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Lost all gear oil today, 1991 Testarossa

Discussion in 'Boxers/TR/M' started by PA32Pilot, May 9, 2020.

  1. PA32Pilot

    PA32Pilot Formula Junior
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    This is the part that will challenge me. Just so I understand correctly.

    Left side: there is a shim under the racer that helps adjust preload.

    Right side: the shim is on the side cover, looks like a metal gasket. This also adjust preload.

    I assume I will be assembling and reassembling the gearbox a few times to check and adjust preload.

    Once preload is fine I then will adjust the backlash?

    Once I do the first assembly will I know the exact shims I need or will it be trial and error?
     
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  2. turbo-joe

    turbo-joe F1 Veteran

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    yes

    no gasket, only a shim. and yes

    yes

    also yes

    don´t understand now right what you mean. but when you start you not know what you need. so best would be left side use the thickest shim you have. and right side use nothing. the diff may not have the crown on. then left side put the cover on and try to tight the right side cover. see that all around is the same distance. use 4 equal metal sheets ( so same thickness ) in 2, 5, 8 and 11 and turn the nuts handsome. during this you always check the preload. and so you may go on until the preload is ok. if less preload use thinner metal sheets, if too tight use thicker sheets. when the preload is ok you meassure the metal sheets and put one big 8 hole shim under the cover. put all together again and check the preload again. if ok then go on:

    put on the diff the crown tighten with 4 screws and again put all together to see the backlash.
    you know now the exact sizes of both side shims. so when you need right side a thinner shim you need same time then on the left side a shim exact the size thinner like the right side to have always the same preload.

    to make it easier and not always have to remove the covers and the shims for adjusting the backlash - always have to warm the left cover to get the bearing out to change the shim - it would be good to start with the left shim as thick as you have as I mentioned before. then you are sure that the "play" between the pinion and the crown is too much. fasten the crown only with 4 screws. enough when you then see that you have to go more to the pinion gear then you may loosen the screws and put between the crown and the diff 4 equal metal sheets, tighten the 4 screws again and test. this you may do so long until your backlash is ok. then you know how much the diff has to go more to the left side. so exact this size the left and the right shim has to be thinner.

    I do this only with 2 screws but then mostly have to use 0,05 mm thinner or thicker shims. so may be with 4 srews you may get a better result

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  3. PA32Pilot

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    My head just exploded lol.

    I’m gonna read this a few times. I already made my first mistake, attached the crown already. Gotta remove it and get new bolts.
     
  4. versamil

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    Setting up a ring and pinion gear may at first seem to be a daunting task. BUT, you only have to adjust two different parameters, not four.
    We ASSUME that when this box was originally assembled, using the factory measuring tools, that the pinion depth, and the taper roller bearings that locate the pinion gear, were correctly adjusted. The holes through your gearbox housing are already taken into account for your pinion depth, as you are ONLY replacing the housing. So you have the bearing preload to adjust, and then really JUST the backlash on the ring and pinion. You are NOT setting up the entire meshing of the ring and pinion. The bearing preload is determined by the distance between the side covers and the bearing cups. They are using the shim behind the bearing cup in the ruined cover, as the main preload adjustment. NOT very simple to adjust if you have to heat up the cover and knock out the cup every time. IF your original bearing cup is not destroyed, from the housing grenading, this cup can have about a thousanths ground off the OD. NOW you have the ability to change shims, without heating up the side cover and banging out the race.

    Grinding this race round and concentric can be done on a cylindrical grinder. You're only removing enough material to make it a sliding fit, instead of a press fit. Even using a belt sander with a 80 grit belt, you could probably roll the bearing race around by hand enough to remove a small amount of material.If it slides into your side cover with no effort, you've just made your life easier. This is assuming the NEW race is machined to the same dimensions as the old race. I hate to say it, but the tolerances on taper roller bearings are NOT as precise as you would think. The distance between the back side of the cup, and the actual bearing surface is NOT held to exacting dimensions. IF your original cup was badly nicked and damaged, just buy TWO cups and grind one. In the scheme of things the cup is CHEAP, at a bearing house.

