to use it, and you can measure distances to within a tenth or two. Setting the differential gear housing on three- one, two ,three blocks supporting the part by the flange that the ring gear bolts to, and then measuring the difference ( if there is any) in heights between the taper roller bearing mounting surface. Jamie could post a picture or two, that I sent him of this happening on my granite surface plate.

I have the luxury of having MANY different means to accurately measure lengths, bore diameters and roundness. I have a Swiss made measuring machine, that it's entire range of measurement is two ten thousanths of an inch. Totally useless for this kind of work, because NOTHING in a car is machined this accurately. It has a range of measuring up to six inches, but it's comparison range is quite small. It's for checking the calibration of gage blocks. I have several measuring machines, an optical comparator, ring gages, and thread gages for every thread or bore I machine.

Surface plate work, is well within the range of the casual mechanic however. Like I said in an earlier post, you DON'T need a Starrett Inspection grade plate, a granite counter or almost ANY kitchen counter is flat enough in a six to eight inch radius to accurately measure parts. I hate even recommending a Chinese gage block set, but for this type of measurements, a hundred dollar gage block set along with a surface gage, and some seat of the pants thinking, you can measure very accurately for almost no investment. Two or three micrometers, along with gage blocks, and you're armed and dangerous.

IF everything was machined perfectly, there wouldn't NEED to be such a range of shims in these. In an ideal world these could be machined to exact dimensions. But there's TOO many places that require perfect machining to accomplish this.

 

Wow.thank you for such a great explaination

The participation, knowledge and help on this thread is truly inspiring



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those shim sizes are not only a question of the diff. also question of the gearbox and the left and right cover
and as you have written already jamie, we talk here when it comes to the end of adjustment from the thickness less than a human hair

 

One has to understand the difficulty in maintaining dimensional accuracy when machining a large part. Newmans part is small in relation to the entire transmission case. The manufacturer of that box, which I assume is Ferrari, must maintain dimensions on all sides of the case. From the bore that contains the pinion gear, in the rear of the housing for the differential, both sides need to be machined at the correct width and in relation to the pinion bore. A variance the size of a human hair, means using a different size shim. These days with CNC machines and toolpresetters, things MAY be easier. But these were made in the eighties. Think what's happened in that time with just our computers.

We may look at this one failure in these cars, but we should also think how absolutely amazing it is, all the parts that had to be machined and work together to make these cars. I'm in awe that Enzo turned his passion of racing into a car company that casts and machines all these beautiful engines and gearboxes.They MAY have a few flaws, but what a car! What eighties American car could even compare to a flat twelve engine, on top of it's complete transaxle! From the Boxers through the Testarossas, to 512 TR's, these are engineering tours de force.

 

The transmission in the TR I believe has ZF parts. Ferrari went with CNC and FMC early.

 

the inside parts are ZF, but some day F changed the manufacturer, you see this when you have gears in your hand, no ZF stamped on, but the housing I think is ferrari

 

Does anyone know where I can get the shims?

 

I think newman has, also rifledriver. and read the thread, someone once has written he can make such shims in very fast time for little money, what I myself doubt

I have at home but still stranded in thailand and so can not help. sorry