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Thread: 901 Trans Intermediate Plate Gasket Thickness

  1. #11
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    Retired in the Seattle area.
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    Yes, Stoddard have the case to intermediate plate gaskets in 0.1mm, 0.15mm and 0.2mm. Sierra Madre and several other vendors do as well.

    Unfortunately it looks like the side cover gaskets may only come in one thickness - Stoddard only have one shown - 901.301.391.01 (original #) which supersedes to X.02. And I do not see anything different from other vendors. I am going to call Stoddards Tuesday morning and check on the thickness and see if they have a 0.1mm side cover gasket or know where I can source one. Using a 0.22mm side cover gasket, that is 0.1mm thicker than what was there to start with, sounds like a problem to me. So I may have to find someone with the tool and re shim the differential. Or purchase some 0.1mm paper gasket material and make a side cover gasket. Tedious, but probably quicker and a lot cheaper than re shimming the differential. If anyone knows where to get side cover gaskets in different thicknesses please let me know.
    Bill Sargent
    Seattle area
    67 912
    64 356 C cab
    59 356 A carrera cab
    64 904 in the works

  2. #12
    Member
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    Feb 2013
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    Retired in the Seattle area.
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    33
    I have another question. The transmission is a 902/1 five speed out of a 67 912 - original to the car which was built in November 66. The axel flanges are connected to the differential with the early type stretch bolts with no tit on the end. This is the type of axel flange that has an aluminum cover over the stretch bolt head. The aluminum cover is held in place with a large wire circlip. Under the head of the stretch bolt is a thick washer with a flat on one edge to locate it. I cannot find the torque value for the stretch bolts in the shop manual. I have read on line that this type of bolt with the washer underneath is torqued to 20 ft lbs and the later (915?) type bolts with the tit and no washer are torqued to 30 ft lbs. Is 20 ft lbs correct for these bolts? And are they reusable? Or do I need to spend $55 each for two new bolts?

    Note - these are not the stretch bolts that connect the Lobro half shaft CV joints to the axel flanges. These are the bolts (one on each side) that connect the axel flanges to the differential.

    Any definitive info on the stretch bolt torque would be greatly appreciated.
    Bill Sargent
    Seattle area
    67 912
    64 356 C cab
    59 356 A carrera cab
    64 904 in the works

  3. #13
    Quote Originally Posted by Bill Sargent View Post
    The axel flanges are connected to the differential with the early type stretch bolts with no tit on the end... Under the head of the stretch bolt is a thick washer with a flat on one edge to locate it.
    I cannot find the torque value for the stretch bolts in the shop manual.

    I have read on line that this type of bolt with the washer underneath is torqued to 20 ft lbs and the later (915?) type bolts with the tit and no washer are torqued to 30 ft lbs. Is 20 ft lbs correct for these bolts? And are they reusable?

    Any definitive info on the stretch bolt torque would be greatly appreciated.
    Bill, the torque value is in the factory specs booklet, page 68:
    "Stretchbolts for half-axle U-joint flanges, M10 ................. 4.5-5.0 mkp"
    This equates to roughly 45-50 Nm, or 32-37 lb-ft of torque.

    This applies to all flange bolts through '67, except for the ZF limited-slip bolts, and both 911 and 912 models.
    The torque value listed in the '69-'71 specs booklet, for the simplified differential bolts, is 3.5-4.0 mkp.

    Note that the bolt head fastens against the differential tube, and not to the washer, which should be free to float.
    In my opinion these bolts are fine to re-use if not distorted, elongated or damaged.

    Jon B.
    Vista, CA

  4. #14
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    Feb 2013
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    Retired in the Seattle area.
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    33
    I have a question about the diff side cover gasket.

    I understand the diff set up process from the shop manual as follows. Starts with 0.2mm diff cover gasket and needing 0.15mm clearance between the case and cover/gasket for preload, without the cover bolted down. Then you adjust the S1 ans S2 shims on both sides of diff to get the correct preload measurement. Then bolt cover down with 0.2mm gasket and measure backlash. Then Adjust the S1 and S2 diff shims again to get correct backlash - which I would think almost certainly changes pre load clearance. So what does Fritz on the assembly line do? Take the outer bearing off again and replace the shims again to adjust the cover clearance for correct pre load with the 0.2mm gasket? No, Fritz gets a thicker or thinner gasket for the diff side cover. And moves on to the next transmission. But today only the 0.2mm cover gasket is available.

    So, if I understand this process correctly, when rebuilding, you have to take the bearings off again to get the pre load correct with the 0.2mm gasket since that is the only thickness available. If all you are doing is a reseal, and the cover gasket is not 0.2mm, you either change the shims to get correct pre load with a 0.2mm gasket or you make a gasket of the required thickness.

    Do I understand this correctly or am I missing something? If I do understand it correctly, is there a source for different thicknesses of diff cover gaskets? The parts book only lists one diff cover gasket (compared to 3 different thicknesses of intermediate plate gaskets). And Paul at Stoddard confirmed this morning that they only have the one diff cover gasket.
    Bill Sargent
    Seattle area
    67 912
    64 356 C cab
    59 356 A carrera cab
    64 904 in the works

  5. #15
    Quote Originally Posted by Bill Sargent View Post
    Then Adjust the S1 and S2 diff shims again to get correct backlash - which I would think almost certainly changes pre load clearance.
    So what does Fritz on the assembly line do? Take the outer bearing off again and replace the shims again to adjust the cover clearance for correct pre load with the 0.2mm gasket?
    No, Fritz gets a thicker or thinner gasket for the diff side cover. And moves on to the next transmission. But today only the 0.2mm cover gasket is available.
    Bill, as long as the sum dimension of S1 + S2 + gasket remains constant, then the preload doesn't change.
    If you increase the S1 dimension, then you decrease the S2 dimension by the same amount.

    There was never a selection of cover gasket sizes, but over the years there have been some differences. The assembly line scenario you suggest didn't occur- the adjustments were all made through S1 and S2.
    If using a new gasket in a different size, you can check the bearing preload and ring gear backlash to see if they're still within an acceptable range.
    Otherwise, if you're just trying to keep everything as it was, then you might need to make a new gasket in the size you need.

    Jon B.
    Vista, CA

  6. #16
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    Feb 2013
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    Retired in the Seattle area.
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    Closing the loop on this thread. Since the transmission was shifting well and not noisy I elected to try and keep the side cover gasket thickness as I found it at about 0.13mm. This is thinner than the only available gasket at 0.2mm. I was unable to find paper gasket sheet stock in different thicknesses. But I was able to find sheet polyethylene shim stock which comes in a wide range of thicknesses. I used 0.0005 inch which equals 0.0127mm. After making a new side cover gasket from this shimstock, I installed the side cover with a little Curil T on both mating surfaces. After a couple of thousand miles everything is good. Transmission shifts well, no noises and no leaks.
    Bill Sargent
    Seattle area
    67 912
    64 356 C cab
    59 356 A carrera cab
    64 904 in the works

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