    If the Newman housing was machined to exactly the same heights as your original, you wouldn't have to change anything. BUT the critical dimension, the distance from the flat face where the removable side cover bolts on, to the back surface where the taper roller bearing abuts, at the left side cover, has been lost. So you can't adjust the bearing preload using original parts. The BACKLASH, that's set up with the large shim on the passenger side cover, may be accurately gaged however. The distance from the surface your ring gear mounts to on your new Newman diff housing, to the flat bearing surface that the taper roller bearing presses against on the removable cover, is an important dimension. If you retrieve your new flower pot holder, bolt your original cover back onto it, and measure the distance between where the back side of the taper roller bearing abuts, to the ring gear surface, this is an important dimension. Then you need to compare what this dimension is with your NEW housing, The difference in these two dimensions will be the distance your spacer ring on the passenger side cover needs to be adjusted for. This is SO simple to measure with dial indicators and a surface plate or actually your granite counters in your kitchen. Since your original housing is destroyed on one side, you'll have to hold it up parallel using spacers under the ring gear flange. Using the same spacers under the new housing to measure with, lets you just do an A-B comparison. Of course you need to measure the thickness of the flange on both housing to see if they are exactly the same. A zero to one inch micrometer, or for less accuracy, a dial caliper, and you're off to the races.

    You can call me if you need more info. I feel it's WAY easier to do critical measuring of parts, on a surface plate, (or your kitchens granite counter), rather than crawling under a car, and being crude. Precise work is simple to do, with just a few basic measuring tools. If the ONLY variable you need to adjust for is bearing preload, replacing shims in the drivers side cover, you're NOT going to be hating life. I have built over two hundred spiral bevel gear gearboxes, where I have to set all four variables, so I kind of have this pretty well figured out. The Testarossa differential, has half the job already done.
     
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  5. versamil

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    In my last post I did mention bearing tolerances on taper roller bearings. IF you're using two different races to set up your back lash, the one ground race for quick disassembly, re assembly, and then your NEW bearing set- you can check to make sure they are the same dimensions, by checking the assembled height of just the race ( the CUP) and the CONE, ( the part of the bearing with the rollers), by putting them together, side by side on your surface plate, and just checking that the assembled heights are the same, using a dial indicator, and height gage. Two essential tools for anyone doing this kind of work. A set of GAGE BLOCKS, and a person can really do some accurate work with very little invested.

    I bore cast iron housings for bearings on Swiss boring machines. I'm able to control my bore sizes to within a few tenths. I was shocked to find, that taper roller bearing races were within tolerance with a thousanths and a half variance in OD dimensions. So if I bored a housing using a race as a guide for my bore size, I actually have to check ALL of my races to see where they're at in size. A variance of .0015" is the difference between a press fit and a sliding fit. In machine tools, a thou and a half is a MILE !

    The reason I mention this, is you can't ASSUME anything about bearings. Having the ability to measure accurately is everything.
     
  6. PA32Pilot

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    First, thank you for taking the time to write up such an informative post.

    Second, a FChat member shipped me a machined race for the drivers side. To be honest I want sure what this but now I understand.

    My race on that side was destroyed so I can’t use it but it was Timkin 362A.


    The race I was mailed is also 362A. So I’m assuming I owe this FChat member dinner as he did me a GIGANTIC favor and saved me some work.
     
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  7. PA32Pilot

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    #582 PA32Pilot, May 23, 2020 at 4:22 PM
    Last edited: May 23, 2020 at 4:30 PM
    I am going to do this, but I made a mistake and already attached the gears to the new housing and torqued them down with loc-tite. I am going to have to remove the gear.


    Should I take this measurement with the old bearing and race or wait for the new ones?
     
  8. PA32Pilot

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    Also I am looking but maybe I am looking for the wrong thing. I cannot find the shims for the drivers side race.
     
  9. PA32Pilot

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    Ignore this. I am going to press on old bearing to of housing. Then press new bearing onto new housing.

    I can then take measurements from new casing. Then I’ll swap gears and take measurement from old. Then reassemble new casing with gears.
     
  10. Newman

    Newman F1 World Champ
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    Dont shim under the gear. 365 boxer has one there and I can only assume it had to do with the continuing ratio changes and the std shim range would not apply if they didn't relocate the crown gear to get back into that range.

    Take the existing shims and install them with the new diff and no crown gear. See how it spins. If there is drag, a nice smooth resistance bearing in mind it will loosen up once used then take it apart and put the crown gear on. If you have to squint and close one eye to be able to turn it, its too tight. If it spins like a roulette wheel its too loose.

