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BBi Major +

Discussion in 'Boxers/TR/M' started by mexicruiser, Sep 25, 2019.

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  1. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Jon
    I don’t like the idea of full thread bolts to hold flywheel or ring gear, too much shear, no? Not many options, ARP has some for a vauxhall application for the flywheel but these have a 3/4 head and wouldn’t fit.
     
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  2. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    romano schwabel
    0,5 mm I also would say is too much

    the pattern looks great :)
    why not remove the crown and put in the diff again with the shims as they are just now and measure with a fish scale the preload?

    I also used ARP screws, I think from a toyota they are nearly the same, only 1 mm too short but this I accepted
     
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  3. mexicruiser

    mexicruiser Karting

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    #28 mexicruiser, Aug 18, 2020
    Last edited: Aug 18, 2020
    You are right, the bolts for toyota are 1/2 head bolts and 1.35mm shorter, but then you also remove the locking tabs, these measure 1mm so en reality the bolts are only 0.35mm short. This is the ticket.
    These could also work on the flywheel if ground to length (25mm) or if there is space behind the crankshaft flange for the 1.65mm extra length (with spacer shim) or 2.65mm (without washer as per ARP instructions. Does the flywheel shim count as a washer?
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  4. turbo-joe

    turbo-joe F1 Veteran

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    I would say: yes
     
  5. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Yesterdays progress:
    -Swapped the bearings from the original carrier onto the new modena eng diff. tried the heating method but got stuck, then used my press, didn’t require much pressure to fit them. Installed these on the same side as removed.
    -Torqued the carrier cap bolts to 30lbs/ft in crisscross pattern, then one by one removed the bolts (crisscross) put a drop of red loctite and torqued to 40lbs/ft (consulted with them on the torque specs).
    -Mounted the crown/ring gear provisionally using the old bolts torqued to 30nm (spec is 69nm) using two steps in a crisscross pattern.
    -Installed LH diff support to 32nm. In two steps to a crisscross pattern
    -Installed RH diff support with original shim plus .013” feeler gauges at 120deg using only 3 nuts tightened until the feeler gauges were tightly clamped. This additional gap produced a barely non-freewheeling-when-hand-spun-and-let-go carrier (tested previously without crown/ring gear). Call me chicken but I didn’t dare to tighten only three nuts for fear of cracking/deforming the unsupported flange.
    -Measured backlash with a dial to be .14mm or .0055”, old spec was .15mm or .006” so lost .01mm to the new diff.

    In theory being that backlash is still within tolerance, I could check gear mesh and if correct just get a thicker outer shim to fix preload. I suspect the crown/ring gear bolt torque is not going to change much, but torqueing the RH diff support to spec could tighten things up a bit.
    So now I have the following to find out:
    -How much will having the crown/ring gear bolts to 30nm effect backlash
    -How much will having the RH diff cover/support to a lot less than 32nm effect backlash and preload

    Also on the carrier preload I think things could get pretty loose when operating temperature is reached, I wish I had tested the original diff for non-freewheeling-when-hand-spun-and-let-go .
     
  6. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Is the flywheel cast or forged? I ask because I have a friend who is an expert on metallic material engineering, he explained that if the flywheel is cast steel the hardened forged steel bolts can cause microabrasions when tightened directly onto the surface, leaving stress risers that can cause component failure, this is why a shim is used instead of washers, the shim doesn’t spin.
    I will ask ARP on their opinion on this.
     
  7. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    why you put the crown on the diff before adjusting the preload of the bearing from the diff???
    and before you may check the backlash you may check the preload of the diff ! ! ! and this you only can do without the crown on the diff
     
  8. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    I adjusted preload provisionally using the non-freewheeling-when-hand-spun-and-let-go method others have used, shimming the RH diff cover with feeler gauges for adjustment, the crown was off for this.
    I had to check backlash because spending money to make a RH spacer without making sure backlash is ok would be a waste.
     
  9. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Did some more checkin’ today, just to be surer*...

