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Any recent repair work done to the transmission like a fluid change or other repair? Do you have all forward gears? Is the gear box fault warning on?
Since there is no dipstick it is a pain to check and add fluid. First the transmission fluid needs to be warmed up to 30-40 degrees C (85-105 degrees F) then there is a fluid level check plug which is located next to the shifter cable under the metal cover. This will either be an allen plug or 14mm. If fluid runs out of this plug in a steady stream it is full. To add fluid remove the rubber plug from the top of the front pan under the battery and add fluid through that port using a long funnel with a hose on the end of it.
can this drum be replaced by pullling the rear cover? and can yoou give me a part number for a new drum
Unfortunately the transmission will need to be removed to replace the drum and inspect the brake band. Here is the Jatco parts list.