There's lots of talk about transmission flare, I don't have that, or a 2-1 downshift clunk, don't have that either. What I experience is a rear end clunk on the upshift, most noticeable on the 3 to 4 shift. It seems as if perhaps it is not so pronounced when accelerating swiftly, when presumably the driveline is under more load. At light "throttle" it can be quite a thump, again felt apparently from "back there".

Bad flex disk? I didn't see anything obviously wrong with it when I had a look under there a couple of weeks ago.

Kevin

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'85 300SD

How are the 1-2 and 2-3 upshifts? Are they also quite "firm". If so, maybe you could have a loss of vacuum to the trans.

Set up a vacuum gauge and T it into the line down to the trans. Set it up so that you can read it while you drive. The gauge should start out high, near 15" or so, and drop as you step into the pedal. If it is at 6", or below, all the time, you have a vacuum problem that needs resolution.

If the shifts are softened by the increased vacuum, the "clunk" should disappear.

I guess there's no alternative but to get a vacuum gauge hooked up to know for sure. The other upshifts don't usually feel bad, but I can really feel the 3-4 shift from right back at the diff. There's no vibration at speed from anywhere, and absolutely nothing on the downshifts.

Kevin

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'85 300SD

I'd be dead without my combination vacuum/boost gauge. I must use it at least once every two months for these two. Once you get all the hoses and fittings sorted, one time, you are all set for the future.