Differential Preload and turning torque measurement, possible alternate procedure? | FerrariChat

Differential Preload and turning torque measurement, possible alternate procedure?

Discussion in 'Boxers/TR/M' started by mexicruiser, Sep 19, 2020.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
    241
    Full Name:
    Jon
    Warning, the following is not intended as advise or substitute for wsm procedures, I post it because it would help me as if others chime in and check if I am not missing something in my calculations.

    I’m trying to find a way for diff carrier preload measurement without the ferrari tool and no pinion nut access, if this seems like too much science for a simple thing I apologize beforehand, I sometime do this.

    365/512BB/512BBi manual spec is 1.8-2kg for pinion preload measured with ferrari tool (pulley on pinion), and 3.6-4.0kg for pinion+carrier preload using the same tool (10-20% less for used bearings)
    In the manual the tool appears to have a 200mm diameter, there is a text referring to tool 200 0 (see attached pic) any way of confirming this?
    Engaging fourth gear (1.08:1 ratio) enables me to measure turning torque on the prop shaft by carefully fitting a 22mm 1/2” drive socket over a shop towel on the splined end (attached pic).
    3.8-4.0 kg on a 200mm diameter pulley (100mm radius) equals to 0.38-0.40kg/m which in turn is 3.7-3.9Nm reduced by the fourth gear ratio of 1.08:1 is 3.4-3.6Nm.
    Half of the 3.4-3.6Nm turning torque is for the pinion so 1.7-1.8Nm for the carrier (measured thru the pinion reduction), minus 20% for the used bearings equals 1.36-1.44Nm carrier turning torque, 1.4Nm to simplify things.
    Now, the manual has the same spec for all end gear ratios, but there is a disclaimer stating it the original manual for the 365 and is not completely updated for other models, so I will have to asume this spec is for the 365GTB4 3.75:1 ratio, so this would translate to a 6.5Nm (new bearings) or 5.25Nm (used bearings) measured at the diff output flange nut.
    If I want to measure the total turning torque thru the prop shaft I have to reduce that spec with the installed gear ratio (3.21:1 on my BBi) and add the current pinion turning torque:
    If I remove my diff and I measure the pinion turning torque I get a very low 0.6Nm reading.
    The 5.25Nm (used bearing carrier turning torque) divided by 3.21:1 gear ratio is 1.64Nm.
    Finally this means I should have 2.2Nm (0.6+1.64)total turning torque measured at the prop shaft, if the carrier preload is set up correctly with my used bearings.
    —Things I’m still not sure about but are probably an issue:
    A)Is the 10-20% less preload meant to test the used bearings as installed accounting for wear BEFORE removing the diff, not after reinstalling it? This would mean that for reinstallation you should strive to achieve the new bearing spec?
    B)Is the size of the ferrari pulley really 200mm or is the info on the manual (200 0) the tool id number?


    Image Unavailable, Please Login Image Unavailable, Please Login
     
  2. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,868
    southwest germany and thailand
    Full Name:
    romano schwabel
    what is this blue shaft for?

    sorry, I not understand this now. the prop shaft has nothing to do with the preload from the CP bearings. if the gearbox is in neutral and you turn the prop shaft the CP is not turning. only when you put in a gear, and then this 2.2 Nm depends on what gear you have in.

    when you like to check the preload from the diff bearing exactly then you may remove the crown from the diff

    and when you like to check the preload from the lay shaft then you turn this shaft in the front of the gearbox without the diff inside, of course when the gerbox is in neutral
     
  3. c4b4the04

    c4b4the04 Formula Junior
    Silver Subscribed

    Jun 9, 2017
    383
    Northern Virginia
    Full Name:
    Cassidy
    My understanding from the manual (Testarossa) was that you install the axle flange (no axle output seal) and mount the torque tool to one of the CV bolts. It needs to be in a range as you stated.

    Quite honestly when we set up my carrier, we used new bearings and we got a good pattern on the CP gears. The diff is 'stiff' to the turn, similarly to any Dana or other diff you may have done. I personally wouldn't trust anything measuring through the gearbox as you've got too many variables there. If your pattern is good and you used a slip-fit race to adjust preload with the shims, you will be close on preload. Maybe Newman can pipe up here, lots of more experienced folks than me have set these up. Mine is 800 miles on and doing great so I likely got it right.

    Cassidy
     
    mexicruiser likes this.
  4. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
    241
    Full Name:
    Jon
    It would be great if someone could confirm the diameter of the ferrari preload tool or if anybody who is better at math than me would check if I am missing something.