    My main concern was I checked preload using .013” feeler gauges and only limited torque (about 8-10nm) on the RH cover, I suspected when properly torqued the measurements would change.
    I followed advise given by on P32’s diff explosion thread and fabricated paper shims to torque to spec and see what would happen.
    I made a thick paper replica of the original RH shim (outer) and added thin paper clippings to distribute the load and reduce the risk of damaging something. The thick paper shim measured 0.010” and the thin clippings measured 0.0038”. When tightening to final torque values the results where as follows:
    -Backlash 0.007” or 0.178mm which is greater than the oem diff at 0.15mm
    -Preload was very much ok by the non-freewheeling-when-hand-spun-and-let-go test

    The added backlash is probably a result of the .0008” extra thickness of the paper vs the feeler gauge (Backlash was .0055” when measured with .013” feeler gauges)

    so I removed the thin 0.0038” paper clippings and left the 0.010” paper shim and rechecked, the results where:
    -backlash .0.006 or 0.15mm which is the original diff setting.
    -checked pinion mesh and results were nice, pretty similar to the original setting.
    -Preload was pretty tight so I tested spin torque with a small scale torque meter, this resulted in 4-6nm to keep spinning after starting to spin. Tight, have to grab the diff and flange to start spinning, then it becomes easier.

    so, I think I’m more comfortable with higher preload than with less, because I would be concerned with the crown moving off the pinion under load, also the original preload was somewhat high. Now I need a thicker RH shim original is 1.295mm (1.3mm?) and need a 1.55mm (not listed on the catalog).
     
  10. mexicruiser

    mexicruiser Karting

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  11. mexicruiser

    mexicruiser Karting

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  12. mexicruiser

    mexicruiser Karting

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    #37 mexicruiser, Aug 21, 2020
    Last edited: Aug 21, 2020
  13. turbo-joe

    turbo-joe F1 Veteran

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    that are 2 very positive things: diff from modena is complete and LH cover ok :)
     
  14. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Digging deeper, I had seen non original silicone on the drop gear cover and decided to take a look, it seems whoever changed the clutch on this car also disassembled the clutch shaft using a chisel on the nuts.
    My theory is the car sat too long and water rusted the clutch parts, when trying to get it running to sell It they had to remove the shaft to get the bellhousing off for the clutch replacement. Good that I saw this as the nuts are not properly torqued.
    I need two new ring nuts, hope these are still available, and the tools or maybe these too can be fabricated like I did with the timing gear ring nuts?

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  15. turbo-joe

    turbo-joe F1 Veteran

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    yes
     
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  16. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Updating:
    I’m finishing work on the transmission and diff, after replacing the shift shaft seal and silentblock I instaled the detent balls and springs, fabricated a steel retainer for these and also machined an alignment pin, (I tried using a cam pulley locating pin as Bendl did when he did his major but I felt this allowed too much movement, as it is missing the lower part that fits in the case). After engaging second gear the shift shaft selector bolt is loosened and the selector is adjusted so it is centered on the 2-3 fork (equal gap to the other two forks).
    While I’m here I decided to remove the oil sump cover and have a look, found a small piece of thin aluminum in there, not sure where it came from, cleaned the area and removed the gasket material, this part was very difficult, the gasket was adhered to both sides and is rock hard (probably asbestos fibers?), it took me many hours with razors (with risk of damaging the aluminum) paint remover (with risk it of dripping onto the engine paint inside), sand paper (320 grit as 400 didn’t seem to have any effect), and finally abrasive pads. i searched around here for sealant recomendations and decided to use a thin strip of hondabond, now even with a 1/8 thin strip I got a little excess pressed out so I’m a bit concerned but I am hopping its not a problem, the oil passes thru the filters first right? I would have liked to install the gasket dry to ease removal but with the amount of work it took to get the original gasket off I think it might be even easier with the hondabond.

    I am now at the new diff (Modena Eng) preload setting and currently getting a new 1.55mm RH shim (Turbo Joe is helping me out here with a blank thank you) for the LH one I‘m using a 0.005” Dana 60 shim on top of the existing one.
    The preload issue has had me doing all kinds of experiments (I posted this on another thread) and I think it comes down to different options depending on situation.

    Option A: measure existing preload before replacement and target the same spec (this should only apply if reusing your old bearings and if you are replacing an intact diff)
    Option B: restore preload to WSM specs (applies to either new or used bearings but its a LOT of clamping force)
    Option C: Set preload to an aproximate figure by hand feel, (able to turn by hand and doesn’t keep spinning on its own) or by rope on the carrier body and weight (different opinions and approaches on this forum)
    Option D: a mix of the above? a different process?
     
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  17. mexicruiser

    mexicruiser Karting

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    At 700km my car has extremely low mileage and the diff replacement is preventive, I’m also reusing the stock bearings so option A i is possible or I could use option B with a lower than spec value. On removal my diff preload gap on the RH side cover was between 0.019” - 0.021” (lets say 0.020”) so per manual procedure setting backlash first and then preload I had to add 0.005” to the LH shim and also need a thicker 0.061” RH shim (currently 0.051”) to fit the new diff and keep the same preload.

