Okay this is what I have noticed the car does not jerk when I push the accelerator. It shifts smooth through all the gears. It jerks if I am coming to a stop and mash the accelerator between 20 and 40 MPH. If I come to a complete stop and floor it it shifts smooth or if I go easy it shifts smooth. I really do not think it is the differential because at 180,000 that thing should not even be broken in. I don't know. Maybe it is a vacuum issue or maybe the trans fluid needs changed. I know my door locks are not working at all and the center vents have heat which I am sure they should not so If I have a massive leak in the locks can I just plug them off. I replaced all the rubber ends on the vacuum hoses on the engine. I looked at the flex disc and it was tight and the drive shaft has no play. Worries me any sugggestions will be appreciated.

Thanks,
Dieselman

Yes, vacuum looks can cause hard shifting, particularly downshifting. Plug the lines. Yellow/red line is the doors. Plug it in the engine compartment.
If the center vents have heat, someone has probably wedged them open because without vacuum they should be closed. Still could be a leak in there. Can reach and plug that line through the glove compartment.
I have a leak in my foot well vent diaphragms so when I have the heat on, my TD downshifts hard. So I have to remember to turn the heat to defrost before coming to a stop.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Well it did jerk when I was coming to a stop really bad. The back end clunked really bad so I adjusted the modulator on the trans. This jerk is when I moving at between 20-40 MPH if I press the padel quickly it jerks into gear. I am confused


Dieselman

The cluck at a stop is caused by no or not enough vacuum.

1. Check the line to the modulator with a MityVac and see if it holds. If not, you can replace the rubber cap, which sometimes leaks.
2. If it is holding vacuum, next check the amount of vacuum that is being fed to the modulator at idle and then slowly open the throttle. The vacuum should start at about 15 lbs and drop in a reasonable ratio to throttle (7.5 lbs at 1/2 throttle) etc.

My guess is that you either don't have enough vacuum at idle or as soon as you crack the throttle it drops lower than it should.

If you vacuum is low at idle, it can either be a vacuum leak, the vacuum pump not producing enough vacuum or the transmission leak system is not adjusted properly. The transmission leak system consists of 2 white plastic valves under the cover attached to the valve cover and another white valve mounted on the IP (about the size of a child's fist.

To confirm the source of the issue, disconnect all feeds off of the main vacuum line and cap any openings to that line, the exception being the one the MityVac is hooked up too. To insure the leak is not in the power brake booster, you would need to plug the end of the line with something.

Note: Your engine will not shut off by the key, until everything is reconnected to the main vacuum line.

Don

__________________
1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it

I think it's a vacuum issue also, as I have had the same problems on a coup[le of these cars.
Do what the other gentleman said about locating the vacuum leak and you should be O.K.
Good luck, Adam

Thank everyone for the responses I will try them.

Thanks Again,

Dieselman