    Interesting! Does anyone here have the Testarossa wsm? What are the instructions there?

    I can check turning torque for the diff directly at the flange bolt, but if my calculations are correct and the ferrari tool size is correct I arrive at requiring around 6Nm, which translates into more than 10kg with the string around the diff and pull method and definitely very hard to turn by hand at the flange. This bothers me because everybody else here seems to be putting very little preload on their diffs. I would hate it if break a gear set (Which can happen if the diff preload is low) especially after what is supposed to be an upgrade to avoid diff failure.
     
  5. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
    241
    Full Name:
    Jon
    The blue shaft is there to fit the dial gauge to measure backlash,

    I know the prop shaft normally doesn’t have anything to do here, but I don’t have the ferrari tool so disassembling the transmission to gain access to the pinion is useless.

    I was trying to Mathematically determine what the ferrari wsm preload spec would translate to if measured on the diff flange (no crown gear) or by the prop shaft (crown gear installed)

    I’m concern that the common methods posted elsewhere here could be applying too little preload.

    When I removed my diff there was a 0.5mm gap on the side covers for preload, if I apply the same preload to my new diff it is very hard to turn by hand and needs 7-8kg pull on the string to keep it turning.
     
  6. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,868
    southwest germany and thailand
    Full Name:
    romano schwabel
    this is too much

    also too much

    do a search, the new owner of shamiles car did all the diff by himself with the help from this forum here and he took some short videos and posted here. there you can see very good at first when the preload has been to less and later then when it was ok. sorry, just now no time to find this thread :(
     
  7. c4b4the04

    c4b4the04 Formula Junior
    Silver Subscribed

    Jun 9, 2017
    383
    Northern Virginia
    Full Name:
    Cassidy
    It is a long read but it is informative.
    https://www.ferrarichat.com/forum/threads/lost-all-gear-oil-today-1991-testarossa.621698/
     
    turbo-joe likes this.
  8. raysur

    raysur Formula Junior
    Silver Subscribed

    May 3, 2008
    561
    So. Cal.
    Full Name:
    Jeff
    #8 raysur, Sep 22, 2020
    Last edited: Sep 22, 2020
    I made the Ferrari tool.

    I used half a gallon of water to put the weight in the middle of their specs. I will upload the pdf artwork this morning.

    Here's the tool in action:
    https://photos.app.goo.gl/i2PkgGULnQEXnzQbA
     
  9. raysur

    raysur Formula Junior
    Silver Subscribed

    May 3, 2008
    561
    So. Cal.
    Full Name:
    Jeff
  10. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,868
    southwest germany and thailand
    Full Name:
    romano schwabel
  11. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
    241
    Full Name:
    Jon
    I’m familiar with the thread on Jamies testarossa, I’m the last person to post there. I just want to be sure we are all preloading correctly, that is why I want to be precise, it just feels like very little preload, nowhere near what the manual specs.

    Turbo Joe, can you give me more info on how you know it is too much?


    Looks nice Raysur, how did you arrive at the data for proper diameter and weight on the tool? Ferrari asks for 2kg measured on the pinion after setting propper pinion preload, so this would have to be multiplied by 3.21 or 3.75 or 3.9 depending on what gear ratio you have, so more like 7-8kg, no?
     
  12. raysur

    raysur Formula Junior
    Silver Subscribed

    May 3, 2008
    561
    So. Cal.
    Full Name:
    Jeff
    The Testarossa workshop manual states the weight in the differential section. The diameter was listed as 200mm in the tool list section. Before the torque specs.

    I just made the artwork with a pattern to attach to the axle hub. Using water was the easiest way to dial in the weight.
     
  13. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,868
    southwest germany and thailand
    Full Name:
    romano schwabel
    7 to 8 kg is really too much when F says only 2 kg
    and 0,5 mm is also too much. read the thread what you already have done, there I have written some. when I remember right 1/100 is increasing the preload about 0,15 kg. so 0,5 mm then is about 7,5 kg. have also a look in the WSM please

    this is not really correct. between the ratio you also have to count the resistance of the roller bearing and the gears with each other, also the complete weigth you will turn/move. and this what F says is only the pinion shaft without the mainshaft inside. because when you start from new you first adjust the pinion shaft.
     
  14. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
    241
    Full Name:
    Jon
    I guess you are all talking about specs in the testarossa wsm, which I don’t have.
    In the boxer wsm no preload is given for the diff alone, only the pinion (1.8-2kg), and then the diff in combination with pinion (3.6-4kg), both measured at the pinion with the tool.
    Could it be that the setup is different for the boxers? Or can it be an error in one of the manuals?

