Cleaning up my diff install | FerrariChat

Cleaning up my diff install

Discussion in 'Boxers/TR/M' started by qwazipsycho, Nov 2, 2015.

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  1. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    #1 qwazipsycho, Nov 2, 2015
    Last edited by a moderator: Sep 7, 2017
    Aloha,

    It's been a while since I was regularly posting here. A couple of years ago I tackled my exploded diff and posted the majority of the process (along with a complete gearbox teardown) on this site:

    http://www.ferrarichat.com/forum/boxers-tr-m/409047-installing-my-new-diff.html

    I spent about 6 months for the whole process including fabricating shims. When I finally got it finished, I wasn't completely satisfied with the ring and pinion mesh pattern on the coast side of the gear. It was perfect on the drive side and so close on the coast side I went with what I had out of frustration and it probably would have sufficed for most people. After assembling the diff, at the very end of the assembly process I discovered that I forgot about my crap clutch. The reason it's crap is another long story about letting others drive your car. It's posted somewhere on this site as well. Anyway, I assembled it with said crap clutch and regretted it. Not only was it glazed but it was out of balance and vibrated. I drove it quite a bit but eventually I parked it again and have only driven it around the neighborhood to keep her from stiffening up like an old woman. Now I've had the time, money, and facilities to clean up. Driving it helped me determine exactly what needed to be done to the diff.

    Don't get me wrong, I did a pretty fair job on the diff. Especially considering I've never done a diff before and I was dealing with aftermarket parts that were way out of spec (side cover). I usually leave those things up to those who do it for a living. But this is my F car and I wanna know her intimately in every way. There was a slight whine on deceleration as expected from the pattern. Most people couldn't hear unless I pointed it out. They also couldn't hear the slight growl when going around corners. But I could. And I'm too anal to live with that. I knew that sound probably meant not enough preload on the diff. Couple those things with the vibration from an out of balance and glazed clutch and the car was not fun to drive anymore.

    Problem solved. This time I did the job while it was still in the car. And if I ever do another diff, I will do it this way. It's very simple. And the fix? It was equally as simple. I added a .15mm shim to the left side cover. That gave the gear swipe pattern a PERFECT mesh on both coast and drive side. It also added enough to the preload that I'm sure the growling around corners will be gone. A very slight adjustment and it feels and looks perfect.

    Now, I get to install this beautful rebuilt and PRECESION BALANCED clutch from ClutchMasters. I should be back to enjoying the drive again within a few days.

    I've missed chatting with you all, Romano, Kerry, SteveM, and many others, and your brilliance and support.

    Mahalo,

    Scott
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  2. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,867
    southwest germany and thailand
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    romano schwabel
    I hope that this 0,15 mm shim will solve the whining from the diff?
    but with this shim you will have now more preload to the bearings. may be when you did the job before that the preload has been not ok? or the bearings moved a little???

    good luck scott
     
  3. dwhite

    dwhite F1 Rookie

    Good luck Quazi, Now you can go out and blow the doors off AllanLambo. ;-)
     
  4. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    Something I noticed about that CHEAP aftermarket left side cover. (I will not buy another from them) is the hole for the bearing race cup is too big. I think the mfg intended that knowing that setting up the diff requires repeated removal of the bearing race and instead of modifying a race to use for setup, they simply gave it clearance for easier removal of an unmodified race. However, when the race is installed, I can spin it with my hand. There's no side to side play but it's not completely an interference fit the way it should be. I was considering putting a "knotch" in it with a hammer and punch but I chose not to hoping that the preload pressure will keep it from moving.
     
  5. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    2,772
    Was lash good. Could you feel some clearance before and now (after new shim)?
     
  6. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    Lash is good, however I learned not to be too concerned with excessive backlash. I'm using used gears so there is going to be some wear. Final backlash is about .009". I believe spec is .004 to .007. I'm not worried about it. If I remember the manual correctly, there is some room for wear that you can add to those numbers. If that pattern is good, I say go with it.
     
  7. tf308

    tf308 Formula 3

    Dec 14, 2003
    1,168
    Virginia Beach
    Full Name:
    Tim
    For all of us unassuming dumbies out here.....

    Can you show how you measured back lash? More pics.

    How did you measure the preload torques? etc, etc
     
  8. Melvok

    Melvok F1 World Champ
    Owner Silver Subscribed

    Jul 25, 2008
    14,101
    Amersfoort, The Netherlands, Europe.
    Full Name:
    Mel
    :D !
     
  9. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    Sorry gents. She's already back together. As far as measuring backlash, I just made a little rig to bolt to the bottom of the case using the studs. Attached an analog micrometer to that and pointed it at the heel side of one tooth. Grab the ring gear and wiggle or attach an axle flange and wiggle.

    I measured preload initially using the fish scale method. I felt that the prescribed weight was a little light and it showed while driving. After adding this very small shim to my existing setup, I used the "feels good" method. In other words, I felt the preload before the shim and after the shim it felt good. A bit more resistance but not too much. Only driving it will tell if it was enough to make that little growl go away.
     
  10. Chief20123

    Chief20123 Karting

    Dec 22, 2012
    169
    Melbourne,Australia
    Full Name:
    Fred
    I'm in the process of measuring preload. using the fish scale method as well. You mentioned 9-10 lbs of force in previous thread? approx. how many lbs would it be it be now, after your change?
     
  11. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    I would give it a pound or two more. It's really a matter of feel. If you know what a good bearing preload feels like in other diffs, that's what I was going for.
     
  12. Chief20123

    Chief20123 Karting

    Dec 22, 2012
    169
    Melbourne,Australia
    Full Name:
    Fred
    Scott, you said you added a little shim (to outside LH cover). wouldn't this reduce preload ? not increase ?
     