    On a side note it is my opinion others are risking R&P failure if using new bearings and adjusting it to turn by hand (op C) or readjusting to stock (op A), once the new bearings break in and the transaxle heats up and “grows” (at high speeds) the little preload will be lost and the pinion will push the crown away.
     
  18. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    have never read the manual right, but when you adjust backlash first and then the preload the backlash is changing again. you first may adjust the preload and then the backlash by removing or adding same size of shims thickness both sides to keep the prelaod
     
  19. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Yes Romano, this I also think is required for fine tuning, as the case+covers might not deflect equally.

    The manual states to adjust backlash by installing a large LH shim and no RH shim, then moving the covers in/out By threading the nuts without tightening until desired backlash is achieved, then measuring the gaps on both sides and reducing these equally until preload is achieved, measuring again to determine correct size for both shims.
     
  20. turbo-joe

    turbo-joe F1 Veteran

    Apr 6, 2008
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    as I have written already:
    I adjust first always the preload with left side a thick shim.
    once the preload is adjusted it is only some work to adjust the backlash. this size of shim thinner on the left side you als need thinner on the right side
     
  21. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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    Updates: fabricated a new 0.061” RH diff cover shim (was 0.051”) to adjust preload and to finish adjustments on the new Modena Engineering diff.
    Disassembled the new diff and rearranged friction plates to oem configuration and set the locking ramps for milder locking action, this diff is basically a replica of the original diff without the infamous weld, and with the added benefit of being able to choose from two different locking ramps.
    I installed the crown using ARP bolts from a Toyota flywheel application (Romano shared this tip, thank you) the bolts are a bit shorter but this was compensated because I scrapped the locking plates, I used red threadlocker on the threads and arp lube under the bolt heads, tightening down to 70 lbs/ft as instructions from ARP.
    Tested preload was measured with a 0-6Nm needle torque wrench on the prop shaft, fitted using a 22mm 12pt socket over a shop towel to protect the splines. Turning resistance oscillated between 1.5 and 2.5 Nm for a 2Nm average which is a bit lower than the calculated ideal of 2.3Nm.
    Backlash was measured by fitting an extension to the rh diff output flange, on a point equal to the crown diameter, this was done so because measuring directly on the crown requires installing the dial at an angle giving inacurate readings. Readings were in the 0.005” to 0.006” range.
    Finaly gear mesh was confirmed with paint on the crown resulting in a pattern closely resembling the original pattern obtained before disassembling.
    Was ready to instal the seals on the covers to wrap things up but discovered the new seals I got for ferrparts are direction specific and both for the same side, also narrower, will see if I find a better replacement locally tomorrow, the new orings for the covers are also not quite correct, a bit too large.
    I had read on this forum several members do not reuse the wavy washers for the covers and the engine to transaxle, I should have changed these, some already snapped during the setup.
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  22. mexicruiser

    mexicruiser Karting

    Aug 28, 2012
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  23. mexicruiser

    mexicruiser Karting

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    Fabricated side cover shim, this was plasma cut except the holes I made with a drill.
    ARP bolts 203-2802 for Toyota I used on the diff, these bolts will also be used on the flywheel, I checked with their tech dept. and they said I should reuse the steel shim, just be shure the holes are large enough to clear the chamfer on the bolt heads.
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  24. mexicruiser

    mexicruiser Karting

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    I wonder if this pieces are original or fabricated to repair a worn set? I find the shaft and lever to be very different than what I have seen in this chat, has anyone seen this type on the later boxers (1983-1984)?
    The shaft does have a small splined section but the lever is a flat steel plate welded onto the shaft end. The shaft itself is stepped down straight to the splined end so the usual forged lever wouldn’t fit properly.
    The fork shaft outer bearing was rusted and the shaft wouldn’t move so I used acid and wd40 to get it going again, I removed the clutch input shaft because it will be needed for clutch alignment and to replace seals along the way, also because the ringnut was badly battered and I have a new one.
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  25. pshoejberg

    pshoejberg Formula 3
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    That clutch lever looks to be identical with my late 1984 BBi. I had no issues with fit but had the the same seized needle bearing. I changed out the needle bearing to a model with a small rubber lip seal. All you need for the repair is a 15$ bearing + 2 new conical steel pins for the release fork (These will most likely suffer damage when removed).

    Best, Peter

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