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  1. #1
    Join Date
    Jun 2007
    Location
    Cape Cod, MA, USA
    Posts
    451

    Default Shimming Lower Unit to Intermediate - DP

    I know this topic has been discussed often, but during assembly I began to second guess myself. I always thought you wanted to have a clearance, or 'negative' preload between the lower unit tapered roller bearing and the race pressed into the intermediate housing.

    After taking numerous measurements, I have confidence in the height of the race placed over the lower unit tapered bearing -aka "A" according to Volvo, and the depth of the intermediate housing where the race is pressed - "B".

    B is greater than A.

    The manual (DP-E) states: "add 0.02 mm to the clearance dimension to establish preload." See below:

    Click image for larger version. 

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    I do not feel comfortable preloading this tapered bearing. It will spin at +3700 RPM at WOT and I suspect this angular velocity will create significant heat, which will lead to expansion thereby creating greater friction, aka heat.

    I plan to create a shim stack that will leave a clearance / void / slop, between the tapered bearing and race by 0.020- 0.030 mm.

    Can you guys weigh in here?

    My math is:

    B = 8.0340 mm
    A = 7.4828 mm

    Clearance = 0.5512 mm

    In theory, a 0.5512 mm shim stack would create zero preload. Creating a shim stack GREATER than 0.5512 mm creates a POSITIVE preload and creating a shim stack LESS than 0.5512 mm creates a NEGATIVE preload.

    My intent is to create a shim stack between 0.5258 - 0.5131 mm.

    Rummaging through the shims on my bench I cannot achieve this, so I will place an order. Evidently Volvo only sells shims in the following thickness: 0.05 / 0.10 / 0.20 / 0.35 mm.

    So it looks like my stack will be: 0.35 + 0.10 + 0.05 = 0.50 mm. Maybe they will mic out a bit thicker and I can achieve the desired 0.52ish.

    Thoughts?

    Thank you.

  2. #2
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,545

    Default Re: Shimming Lower Unit to Intermediate - DP

    My calcs are .57mm will give you slightly under .02 mm preload. .57mm is .0224 inches
    8.0340 - 7.4828 =.5512 +.02 = .5712
    Wait for word from Ricardo if your measurements are accurate you want around .57mm from what I see
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  3. #3
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,193

    Default Re: Shimming Lower Unit to Intermediate - DP

    Switch to inches and I'll be able to help you.

    Also, when you take either the A or B dimensions, take up to 6 or 7 readings around the perimeter.
    Use the reading that you see most consistently.


    And Mike...... are you running an E drive behind Diesel power?


    .
    Last edited by RicardoMarine; 08-13-2017 at 08:27 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

  4. #4
    Join Date
    Jun 2007
    Location
    Cape Cod, MA, USA
    Posts
    451

    Default Re: Shimming Lower Unit to Intermediate - DP

    Thank you kimcrw, Ricardo - your help is appreciated as always.

    I took 8 measurements around the circumference of 'A' and 'B', and repeated the sample set 4 times. The results:

    B =0.3163"
    A = 0.2946"

    B - A = 0.0217" = clearance fit

    I assumed I had a DP-E drive because the prior owner stated so. Doing research last night, I no longer believe so. The lower unit exhaust vent does not match a DP-E, and the upper unit drive gear / u-joint yoke bolt is an Allen head, not torx.

    I then looked up the DP-A/B/C Volvo manual and read this:

    Click image for larger version. 

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    This verbiage differs slightly from the DP-E manual. It states: "a clearance dimension of 0.0008" shall be aspiring to attain" and the max allowed clearance dimension is 0.002". So if I am reading this correctly, the math is:

    Shim for max clearance = 0.0217" - 0.002" = 0.0197"
    Shim for "aspiring clearance" = 0.0217" - 0.0008" = 0.0209"

    For anyone reading this now, or in the future, when building their drive, I will define what preload means to me. Ricardo, kimcrw, let me know if I am interpreting properly:

    When the intermediate housing is secured to the lower unit (final assembly), two potential scenarios will exist:

    1. If the 'A' dimension + shim pack is greater than the B dimension, the race pressed into the intermediate housing will impart a compression force on the lower unit tapered bearing resulting in a POSITIVE PRELOAD.

    2. If the 'A' dimension + shim pack is less than the B dimension, there will be a clearance (gap, void) between the race and the lower unit tapered bearing and no compression force will be applied. This is what I am calling a NEGATIVE PRELOAD.

    From what I see, Volvo sells four shims, thicknesses: 0.0020", 0.0039", 0.0079" & 0.0138".

    I will try: 0.0138" + 0.0039" + 0.0020" = 0.0197" and hope the stack is lightly thicker than theoretical.

    It also donned on me last night if the prior owner did not shim the new lower to the old intermediate, then there is little to no chance the lower unit tapered bearing and intermediate housing race are a matched set. How undesirable is this, and what would the negative impacts be?

    Thank you for the help!!

  5. #5
    Join Date
    Dec 2015
    Location
    maplevalley WA
    Posts
    3,545

    Default Re: Shimming Lower Unit to Intermediate - DP

    It looks to me like you want to replace the two bearings on the verticle shaft and recalculate the shims. You are over .020" clearance for the shims. You will also need to check gearlash but in general the bearings have very tight tolerances and just putting in new bearings should get it close enough. Adding shims will work for a bit but if the bearings are going bad you can destroy the gearset rather quick.
    Last edited by kimcrwbr1; 08-13-2017 at 04:08 PM.
    It takes a nickle to go first class!
    If it aint broke dont fix it!!

  6. #6
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    9,193

    Default Re: Shimming Lower Unit to Intermediate - DP

    Please re-read the instructions. Pay close attention to "Pre-Load" -vs- "Clearance"!
    Make sure that you have held the tapered roller bearing race fully and evenly down and into the roller cage.
    Take many A dimension readings.
    Also take many B dimension readings.


    Pre-load may not exceed .0008"..... that's 8/10,000 of one inch!
    Clearance may not exceed .002" ........ 2/1,000 of one inch!



    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

    Please... no PMs! Post your questions on the forum.

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