  13. Chief20123

    Chief20123 Karting

    Dec 22, 2012
    169
    Melbourne,Australia
    Full Name:
    Fred
    that should be RH cover (my diff is upside down)..
     
  14. Chief20123

    Chief20123 Karting

    Dec 22, 2012
    169
    Melbourne,Australia
    Full Name:
    Fred
    ignore my comments above...I understand now. by adding a shim to LH side cover. backlash is decreased and preload is increased ?
     
  15. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
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    Scott
    HA! Too funny Fred. I had my gearbox upside down to do the rebuild too. I had to etch it in my brain that the big side cover is left.
     
  16. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    You are correct.
     
  17. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    I finished up the new clutch install and diff adjustment and took it for a spin. Finally. Ahhh I love this car....

    MOST of the problems were solved. The whine from the diff on decel is gone. The vibration from the clutch being out of balance is gone. (Thank you ClutchMasters!)

    HOWEVER, I have a horrendous amount of diff chatter. I thought the majority of the chatter I had initially was coming from the glazed clutch. But now, the clutch is perfect and this diff seems to be where all the chatter was coming from in the first place.

    If I launch in a straight line and keep going in a straight line it's perfect. But the second I turn, that diff sounds like I'm driving a front wheel drive car and I've got a bad CV joint, at least at low speed. At higher speed it growls.

    The rest of the gearbox is perfect. Shifting is smooth and easy.

    The small adjustment I made to the diff brought it to perfection as far as the gear setup and preload. I got a perfect swipe pattern for the first time and it was evident while driving today. No more whine on deceleration. But, I think that adjustment made the diff chatter a bit worse or at least more obvious.

    I've never had to use additives to my gear lube before. But then again, I've never had this diff in this car before. Maybe some limited slip additive will help but if it can remove the problem, I'll be a firm believer.

    UPDATE: I added 4oz of the GM LSD addititve. I drove it about 2 miles and noticed no change.

    This chattering is so bad when I launch at an angle the whole car shakes.

    I've been talking with Philwozza and Newman and both recommend trying the LSD additive. Everyone here swears by Redline but it's not available on the island here.

    I just find it hard to believe that a different oil can make that much difference. If this were just a minor chatter, maybe, but this is really bad.
     
  18. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,867
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    romano schwabel
    try to find castrol 75W140 LSD, then you don´t need redline
     
  19. mikael82

    mikael82 Formula Junior

    Nov 18, 2007
    869
    Finland
    Full Name:
    Mikael
    Normally with daily driver, there is no need to change gearbox oil, as often as you might think, but with BB diff/gearbox I have found that because diff and gearbox are using same oil, there seems to be more debree floating with gearbox oil and I would change oil from these more often.
    What I would/did do; after diff change, I would change oil even more often, kind of "drive in" oil.
     
  20. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    Well I drove it for real today. About 15 miles round trip down and up my curvy mountain road. The longer I drove the less I noticed the chatter and growl. It seems that the GM additive is working but I don't think 4 ounces is enough. There are 10 to 11 qts of oil in this gearbox. I think those 4 ounce bottles are meant for a diff without a gearbox holding 3 to 5 qts. I'm going to try another bottle of the GM stuff (If I can find one. I bought the last one on the island last week.) and see if that doesn't resolve the problem altogether. If it doesn't but comes close, I'm going to drain $90 worth of brand new Valvoline into the recycle bucket and replace it with $300 worth of Redline....I just keep telling myself, "you saved 10's of thousands of dollars by doing this job yourself. You learned highly valuable information about your car. She's back on the road and you're almost finished...at least with this job."
     
  21. Melvok

    Melvok F1 World Champ
    Owner Silver Subscribed

    Jul 25, 2008
    14,101
    Amersfoort, The Netherlands, Europe.
    Full Name:
    Mel
    Any other diff experts can tell us (the community I mean) what causes the "chatter" ... I have no clue ...

    Is it a whine at turns of the car ?
     
  22. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
    8,867
    southwest germany and thailand
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    romano schwabel
    the "chatter" is when the plates inside the diff for the limited slip are rotating when you go a turn, straight on the diff is not working and so no chattering
     
  23. qwazipsycho

    qwazipsycho Formula 3

    Oct 30, 2004
    1,176
    Utah
    Full Name:
    Scott
    Aloha Mel,

    Picture a clutch attached to each axle. When each axle is spinning at the same speed the clutches stay locked up so straight line driving isn't an issue. When you go around a corner, one is spinning slower than the other so it has to slip the clutch. Since these are "static" clutches there is no release mechanism so the pressure on the clutches has to be just right to allow that slower axle to slip the clutch. If the oil in the diff isn't "slippery" enough the clutches grab and slip instead of just slipping. That causes chatter. The additive I'm putting in is a friction modifier that makes the oil more slippery.

    Note that the chattering is much worse the slower you're moving and can make it feel unstable as it hops around corners sometimes.
     
  24. Philwozza

    Philwozza Formula 3

    Apr 23, 2009
    2,045
    Winchester UK
    Full Name:
    Phil Worrall
    It something I call slip stick.
    Try squeezing your first finger to your thumb. Then move the two across each other. They don't move smoothly, they stick a little then slip and the process repeats, this we call chattering.
    A slip modifier adds a little more lubrication that the normal oil provides thus minimising or completely resolving the chattering. The best oil I have found and backed up by lots of other Testarossa experts is Redline. For me it just works out of the bottle first time.

    Phil
     
  25. mikael82

    mikael82 Formula Junior

    Nov 18, 2007
    869
    Finland
    Full Name:
    Mikael
    is it straight NS Redline or blend with regular and what weight oil is best?
     

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