1984 300D Transmission is Slipping

[LEDer1]

1984 300D

From a stop slips through first gear.

When driving 5mph up a steep hill, will downshift into first and climb the hill fine.

When parked with parking break engaged, won't slip.

I am ordering the vacuum switchover valves, as the levers are worn off.

Plenty of vacuum at the check valve on the booster line.

15" drops to almost zero when accelerating, at the valve on top of the injection pump.

The line to the modulator holds vacuum.

Doors lock fast, car shuts off, brakes work great.

If I power brake it a little before starting out, first gear engages fine until next stop.

Red trans fluid, no burnt smell.

Can defective switchover valves cause this problem?

Any other vacuum I should test?

Also, this wasn't a problem that got worse over time. I parked it on Monday and it had driven fine, and on tuesday BAM just started slipping. I have 500 miles on the car since and things have gotten no worse.

Also, when a shop was replacing the master cylinder, they broke the orifice off the check valve on the booster line, and rigged it with an old piece of vacuum line (I since have replaced the entire vacuum booster line). Could that hack fix have affected my transmission?

[leathermang]

First, when was the trans fluid AND filter last changed ?

the recommended change rate is fewer miles than most other cars... so many miss it...

then before doing too much else... search for ' trans-x ' in the archives... follow directions on the can if you try it...

[vstech]

since your 1st gear engages fine on down shifts, I don't know, but the B2 piston does actuate 1st gear... perhaps your seal is leaking and not building enough pressure from idle to move the piston...

[LEDer1]

I changed fluid and filter about 3 weeks ago. I thought I had a clogged filter.
Old fluid was red, not burnt, and no metal in the pan. I'll check into the trans-x..

Originally Posted by leathermang

First, when was the trans fluid AND filter last changed ?

the recommended change rate is fewer miles than most other cars... so many miss it...

then before doing too much else... search for ' trans-x ' in the archives... follow directions on the can if you try it...

[vstech]

Originally Posted by LEDer1

I changed fluid and filter about 3 weeks ago. I thought I had a clogged filter.
Old fluid was red, not burnt, and no metal in the pan. I'll check into the trans-x..

what fluid did you use?
the newer devcon VI is not recommended in these older transmissions.
and the mobil1 fluid is not either...

[LEDer1]

Originally Posted by vstech

what fluid did you use?
the newer devcon VI is not recommended in these older transmissions.
and the mobil1 fluid is not either...

I will have to check on the type of trans fluid; my buddy owns a texico xpress lube, so I used what he had there.

Problem seems exactly the same, before and after fluid filter change, no better no worse..

[LEDer1]

Dex 3 is what the shop told me for trans fluid.

I did put in Trans-x, which made things better, but still slips.
;

Today, I adjusted the Bowden Cable, using the throttle rod on the IP as a reference, which took me about 5 turns in to match 'no free play' with the initial movement of the throttle rod.

Now the 300D is a totally different car, still slips, but shifting after it catches second is perfect 'luxurious'.

B2 piston?

thank you for taking the time to help me. I have been taking pictures, and I will post a album soon.

[mikethezipper]

I was wondering if you had any updates on this, as my car is having the exact same issue.
It used to only do it in the wintertime, but now it is all the time. Everything I have read about the B2 piston is that it will just not go into first altogether, but mine does go to first fine when I am downshifting into it from second, it is just getting there ( to second gear) that is the issue.

[Skippy]

1. Remove and discard automatic transmission.

2. Install manual transmission, generally sourced from a manual 240D.

I did this and it solved all my transmission issues in my 300D.