Originally posted by Class85GT
OK, first thats a total contradiction. The AOD will be a four speed trans and I didn't think the 83 trucks had it but I'm not a guru on these or anything.
Assuming that you have a three speed trans there should be a vacuum hose that goes from manifold vacuum down to the pass side of the trans close to where the crossmember mount is. There'll be a vacuum modulator there and that's what causes early part throttle upshifts on these. Basically the modulator bleeds off internal trans pressure which then allows the governor to move easier and you get earlier upshifts. This assumption is kinda backed up by the delayed shift you mention. Without vacuum on the modulator the three-speeds would act like you've got the throttle wide open.
The AOD, OTOH, uses the TV linkage to INCREASE internal pressures and delay upshifts. So if you drive an AOD with the TV linkage or cable disconnected/what have you and internal pressure doesn't rise you get a very early and soft upshift. To the point of burning up the trans in short order.
I suppose there is one possible way of getting and AOD to shift late. If the linkage falls back to the max pressure position due to its own weight, an AOD would shift late and engage REALLY harshly. If you can pull the linkage forward then try to rig a spring to hold it forward and see what you get.
Personally I think you got a three speed and that linkage is for kickdown only and shouldn't follow the throttle like an AOD must. Kickdowns usually only touch the throttle arm above 50 percent throttle and have to get almost all the way to WOT before the trans will kickdown.
Do a little poking around and get back to us.