Thanks for those who have posted in the past, this has been a end of the rainbow plethora of information. I am very much indebted.

Now for my Brain teaser: I have a300sd 1982

seems my 4th gear doesn't like when I use the air conditioner, at least not until i have driven the car for several miles.

Without using the a/c, the tranny is a little rough shifting from 1st to 2nd, but works thru all gears effortlessly.

My thought is there is a draw on the vacuum when using the a/c, but why???

Likewise when I use the heater, the car will not shut off except using manual button in engine compartment.

You will probably want me to test the vacuum pull from the pump? which i have yet to do.

Thoughts?

All are welcome

Two potential issues:

1. The climate control systems on these vehicles are notorious for vacuum leaks. Remove the Green colored hard vacuum line from the "starfish" rubber connector and plug it with a natural wood golf tee or a plastic golf tee. Don't use a painted tee as the paint can flake off into the vacuum system.

Somehow the fact that the climate control system is drawing vacuum away from the tranny may be affecting the shift quality.

2. Engine power is reduced by about 10% when the AC compressor is engaged. The reduction in engine power may be affecting the shift.

Start by blocking off the vacuum line in #1, as this is the more likely culprit.

when you say "doesn't like 4th gear" do you mean that the tranny refuses to shift, or is it flaring (revving way up before going into 4th gear after disengaging from 3rd gear)

If I knew what kind of car you are driving, I might be able to give more specific advice.

Sorry for the lack of info

Its an 82 300 SD. Yes the trans flares without shifting.

Hey guys.

If you could provide a little help for a newbie.

The starfish connector Dawson speaks of in 1
above....Where is that located?

BTW I have an 82 300 sd.

Thanks in advance!!

I believe reducing vacuum should tighten shifts and reduce flaring. So, if your transmission is flaring more, this would seem to indicate higher vacuum to the modulator.

__________________
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

where is the starfish connector Dawson speaks of above???

Thanks

Is anybody out there?

Don't have an SD, but I suspect that the item being mentioned is a black rubber 4-way tubing connector. This would be located under the hood on drivers side of the engine.

__________________
1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

Thanks for your help
jk

Quite coincidentally, I had an 83 Firebird that did something very similar to this but it was the other way around. It would only shift normally through all the gears only if the A/C was on.

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012