'84 300SD. New modulator. Still shifting hard.

I just put a new modulator in the transmission. Went well. However, the hard shifts didnt get any better (Up and down. A real clunk into 4th). It seems to jump from first, stop half a beat in second, before
settling into third. So I took off the vacuum line to the modulator and checked it visually and when I sucked on it, it seemed to hold vacuum. Yes, I know. Not a great test but it has helped me find broken lines in the past. I disassembled the banjo fitting at the back of the engine and unplugged it. I turned the modulator adjuster almost a turn CCW and nothing seemed to change except the rapid shift from one to three. The manual I have tells me nothing about the tranny except how to change the fluid and filter. Any ideas? Thanks!
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You didn't mention the rapid shift from 1st to 3rd gear. This is a positive sign that your transmission need rebuild. Every transmission that I had this problem... was solved with rebuilt or used transmission.
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Thanks for the input. Is there good source, online or otherwise, for rebuilt or used transmissions? I'm in Oregon, if that matters. Thanks again.
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This place is one of the best. My friend did buy one 722.6 transmission from him. If you have a friend with a shop, you can get lower price.
http://silverstartransmission.com/transmissions.htm
There is one seller on ebay from CA asking $1100. I don't know anything about him. In any case, don't buy transmission from Phoenix transmission... which has online and ebay listing... I hear horror stories about them..
At this time, it is extremely hard to find a reliable source of used transmission... The problem is finding out if it has been rebuilt or not... don't buy original condition transmission as it is super old now regardless of mileage.
wrote:

Thanks for the input. Is there good source, online or otherwise, for rebuilt or used transmissions? I'm in Oregon, if that matters. Thanks again.
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Pull the vacuum line to the tranny altogether and let it suck air. Now drive it aNd let me know how the tranny acts. It may ned a rebuilt but a) it may not b) some "rebuilding" you can do in place like k1 springs.
Need more info though.
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On Jun 9, 5:26pm, snipped-for-privacy@news.vrx.net (Richard Sexton) wrote:

Thanks for the replies. Sorry to take so long to get back here. I pulled the vacuum line and it shifted very hard. Especially shifting down.
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