I had to rebuild my vacuum pump, before the rebuild,
transmission would shift at WOT at 25 mph, 35 and 57.
After the rebuild, trans shifts at 18, 28 and 50.
What gives? The car is a 1978 300d. it had very good
take off before the rebuild but now with it shifting
at such low speeds it sure is a slow trud. Is the pump
pulling so much more vacuum now that is is causing the
trans to shift sooner. If so how do I correct it.
Thanks for any help anyone can give. Norm

Does your car have a bowden cable. I don't remeber is the early models do or not. If it does it is connected the linkages on the top of the valve cover. Try adjusting it. Since you rebuilt your vac pump the vac system is much stronger so the transmission modulator is getting different amounts of vac now. Come to think of it you may need to adjust the vacuum control valve.

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Yes, you are creating more vacuum. Vacuum is what induces the tranny to shift.
{on your model you don't have a Bowden cable or a vac control valve}
On a '78 model, I believe you are going to have to rotate the pin inside the tranny modulator. On that year I believe it is located on the passenger side of the tranny. Just follow the vac line down to the tranny, and that will help you find it. I believe it is red/orange on yours, but I could be wrong.
Only turn the pin one notch at a time, then go drive it around and see how it shifts. There is a cap on the end held on by a snap ring. Just use needle nose pliers to squeeze the ring together and pull the end off. You will then see a little rectangular type pin. Pull out only a little ways, (just mm's), rotate it one notch and push back in.
I will look for my old info to see which direction does what.
My old '80 wagon could be dialed in to where one notch in one direction would shift good but later, and one the other direction shifted good but earlier. I would just drive up on ramps, make the adjustment, back off ramps and drive down the road. After you see how to make the adjustment, it only takes about a minute to crawl under there and do it.
I'll run off and look for the proper direction and edit back.
**edit** Good thing I keep notes with my memory. CLOCKWISE with the pin firms up the shifts.
Note: only turn one notch at a time. Keep a count of where you start, and the subsequent number of pin moves, just in case you want to go back to baseline.
In my notes from my old wagon, on the bottom of that page I had "Best the car has ever driven!". Little did I know of the smoking saga that was to follow.....
Your results may vary............

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Tanks jimmyl this I shall give a try.