    Check backlash after you have that preload / drag correct.
     
  11. Newman

    Newman F1 World Champ
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    Now in your situation you have two variables, most have one. You have a new side cover and a diff, tolerance stack-up can help you or hurt you.

    If preload is good and backlash is off you have to add or subtract the same amount from each shim to move the diff left or right. To move it right you add to both, subtract from both to move it left. Maintaining the same amount means preload is unchanged regardless of how far you move it left or right.
     
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  12. PA32Pilot

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    So your saying don’t shim the crown gear? When I removed it there was no shims under there.
     
  13. PA32Pilot

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  14. Newman

    Newman F1 World Champ
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    If preload is tight loosen the right side support until it feels good and slide a feeler gauge in between the cover and shim to determine the new right side shim for the time being but you dont need a shim yet. This is where it gets hard to explain but not hard to do. If you know you need to set a .003" gap on the right side then put the crown gear on and set that right side cover to .003" again using feelers and check backlash. Now you'll know what your next move is. You may need to eliminate that .003" gap on the right and deduct .003" from the shim under the cup to get back lash right....or not. You made need to add .010" to each. You wont know until you get there.
     
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  15. Newman

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    Correct, dont shim under the gear. I saw Romano's post showing a shim under the gear but didnt read the post entirely, just not wanting to confuse the matter.
     
  16. Newman

    Newman F1 World Champ
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    Yes thats the shim. Yours was in the pile of debris, might've been broken I dont remember. Its a ground ring about 1/8" thick.
     
  17. PA32Pilot

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  18. PA32Pilot

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    Ok so for preload I am going to:

    Install differential, both side plates and both axle flange.

    Turn to test resistance, shouldn’t have to squint to turn axle flange.

    Once this is ok I will remove all parts, install crown gear. Now test backlash.
     
  19. versamil

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    This question is really more for Newman. Since you manufacture these parts, and obviously reverse engineered a stock part to get to the dimensions of your completely machined housing, have you found that the stock housings varied very much? There's quite a few different machining operations to build the entire gearbox, that any depth that's machined too deep or not deep enough, means shims need to be used. BUT if the housing you build is made accurately for the distance between the one side where the bearing race for the taper roller bearing is ground, and the FACE kissed with the side of the grinding wheel, and is the SAME distance as an original part, ALL the stock shims could be reused, as long as the part didn't explode, like Jamies. BUT Jamies car has an unscathed passenger side cover, and race, with the stock shim between the cover and the gear box. Shamile DROVE this car for tens of thousands of miles, and obviously didn't hear any noises. The original shim worked for the dimensions of the parts. The ONLY thing that can change with the gear housing being changed, is the distance between the ring gear mount and the bearing mount. If this dimension is HELD, there's no need to be concerned about the backlash of the ring gear, and the only variable will be the bearing preload. Jamie obviously will need to figure out the shim to place behind the bearing race on the drivers side, but that's it! IF he had an oversize shim in thickness behind the cup, install the gear housing into the box, install the right side cover with stock shim, and then install the drivers side cover until the bearings seat. The cover will protrude from the housing the amount that the oversize shim is too big. But then the bearings need some preload, so a certain amount extra needs to be subtracted, to get the bearings loaded.

    Without the ring gear installed, using the original large shim on the right side, with the cover installed and tightened, the bearing preload should be set. If Newmans part accurately follows the original, and the original parts are made to SOME sort of quality standard for dimensions, bearing preload should be his only concern.

    Anyone replacing their housings before the part fails, MAY be able to just reuse ALL of their original shims and be fine. I'm going to accurately measure my first part, and then compare it to my second Testarossa, when I get to this project. It WILL be interesting to see if the dimensions vary between parts. the more parts that can be measured to compare, the more accurately we can conclude that they WERE made to some sort of quality standard. If there is a difference, between several stock parts, then the replacement housing COULD have one dimension that could be ground to fit. This is everyday work for someone who grinds machine tool spindles. I grind the shoulders where a bearing abuts, and a shoulder for where the gear presses against, measure the distance, and then grind to the correct dimension.
     
  20. PA32Pilot

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    Very good read, a lot of smart people on this board.
     
  21. PA32Pilot

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    Question I’ve been meaning to ask. In all my time working on cars there are always gaskets.... the Ferrari has NO gaskets!

