Transmission troubles

Hi readers,
I bought a GMC Safari van from 1984. Some dude's tried to build in a VORTEC 6 cylinder ( blazer 1994) engine but thy failed on the electrics. It was in
a garage for over 5 years now. Since I bought it I mounted an original TBI 6 cylinder from a blazer s10 1987 with a complete cable tree from a Astro van 1987, found on a scrapyard. The main problem was to get the speedo going, the transmission those guy's used had an electronic one and the cable-tree I found had a mannuel speedo. What I did was to get me the complete transmission from that Astro van so I did'nt have to search fo the right cable and try to get it going, the "old" trans had also a bit brownish oil and was smelling badly. Now to the point: The "new" transmission is from a 1987 Chevy Astro van, with overdrive ( 4 speed) I suppose it's a 700. I mounted it, refeshed the filter and the oil, and reajusted the kickdown cable. But it still kept shifting late. Now I drove it for about 1500 mls. refreched the oil and filter again, the collor was bright red and had a normal smell, in the drip pan was no sludge or other parts witch don't belong there. After this, the first 100 miles where ok I had a complete other car but now it starts late shifting again. What could it be?? By the way i dont know if the right dipstick is used. It was missing from the scrapyard and now i used the one with was in that "old" trans.
If you have anny sugestions please let me know. Thanks and take care. Marcel van de Riet,
snipped-for-privacy@wxs.nl snipped-for-privacy@planet.nl
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Synthetic transmission fluid is the best " tonic" going.
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