    Can anybody please post a picture of the testarossa wsm where the preload adjustment procedure?
     
  15. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,868
    southwest germany and thailand
    Full Name:
    romano schwabel
    I not think that there could be an error in the manual. the gearboxes inside are nearly equal.
    only thing is that they check in differnt way, bu tthis what is in the TR WSM sounds much better for me
    send you a PM
     
  16. Supernaut

    Supernaut Karting

    Dec 3, 2019
    146
    Annapolis MD
    Full Name:
    John Panek
    I've read all 4,287+ pages of Fchat threads on exploding diff carriers and diff setup and am trying to measure preload on my diff bearings and backlash of the ring/pinion now. No results to post yet, as my preload seems too high to simply rock the ring gear back and forth and get a good measurement. I'll lessen the preload and report back, as well as getting some paint to check the pattern.

    Some comments on mexicruiser's approach and raysur's setup above:

    Mexicruiser, I think you have a valid approach, but as Romano says you have additional friction from several bearings, gears meshing, and the axle flange seals. Perhaps you can remove the ring gear and measure all this independently to subtract out? But I see in your newer posts you've gotten it running and on the road. You ended up with a Modena diff and new LH cover? How did you end up setting them up?

    Raysur, in your video it looks like you had removed the ring gear? I don't think the WSM specs would apply then. There is some force from the pinion on the ring that you don't include?
     
  17. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    33,736
    Austin TX
    Full Name:
    Brian Crall
    It is all housed in a huge aluminum casting. If set at 60 degrees F and heated up to 90 degrees F you come up with a vastly different preload . I did not guess this, it happens. I have done it and measured it. At a real running temp of 175-200 degrees The measured number will be vastly different still and looser than I would ever set one up yet Ferrari gives us no guidance on what temp the measurements should be taken at.

    I did one in a cold shop and it was too tight. I put a heat lamp on it and went to lunch. When I got back it was too loose. I have been doing them based on judgement alone since. 75 or so BB/TR/512 transaxles later am still doing them that way.

    FWIW Ferrari is very specific about measuring the pinion shaft by itself and the carrier preload by itself. Any other way is for sure and invalid measurement.

    Test the gears on the drive and coast side.
     
  18. Supernaut

    Supernaut Karting

    Dec 3, 2019
    146
    Annapolis MD
    Full Name:
    John Panek
    Oh I believe you they loosen up a lot when heated. Aluminum thermal expansion is about double steel in this temperature range. My garage is ~40 degrees F, so I'll throw a heat lamp on the gearbox to see if it loosens enough for a backlash measurement. Still waiting on gear paint to check the pattern.

    Brian, your post confuses me a little with respect to the WSM.

    After the pinion is setup my 512BBi WSM says to:
    1) Coat gear teeth with the red lead paint
    2) Prepare LH and RH side covers and carrier for install
    3) Install 3 - 3.2 mm shim Z under bearing race of LH cover and install cover without seating on fastening surfaces
    4) Repeat for RH cover and gradually seat covers until backlash is 0.12-0.17 mm and preload is 3.9-4.0kg on the pulley tool.
    5) Rotate pinion and ring a few times and check paint patterns
    6) If patterns are good measure gaps between case and covers
    7) Install spacer Y under RH cover thickness equal to sum of gaps in step 6
    8) Decrease shim Z by the amount of the LH cover-case gap
    9) Torque everything up and recheck the pattern

    I don't see how above the carrier bearing preload is measured "by itself". It seems the ~4.0kg preload is a combination of pinion and carrier bearing preloads? Should I remove the ring as raysur did to measure the carrier by itself? I plan to remove it anyway to check for flatness and install a Newman carrier.
     
  19. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    33,736
    Austin TX
    Full Name:
    Brian Crall
    #19 Rifledriver, Jan 18, 2022
    Last edited: Jan 18, 2022
    You are taking any measurements and do not have the carrier that is going to be in it? Thats a complete waste of time.

    Whatever paint you are waiting for cancel the order. Use GM Gear Marking Compound. You can actually see it.

    The pinion is meant to be measured as a bare shaft with spacers taking the place of all gears and all bearings except the 2 pinion bearings and torqued.

    The carrier can be measured with no gear or no pinion....your choice.

    I read the BB book transmission section last back in the early 80s. Don't really remember it. Been working out of the TR book which supersedes it for the trans since it was printed and my notes from transmission school.
     
    turbo-joe likes this.
  20. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,868
    southwest germany and thailand
    Full Name:
    romano schwabel
    100% agree
     

Share This Page