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E21 Transmission Mounts

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    DIY: E21 Transmission Mounts

    Original poster - Tbonem3

    "These instructions are only as a guide for people to replace their transmission mounts with E21 transmission mounts. Please read through all the instructions before attempting to install on your own. I take no responsibilities for any inaccuracies or problems/damage /injuries you may encounter from using these instructions. Please consult your shop manual.

    E21 transmission mounts are a bit stiffer than the OEM transmission mounts. They are cylindrical in shape, similar to the Rouge Engineering mounts, but for significantly less cost. Some modifications will need to be made though. The E21 mounts use M10 thread rather than the M8 on the stock mounts. This means that there will be some modification required on the transmission mount brace, counter weight, and part of the threads on the E21 mount (see below).

    Parts required:
    2x E21 Transmission Mount, OEM Part # 23711246004 - You can use OE (Febi) 23711109173 ($4.95 ea)
    4x M10 Nut - The cheapest found on FCPEuro is a Porsche Nut, Part # 971098 ($0.39 ea)

    Tools required:
    8mm socket
    10mm socket
    E12 socket
    13mm socket/wrench
    15mm socket/wrench
    Drill with drill bits large enough to create 10mm hole
    Jack & Jack Stands / Lift

    1. Raise the car and place on jack stands. Never work on a car that is only supported by a jack.

    2. Remove the under-trays covering the transmission cross brace. They are secured with a series of 8mm nuts and screws.

    3. Remove section 1 of the exhaust. This piece runs between the header and section 2, it is approx 3 feet in length. The exhaust needs to be removed to gain access to the transmission cross brace.
    A. Remove (4) 15mm bolts that connect the exhaust to the headers. (use penetrating lubricant to help loosen bolts, they'll be really tight). One side of these bolts are an E12 Torx.

    B. Remove (6) 13mm bolts connecting section 1 to section 2. Keep track of the bolts, nuts, and gaskets. They will be reused.

    D. Support both ends of the exhaust before removing the final bolts holding the exhaust. Exhaust will fall when you remove the final bolts. Move the exhaust towards the rear of the car to remove from headers.

    4. Remove exhaust heat shield covering the transmission cross brace. This is held on by a series of 10mm nuts and screws.

    5. Place a jack on the rear of the transmission to support it. Be sure to leave space so you can still access to transmission cross brace and transmission mounts.

    6. Remove (4) 13mm bolts on the transmission cross brace. There are (2) on each side connecting it to either side of the transmission tunnel.

    7. Remove (2) 13mm nuts for the transmission mounts. Remove cross brace.

    8. On the top of the mounts, use a 13mm wrench to remove (2) nuts. There is one nut located on the top of each. They do not need to come all the way off, just enough to allow the transmission mount and counterweight to be slide off of the transmission towards the rear of the car.

    9. Note the difference between the stock and the E21 mounts. the stock has a half moon cut out to fit into a nipple on the transmission cross brace. You have two options - either file the nipples down on the cross brace or remove some of the metal on the E21 mount to allow the mount to sit flat on the transmission cross brace. The material will need to be removed from the metal circle on the same side as the shorter thread..

    10. Use a drill to enlarge the holes in the transmission cross brace to allow for the wider M10 threads on the E21 transmission mount to pass through. If you use the counterweight, widen the holes here as well.

    11. File down the threads on the E21 transmission mounts on the longer side of the threads. The thread needs to be shaven down close to the body of the mount to allow it slide into the "C" shape lip on the rear of the transmission. Continue to test fit sliding the mount into the lip to ensure it fits. The threads need to be shaven down from their 10mm diameter to 8mm to match the stock mounts. You only need to file down 3-4 threads, enough to allow the mount to slide into the lip.

    12. Install the new mounts. Be sure the mounts sit flush on both the transmission and the transmission cross brace.

    13. Reinstall the heat shield, exhaust, and under-trays.

    2005 ///M3 6MT Coupe Imola/M-Texture

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