    There is this white silicone glopped into some bolt holes and there is a thin layer between some covers.

    What silicone is this?
     
  22. versamil

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    So I just checked my parts just to get a figure and make sure I wasn't spewing out a bunch of crap. If you want to ELIMINATE any worries of the backlash, this is EASILY measured on a surface plate, your granite kitchen counter top, OR take it to a machine shop. I used three 1-2 -3 blocks to hold the differential gear housing up off my surface plate. These blocks support the part by having the ring gear mounting surface resting on them. This gives the bearing mount for the drivers side, room to clear the table. If you zero your dial indicator on the top of one of the three inch tall blocks, this is the zero reference for where your ring gear is mounted.Then raise your dial indicator and have it zero again resting on the surface where the taper roller bearing abuts. On MY part, this dimension is 2.694 inches. That doesn't mean ALL of them are this, but they should be close. You aren't working to a dimension however, you're doing a comparative measurement.
    You want to determine if both your new part and your old part are the same, and if they are not, you have to figure out what the difference is. Other than installing a new taper roller bearing and race on the passenger side, you have done NOTHING to change the backlash, other than change the housing. If this measurement isn't the same, then you have to either get a thicker or thinner housing shim. I'm not sure if Newman provides a new plate that the passenger side bearing is pressed on, or whether you reuse the original. These measurements are done without the bearings installed. If you're using the original bolt on plate, you could also check without it bolted to the new housing. Just compare the dimensions from the top of the one, two, three block, to the machined flange of the housing, where the plate bolts on that tensions the clutch packs. Check both parts with the same set up. If this dimension is the same, you're golden.

    Measuring on a surface plate, is way easier and less frustrating than fiddle farting around under a car. It's also a precise way to determine things. Can't imagine jockeying around all this stuff under a car, when you can do it so easily with relatively simple measuring tools. To come up with an actual dimension, and not just a comparison,a serious hobby homeowner could buy a cheap set of Chinese gage blocks. I can cheat by just using the measuring equipment on one of my SIP boring machines, but at 38,000 pounds, most people don't have one in their garage.

    I have rebuilt well over a hundred engines, and I used to use Porsche case sealant for metal to metal seals. It was made by locktite but it was ONLY available from Porsche dealers. I think Hylomar is another sealant for the same application. The sealant from Porsche had a name in German, pronounced FLOCK N Dick Ton.
    I bet Turbo Joe knows! I think it was Locktite 574. I stopped doing cars in 1999, and back then a tube was fifty bucks. I wouldn't hesitate to use another sealant made by Honda, I think it was called Hondabond. In a period of ten years , I rebuilt at least forty Maserati Bi-Turbo engines, and NEVER had a leak with the Porsche product, so I'm definitely a believer. I'm NOT a fan of normal silicone sealant. The quality varies, AND it has a shelf life. There's better sealants than plain old silicone. For silicone to seal, your parts MUST be perfectly clean. When using it, I TRY and not touch the metal surface I'm sealing. I clean my parts just before assembly with lacquer thinner, and then carefully assemble. It's WAY easier to be meticulous in assembly and try and put all the balls in your court, than have to dismantle and clean up a machine because there is a leak.
     
  23. turbo-joe

    turbo-joe F1 Veteran

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    those "shims" ( feeler gage plates ) I only use to know how much the diff with the crown has to go to the left without always removing both side covers and to know then the exact size how much the diff has to go to the left.
    please read my post completly paul, then you also can see how easy all this adjustment is.

    as brain has written, only 2 adjustments are needed and not 4 as if you rebuilt the complete gearbox.
     
  24. Newman

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    The factory units are inconsistent, the ones I supply are not. The other variable that has to be taken into account is if the diff was set up correctly in the first place either at ferrari or the last tech that rebuilt the box. Those factors will decide if you use the same shims or not. I've run into situations where the backlash is correct but the pattern isn't ideal because the pinion depth is wrong - I like everything to be perfect but in the real world you have to make a decision. The car was running and driving down the road with a less than ideal pattern and its here for an upgrade. Should I change that pinion setting? Its a used gear set that's seen some miles and some wear. Do I change the pinion depth and introduce a gear noise to make it "right" or leave it alone? The correct pinion shims that fit under the bearing cup insert pressed into the box aren't available which means making them or shim under the pinion bearing instead as a shortcut but the end result could be noise on tip-in.
     

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